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Quantitative relationship between microstructure and tensile properties of Al-Zn-Mg-Cu alloys with various alloying degrees
Abstract
A quantitative relationship between microstructure and tensile properties of Al-Zn-Mg-Cu alloys with various alloying degrees was investigated in this study. Three kinds of high strength Al-Zn-Mg-Cu alloys with little strength difference were used for the microstructural characteristic and statistical analysis. A strength model with high accuracy was established through the systematical calculation of strengthening theories, which was validated by the microstructure and ultimate tensile strength of a testing sample. The model gives the precise ratio of the contribution of precipitation hardening and even the component achieved from the bypass mechanism. Moreover, guidance on the regulation of precipitation phases was proposed from the strength model. It can be disclosed that the alloys will show the best strength when the precipitates of 7xxx series Al alloy are distributed near the right of critical radius, which is identified as 2.5 nm in this model.
... Furthermore, the size and shape of precipitates are also important for the strength during thermal deformation. Based on the classic strengthening theory of metals [38,39], there are two mechanisms between dislocations and precipitate during alloy deformation, Furthermore, the size and shape of precipitates are also important for the strength during thermal deformation. Based on the classic strengthening theory of metals [38,39], there are two mechanisms between dislocations and precipitate during alloy deformation, there are cutting and bypassing. ...
... Based on the classic strengthening theory of metals [38,39], there are two mechanisms between dislocations and precipitate during alloy deformation, Furthermore, the size and shape of precipitates are also important for the strength during thermal deformation. Based on the classic strengthening theory of metals [38,39], there are two mechanisms between dislocations and precipitate during alloy deformation, there are cutting and bypassing. When the precipitate is small in size and maintains a coherent relationship with the matrix, dislocations are mainly cut through the precipitates. ...
The hot tensile behavior of an extruded 6082 alloy sheet at varying temperatures and strain rates was investigated by a Gleeble3500 thermal simulation testing machine. The optical microscope (OM), scanning electron microscope (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were applied to observe the microstructure evolution. It is found that the flow stress of the studied alloy declines with increasing deformation temperature. When deformed at high temperatures, the density of dislocation decreases obviously. In addition, precipitate coarsening occurs, resulting in a decrease in deformation resistance. The dimple number of the fracture samples increases with temperature and the size of the dimple becomes deeper, exhibiting an excellent plasticity. The 6082 sheet presents anisotropy of mechanical behavior at 300 °C, this can be attributed to the fibrous grain and the Brass component {011}<211>. The anisotropic behavior seems to be slighter with an increase in temperature. No obvious anisotropic behavior was found when tensiled at 400 °C. Because it is easier to activate the slip system at elevated temperatures, meanwhile, the recrystallization begins to occur at 400 °C.
... a is a variable for fcc metals, G is the shear modulus (26.9 GPa) for 7075 Al, and q is the dislocation density (Ref 9). The two most recognized manifestations of precipitation/ dispersoid strengthening are Orowan dislocation bypassing and dislocation shearing mechanisms ( Ref 9,[29][30][31][32][33][34]. In this work, the coarse precipitates were governed by the Orowan dislocation bypassing mechanism considering that their average diameter was well over the critical radius (2.1 nm) ( Ref 29,31). ...
... The two most recognized manifestations of precipitation/ dispersoid strengthening are Orowan dislocation bypassing and dislocation shearing mechanisms ( Ref 9,[29][30][31][32][33][34]. In this work, the coarse precipitates were governed by the Orowan dislocation bypassing mechanism considering that their average diameter was well over the critical radius (2.1 nm) ( Ref 29,31). The yield stress increment caused by precipitates was determined by the following formula. ...
... A widely recognized approach to enhancing the overall performance of Al-Zn-Mg-Cu series aluminum alloys involves modifying their elemental compositions. Zinc (Zn) and magnesium (Mg) are the primary strengthening elements within these alloys [9][10][11]. After aging treatment, these elements precipitate strengthening phases, specifically η ′ (MgZn 2 ) and T (Al 2 Mg 2 Zn 3 ), which significantly contribute to the strength of material. ...
Aluminum alloy 7050-T74 with varying zinc-to-magnesium (Zn/Mg) mass fractions was synthesized using melt casting and hot extrusion techniques. This study investigated the influence of different Zn/Mg ratios on the microstructure, mechanical properties, and corrosion resistance of the alloy. Light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile testing, and corrosion testing were employed as analytical methods. The findings indicate that as the Zn/Mg ratio increases from 2.36 to 3.84, the proportion of low-angle boundaries (LABs) within the alloys initially rises and then decreases, achieving a balance between high strength and favorable elongation. Specifically, at a Zn/Mg ratio of 2.72, the alloy exhibits a tensile strength of 641 MPa, a yield strength of 609 MPa, and an elongation of 10.1%. Additionally, increasing the Zn/Mg ratio to 2.90 slightly reduces intergranular corrosion resistance while enhancing exfoliation corrosion resistance.
... where g is the contribution value of fine-grain strengthening, which is determined by the average grain size and can be estimated by the equation of = k d g y 1/2 (where k y is the grain boundary barrier coefficient of 0.12 MPa·m 1/2 ) [54,55]. M is the Taylor factor, which is 3.06 for the FCC metals [56]. ...
In this study, AA7075 sheets were processed by cryorolling and room-temperature rolling respectively, and subsequent aging. The microstructure evolution and mechanical properties of AA7075 sheets were investigated by hardness measurements, tensile tests, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Results show that with the rolling reduction ratio of 80%, the room-temperature rolled samples had massive edge cracks, while the cryorolled samples were in good shape and without any cracks. The improved ductility of materials in cryogenic environments, the reduced precipitation and the absence of shear bands in sheets during cryorolling contributed to the reduced edge cracks. Compared to solution treated samples, the yield strength and ultimate tensile strength of cryorolled samples were increased by 155% and 44%, respectively, and the elongation decreased as a loss, which is obviously better than that of room-temperature rolled samples. After the subsequent aging treatment, the strength and ductility of the rolled samples were simultaneously improved, the yield strength of cryorolled + peak-aged sample was increased by 44 MPa and the elongation was increased by 68% compared with those of the cryorolled samples. Compared with room-temperature rolled + peak-aged samples, the strength of cryorolled + peak-aged sample was higher, and the elongation to failure and uniform elongation were increased by 58% and 72%, respectively. Numerous nanosized GP zones and η' phases were precipitated after aging, and the precipitation strengthening is the main contributor to the strength enhancement of the samples after aging. The improved ductility of cryorolled + peak-aged samples is mainly due to the combined effect of dislocation annihilation, uniform deformation and fine precipitates in them.
... Tabel 4. Komposisi Kimia pada Pengujian Paduan Aluminium (Gao et al., 2022) ...
Selama beberapa waktu terakhir paduan aluminium semakin banyak digunakan karena sifat-sifat yang menguntungkan. Kemudian, banyak proyek penelitian dilakukan dengan tujuan untuk mendapatkan lebih banyak pemahaman yang komprehensif tentang kinerja struktural untuk mengembangkan formula desain yang akurat dan andal. Ruang lingkup makalah ini adalah untuk memberikan tinjauan penelitian komprehensif yang dilaporkan pada paduan aluminium. Makalah ini menyajikan gambaran tentang studi penelitian tentang sifat mekanik dengan uji tarik dan uji kekerasan paduan aluminium, serta pengaruh penambahan Cu, Zn, dan Mg untuk memperkuat sifat mekanik dari Al. Hasilnya menunjukkan peningkatan efek penguatan dengan peningkatan kandungan Cu. Sedangkan kekuatan paduan menurun dengan meningkatkan rasio Zn/Mg. Saat kandungan Cu meningkat, kekuatan tarik, hasil kekuatan, dan perpanjangan meningkat. Sedangkan kekuatan tarik, kekuatan luluh, dan kekerasan penurunan dengan peningkatan rasio Zn/Mg.
Al–Zn–Mg–Cu alloys are widely used in aerospace, with recrystallization significantly influencing their stress corrosion resistance. This study examines the impact of recrystallization morphology on corrosion resistance in a high‐alloying Al–Zn–Mg–Cu alloy, focusing on lath‐shaped and equiaxed recrystallized grains. The findings reveal that, at the same recrystallization fraction, the equiaxed sample has a 2.83 times higher corrosion current density and a 1.15 times higher stress corrosion cracking susceptibility index than the lath sample. However, its critical stress intensity factor is only 89.3% of the lath alloy's. Lath recrystallization demonstrates superior stress corrosion resistance due to larger grain sizes, wider grain boundary precipitate spacing, lower Zn and Mg content, and higher Cu content. Finite element simulations and in‐situ tensile tests show that the equiaxed sample experiences more stress concentration and cracking at grain boundaries under the same applied stress. These results provide insights into optimizing the stress corrosion resistance of Al–Zn–Mg–Cu alloys.
Hot deformation is a crucial process in the manufacturing of aluminum alloy products, as its parameters exert a profound influence on the ultimate properties of the alloys. This work reports on the Al-Zn-Mg-Cu alloys at a deformation temperature of 450°C, a deformation rate of 5 mm/s, and deformation degrees of 50% and 90% in industrial settings. Following that, an extensive assessment of the alloys’ mechanical characteristics, including their fracture toughness, tensile strength, and fatigue performance. Furthermore, a quantitative analysis of the microstructure was undertaken using OM and EBSD, which revealed that both the average and sub-grain sizes of the two alloys exhibited comparable characteristics. However, the recrystallization fraction showed a difference, with the alloy deformed to 90% exhibiting a higher fraction than the alloy deformed to 50%, while these recrystallized grains are distributed in chains. With the increase of deformation degree from 50% to 90%, the yield and ultimate strengths increase slightly. The opposite law is demonstrated by fatigue crack propagation resistance and fracture toughness. Put otherwise, compared to the alloy deformed to 50%, the alloy deformed to 90% exhibited a faster rate of fatigue crack propagation and a lower fracture toughness. In summary, this research examines how the degree of deformation affects the mechanical characteristics and microstructure of Al-Zn-Mg-Cu alloys.
Different solution treatments for annealed 6061 aluminum alloy were performed using an orthogonal testing method. The effects of solution treatments on the microstructure and mechanical properties of the alloy were investigated by employing techniques such as electron backscatter diffraction and tensile tests. The effects of changes in the size and area fraction of the soluble phase on solid solubility, dislocation evolution, and recrystallization were explored. A microstructure evolution model for the solution-treated alloy was developed, and the contributions of different strengthening mechanisms were quantified. The results indicate that the optimal solution treatment parameters were treatment at 570 °C for 3 h, followed by water quenching. After treatment, Mg2Si dissolves into the matrix, increasing the solid solubility and fraction of recrystallized grains while reducing the dislocation density. All solution-treated alloys, except those quenched in a furnace, displayed notable increases in strength with minimal loss in ductility. The water-quenched alloy exhibited the best overall mechanical properties, with the yield strength and ultimate tensile strength increasing by 139.4 and 128.1%, respectively, compared to those of the untreated alloy. Analysis of the strengthening mechanisms revealed that the primary contributors to improved alloy strength are dislocation and grain boundary strengthening.
Additive manufacturing provides an efficient way of producing metallic components with complex geometries. Their microstructure is substantially different to those from conventional processing, creating opportunities for manipulating the final microstructure and properties via heat treatment. Here, we demonstrate that as-built heterostructures in an Al-Zn-Mg-Cu-Nb alloy produced during the solidification of molten pools provide a driving force and additional Zener pinning sources for recrystallization. This creates a bimodal grain structure after solution treatment, causing additional hetero-deformation-induced strengthening and hardening. Coarse grains are found to promote work hardening and blunt the propagate of cracks during deformation, increasing ductility. Together with precipitation strengthening from a high number density nanoprecipitates, the simultaneous improvement of strength and ductility in a highly alloyed Al-Zn-Mg-Cu-Nb alloy is achieved. These results provide a simple strategy for the development of additively manufactured age-hardening alloys with improved strength and ductility for high performance structural applications.
To explore the influence of deformation temperature on the tensile and microstructure of high-strength Al alloy, pre-aged AA7075 sheets were processed by cryorolling and room temperature rolling. Hardness and tensile tests examined the mechanical properties of AA7075. The microstructures of AA7075 under different rolling conditions were analyzed by scanning electron microscopy, optical microscopy, x-ray diffraction, electron backscatter diffraction and transmission electron microscope. The results show that the ultimate tensile strength and hardness of cryorolled AA7075 are 672.6 MPa and 226.6 HV, respectively. When the rolling reduction rate reaches 60%, the cryorolled AA7075 remains great ductility of 5.7%. The cryorolling can effectively result in higher dislocation densities, thus improving the strength of the AA7075 sheets. Meanwhile, the cryorolled AA7075 after pre-aging can avoid the occurrence of shear bands and microcracks to improve the material's ductility.
In this work, the effect of Zn content on the formability and aging precipitation of Al–Zn–Mg–Cu–Nb alloys prepared by laser powder bed fusion (LPBF) were investigated via experiments and in-depth characterization. Results show that the increase in Zn content narrows the LPBF processing window, owing to the significant evaporation of Zn element during LPBF. The increase of Zn content not only accelerates the aging kinetics of Al–Zn–Mg–Cu–Nb alloys, but also increases the number density of nanoprecipitates and reduces the PFZ width, resulting in an enhancement in the peak microhardness. The microstructure evolution and aging behavior of alloys during direct aging (DA) and traditional solution treatment and aging (STA) were compared. DA can maintain fine equiaxed grains, while a bimodal grain structure with coarse and fine grains can be obtained after STA. The peak microhardness and the number density of nanoprecipitates in alloys treated with STA is higher than that of alloys treated with DA, which indicates that the traditional STA heat treatment is still applicable to Al–Zn–Mg–Cu–Nb alloys fabricated by LPBF.
Aluminum alloys with ultra-strength and high-toughness are fundamental structural materials applied in the aerospace industry. Due to the intrinsic restriction between strength and toughness, optimizing a desirable combination of these conflicting properties is always challenging in material development. In this study, 171 sets of data were curated based on the characteristics of high-strength and high-toughness aluminum alloys in the literature. Then, a machine learning design system (MLDS) with a property-oriented design strategy was established to rapidly discover novel aluminum alloys with ductility and toughness indexes (with elongation δ=8%–10% and fracture toughness KIC=33–35 MPa·m1/2) comparable to those of current state-of-the-art AA7136 aluminum alloys when the ultimate tensile strength (UTS) exceeded approximately 100 MPa, with values reaching 700–750 MPa. With the MLDS for experimental verification, three typical candidate alloys show satisfactory performance with UTS of 707–736 MPa, δ of 7.8%–9.5%, and KIC of 32.2–33.9 MPa·m1/2. The high contents of Mg and Zn alloying elements in the novel alloys form abundant η′ phases, which produce a significant hardening effect, while the reasonable matching of Cr, Mn, Ti and Zr dispersoids refines the grain size. The decreased Cu content compared with that in the AA7136 alloy inhibits the formation of the σ phase and S phase, so that the alloys show high toughness.
The effects of Zn/Mg ratios on microstructure and mechanical properties of Al-Zn-Mg-Cu alloys aged at 150 °C have been investigated by using tensile tests, optical metallography, scanning electron microscopy, transmission electron microscopy and atom probe tomography analyses. With increasing Zn/Mg ratios, the ageing process is significantly accelerated and the time to peak ageing is reduced. T′ phase predominates in alloys of lower Zn/Mg ratios while η′ phase predominates in alloys with a Zn/Mg ratio over 2.86. Co-existence of T′ phase and η′ phase with a large number density is beneficial to the high strength of alloys. Such precipitates together with narrow precipitate free zones cause a brittle intergranular fracture. A strength model has been established to predict the co-strengthening effect of T′ phase and η′ phase in Al-Zn-Mg-Cu alloys, including the factors of the grain boundary, solid solution and precipitation.
The natural aging (NA) response of a commercial Al-Zn-Mg alloy has been tracked to investigate the effects of solute clusters on its mechanical properties. It has been observed that the increase of yield strength during NA is not accompanied by the degradation of uniform elongation due to the simultaneously enhanced strain hardening ability. As a consequence, the Al-Zn-Mg alloy with dense solute clusters shows a comparable yield strength, better strain hardening ability and uniform tensile strain relative to its artificially aged counterparts containing precipitates. This positive effect of solute clusters on strain hardening has been systematically studied by tracing the microstructure evolution during deformation through synchrotron X-ray diffraction and atom probe tomography. We found that the dislocation multiplication dominates over the entire deformation process until failure in NA alloys; however, no effect of solute clusters on the dislocation density evolution can be identified. On the other hand, solute clusters themselves dramatically evolve, showing a dissolution-to-coarsening transition during deformation, which can be understood on the basis of a kinetic model. The experimental evidence strongly suggest that the dislocation storage and strain-induced evolution of solute clusters are insufficient to account for the observed high strain hardening rate, and the contribution from other possible mechanisms are estimated in a semi-quantitative manner.
To clarify the influence of a pre-ageing treatment on precipitation behaviors in the AA7075 aluminum alloys with ultrafine grain (UFG) structure, the alloys were pre-aged prior to a room temperature rolling process (PA + RTR). The precipitation kinetics in PA + RTR alloys during isothermal heat treatment at 100 °C were systematically investigated by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and Vickers hardness measurements compared to its counterpart without pre-ageing treatment (i.e. RTR). Results reveal the pre-ageing treatment can lead to a higher dislocation density (22.8 × 1014 m−2) and a larger concentration of Mg (~12.85 at.%) and Zn (~8.33 at.%) atoms in the vicinity of dislocation, which causes a considerable increase in the size and volume fraction of the precipitates in PA + RTR alloy. Specially, our study shows, for the first time, that many GPII zones come from second nucleating in PA + RTR alloy at 108 h, which may ascribe to the pre-ageing treatment. More importantly, the pre-ageing treatment not only makes both two hardness peaks of PA + RTR alloy appeared ahead of but also higher than those of RTR alloy, by virtue of the enhanced precipitation kinetics in PA + RTR alloy. Keywords: Ultrafine grain, Aluminum alloys, Precipitation kinetics, Pre-ageing treatment, Small angle X-ray scattering, Microstructure analysis
Stress corrosion cracking (SCC) is degradation of mechanical properties under the combined action of stress and corrosive environment of the susceptible material. Out of eight series of aluminium alloys, 2xxx, 5xxx and 7xxx aluminium alloys are susceptible to SCC. Among them, 7xxx series aluminium alloys have specific application in aerospace, military and structural industries due to superior mechanical properties. In these high strength 7xxx aluminium alloys, SCC plays a vital factor of consideration, as these failures are catastrophic during the service. The understanding of SCC behaviour possesses critical challenge for this alloy. The main aim of this review paper is to understand the effect of constituent alloying elements on the response of microstructural variation in various heat-treated conditions on SCC behavior. Further, review was made for improving the SCC resistance using thermomechanical treatments and by surface modifications of 7xxx alloys. Apart from a brief review on SCC of 7xxx alloys, this paper presents the effect of stress and pre-strain, effect of constituent alloying elements in the alloy, and the effect of environments on SCC behaviour. In addition, the SCC behaviours of weldments, 7xxx metal matrix composites and also laser surface modifications were also reviewed.
The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg(-Cu) system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure–property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high-temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches. In each case, the effects on both the microstructure and the resulting properties are discussed.
The effect of substituting 0.01 or 0.02at.% Er for Sc in an Al–0.06 Zr–0.06 Scat.% alloy was studied to develop cost-effective high-temperature aluminum alloys for aerospace and automotive applications. Spheroidal, coherent, L12-ordered Al3(Sc, Zr, Er) precipitates with a structure consisting of an Er-enriched core surrounded by a Sc-enriched inner shell and a Zr-enriched outer shell (core/double-shell structure) were formed after aging at 400°C. This core/double-shell structure strengthens the alloy, and renders it coarsening resistant for at least 64days at 400°C. This structure is formed due to sequential precipitation of solute elements according to their diffusivities, D, where DEr>DSc>DZr at 400°C. Zr and Er are effective replacements for Sc, accounting for 33±1% of the total precipitate solute content in an Al–0.06 Zr–0.04 Sc–0.02 Erat.% alloy aged at 400°C for 64days. Er accelerates precipitation kinetics at 400°C, resulting in: (i) strengthening due to the elimination of lobed-cuboidal precipitates in favor of spheroidal precipitates; and (ii) a decrease in the incubation time for nucleation because DEr>DSc. Finally, a two-stage aging treatment (24h at 300°C+8h at 400°C) provides peak microhardness due to optimization of the nanostructure.
An improved model is described to predict variations in fracture toughness of high strength aluminium alloys with volume fraction, size, and characteristics of the contained multiscale second phases, i.e. ellipse shaped constituents, sphere shaped dispersoids, and disc shaped precipitates, in an integrated manner. Results show that predictions are in broad agreement with values measured experimentally for an aged Al-Cu-Mg alloy. Furthermore, the model was employed torelate the anisotropic fracture toughness ofalloy plate to its orientation. A diagramis presented to illustrate the relationship between yield strength and fracture toughness of the aged alloy.
The topic of precipitation hardening is critically reviewed, emphasizing the influence of precipitates on the CRSS or yield
strength of aged alloys. Recent progress in understanding the statistics of dislocation-precipitate interactions is highlighted.
It is shown that Pythagorean superposition for strengthening by random mixtures of localized obstacles of different strengths
is rigorously obeyed in the limit of very weak obstacles; this had been known previously as a result of computer simulation
experiments. Some experimental data are discussed in light of this prediction. All of the currently viable mechanisms of precipitation
hardening are reviewed. It is demonstrated that all versions of the theory of coherency hardening are woefully inadequate,
while the theory of order hardening is capable of accurately predicting the contribution of γ′ precipitates to the CRSS of
aged Ni-Al alloys. It is also convincingly shown that a new theory based on computer simulation experiments of the motion
of dislocations through arrays of obstacles having a finite range of interaction cannot explain these same data, and is of
doubtful validity in other instances for which its success has been proclaimed. A new theory of hardening by spinodal decomposition
is proposed. It is based on the statistics of interaction between dislocations and diffuse attractive obstacles, and is shown
to be in very good quantitative agreement with much of the limited data available. Some of the problems that remain to be
addressed and solved are discussed.
A model for the yield strength of multi-component alloys is presented and applied to overaged Al–Zn–Mg–Cu alloys (7xxx series). The model is based on an approximation of the strengthening due to precipitate bypassing during precipitate coarsening and takes account of ternary and higher order systems. It takes account of the influence of supersaturation on precipitation rates and of volume fraction on coarsening rates, as well crystallographic texture and recrystallisation. The model has been successfully used to fit and predict the yield strength data of 21 Al–Zn–Mg–Cu alloys, with compositions spread over the whole range of commercial alloying compositions, and which were aged for a range of times and temperatures to produce yield strengths ranging from 400 to 600 MPa. All but one of the microstructural and reaction rate parameters in the model are determined on the basis of microstructural data, with one parameter fitted to yield strength data. The resulting accuracy in predicting unseen proof strength data is 14 MPa. In support of the model, microstructures and phase transformations of 7xxx alloys were studied by a range of techniques, including differential scanning calorimetry (DSC), electron backscatter diffraction (EBSD) in an SEM with a field emission gun (FEG-SEM).
The materials community in both science and industry use crystallographic data models on a daily basis to visualize, explain and predict the behavior of chemicals and materials. Access to reliable information on the structure of crystalline materials helps researchers concentrate experimental work in directions that optimize the discovery process. The Inorganic Crystal Structure Database (ICSD) is a comprehensive collection of more than 60 000 crystal structure entries for inorganic materials and is produced cooperatively by Fachinformationszentrum Karlsruhe (FIZ), Germany, and the US National Institute of Standards and Technology (NIST). The ICSD is disseminated in computerized formats with scientific software tools to exploit the content of the database. Features of a new Windows-based graphical user interface for the ICSD are outlined, together with directions for future development in support of materials research and design.
The ageing precipitates and strengthening effects of Al-Zn-Mg-Cu alloys with different Zn contents were investigated. The results showed that increasing Zn contents can significantly improve the age-hardening response and influence the type of precipitates as well. The low Zn-containing alloy (1.70 at.%) is strengthened by nano-scale T′ phases in the peak aged condition. However, the microstructure of the high Zn content (2.34 at.%) alloy in the peak aged condition consists of a higher density of globular T′ phases and a small proportion of plate-like η′ phases. The results of atom probe tomography revealed that clusters formed at the early stage of ageing with a Zn/Mg atomic ratio higher than 1.3 transform into η′ phases and these clusters with a lower Zn/Mg ratio transform into T′ phases. The composition of a T′ phase varies with its size, where the concentrations of Zn and Mg increase with its increasing radius, while the concentration of Al presents an opposite trend.
The addition of Ag significantly increases the early ageing response, overall ageing response and peak age-hardening of an Al-Zn-Mg-Cu alloy. Ag is the most segregated of the solutes during ageing and a positive correlation between Ag and Cu exists in clusters and larger aggregates throughout the precipitation sequence (1–120 min).
A modified powder hot extrusion including gas atomization, pre-compaction and hot extrusion was used to fabricate an ultrahigh strength Al-Zn-Mg-Cu-Zr-Sc (7055) alloy. The results reveal that a homogeneous microstructure containing fine grains and tiny second phases is formed after extrusion. The solution-treated alloy aged at 393 K for 24 h achieves peak hardness of 177 HB due to the common effect of GPI zone and η′ phase. The peak-aged alloy exhibits an ultrahigh ultimate tensile strength of 734 MPa and a good elongation at fracture of 9.8%, which is mainly attributed to fine grains and high-density nanoscale second phases (GP, η′ and Al3(Sc/Zr)). Micropore aggregation fracture is the main fracture mechanism in all the tested alloys states. The cracking or debonding of coarse second phases is the main cause of the limited strength of as-extruded alloy, while the coarse phases and PFZs at the grain boundaries are responsible for the decrease in the elongation of peak-aged sample. Compared with the 7055 alloys fabricated by other techniques, it is suggested that this modified powder hot extrusion may be an effective approach to develop high strength Al alloys.
As a new generation of Al-Zn-Mg-Cu alloy, 7085 aluminum alloy is a promising structural material in the field of aerospace industry. However, research on its thermal stability is still lacking. In the present work, thermal exposure was carried out on the T7452-treated 7085 aluminum alloy under different temperatures (100 °C, 125 °C, 150 °C and 175 °C) for 500 h. Variations of tensile properties and hardness were exhibited. The microstructure, nano-scale precipitates and fracture characteristics of the alloy were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that with the increase of exposure temperature, the strength and hardness increase first and then decrease while the elongation and the reduction of area increase continuously as compared to those of the non-thermal exposed alloy. The transformation from η′ phase to η phase during thermal exposure occurs continuously during thermal exposure. In addition, as the exposure temperature increases, the average dimensions of precipitates and the average spacing of neighbor precipitates become larger. The influence of precipitates on mechanical properties of the alloy is discussed.
A detailed investigations of Zn/Mg ratios on stress corrosion cracking(SCC), electrochemical corrosion properties and precipitates of Al-Zn-Mg alloy with Zn+Mg ≈ 7 wt% were studied by mechanical, stress corrosion cracking(SCC), electrochemical cyclic polarization together with transmission electron microscopy (TEM) microstructural examinations. It is shown that the strength, SCC and electrochemical corrosion resistance are significantly increased with the decrease of Zn/Mg ratio. The strength of the alloys are significantly increases with the decrease of Zn/Mg ratio, which was attributed to increase the volume fraction of matrix precipitates. The enhance of SCC resistance and electrochemical corrosion properties was attributed to the narrower width of PFZ and low concentration of Zn in aluminum matrix.
High resolution transmission electron microscopy (HRTEM) with nanometer-scaled energy-dispersive X-ray (EDX) was employed to investigate the transformation mechanisms of the GP zone → η′ → η precipitation sequence of AA7050, an Al-Zn-Mg-Cu alloy. Serial in-situ HRTEM frames revealed that separated nucleation of an η′ precipitate occurred elsewhere as the adjacent GPII zone dissolved. Evidence from HRTEM coupled with EDX showed that in-situ nucleation of a new η2 precipitate (one form of η) took place, wherein it gradually developed from the original η′ precipitate via a similar hexagonal structure with different compositions. The in-situ transition product was composed of two distinctive regions; one was identified as η′, and the other, as η.
The mechanical properties, corrosion behavior, and microstructures of Al-Zn-Mg-Cu alloy during non-isothermal ageing (NIA) process were investigated. The results suggest that hardness and tensile strength generally keep improving with increasing ageing degree until the level of 182 HV and 578 MPa (cooled at 120 ℃, or C120), apart from a slight decline at the region where the temperature is beyond 200 ℃. Synchronously, the electrical conductivity increases and corrosion susceptibility decreases as the ageing proceeds. The optimal performance of the alloy is obtained at the C120 condition, whose electrical conductivity, stress corrosion susceptibility rtf and maximum corrosion depth are 40.3 %IACS, 98.2% and 24.7 μm, respectively. GPI zones and η' phases are the primary ageing precipitates at the heating stage (100–210℃, 40℃/h), then η' phases are the main ones at the cooling stage (210–100℃, 20℃/h). Reasonably, the combination of high strength and favorable corrosion resistance of the alloy through NIA treatment are associated with the growth and coarsening of intergranular precipitates during heating and newly formed fine intragranular ones during cooling.
A refined microstructure of Al-Zn-Mg-Sc-Zr alloy sheet was produced by simple hot and cold rolling to an average grain size of 3 µm. Experiments were completed in electro-fluid servo-fatigue tester and results were investigated by means of optical microscope (OM), scanning electron microscopy (SEM) and transmission electron microscope (TEM). Superplastic deformation was conducted and superplastic ductility of ≥200% was achieved at a testing temperature range from 425 ºC to 500 ºC and relative high strain rate range of 1×10⁻³ s⁻¹~1×10⁻¹ s⁻¹. The maximum elongation of 539% was obtained at 500 ºC and 1×10⁻² s⁻¹. In addition, the scanning electron microscopy (SEM) and transmission electron microscope (TEM) analyses showed that the presence of Al3 (Sc, Zr) particles in pinning grain boundaries and dislocations had a great influence on the superplastic deformation. The analyses of superplastic test data calculated out the coherent strain rates sensitivity parameter of 0.43 and the average activation energy of 143.762 kJ/mol. The data interpreted that the dominant deformation mechanism was grain boundary sliding controlled by lattice self-diffusion.
In the present work, the influence of one-step and two-step aging treatments on hardness, electrical conductivity and mechanical properties of a high Zn-containing Al-Zn-Mg-Cu alloy is investigated and detailed aging parameters subjected to various aging tempers, i.e., T6, T79, T76, T74 and T73, are proposed. The nanoscale precipitates under different tempers are qualitatively investigated by means of transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM) techniques. Based on the precipitate observations, precipitate size distributions and neighbor precipitates distances are extracted from bright-field TEM images projected along 〈110〉Al orientation with the aid of an imaging analysis. The results show that with the deepening of aging degree, the conductivity of one-step and two-step aging increase continuously while the hardness increases for one-step aging and decreases for two-step aging at the second preservation. The tensile strength decreases as the aging degree deepens and the yield strength shows a similar trend. In addition, as the degree of over-aging deepens, the precipitate size distribution interval becomes broader, the average precipitate size turns larger and the average distance of neighbor precipitates also becomes greater. The influence of precipitates on mechanical properties is discussed.
The mechanical behavior of single crystal Al sample with different sizes in mini-, micro- and nano-scales and different loading directions along [111] and [110] have been systematically investigated. The sample size and orientation effects are examined. The results are compared with previously reported data on other face-centered cubic Ni, Cu, Au and Ag, establishing an interesting trend for sample size effect with respect to stacking fault energy. With higher stacking fault energy and thus higher dislocation mobility such as Al, the sample size dependence would be lower.
The Al–Zn–Mg aluminum alloy A7N01S-T5 used in high speed trains was designed by orthogonal method. The effect of elemental composition on the tensile properties and fracture toughness has been investigated. The alloys with different compositions were tested by tensile and three point bending tests: the range analysis results showed that the compositions of Zn and Mg were the main factors that affect the strength and plasticity of the alloys. The tensile testing results showed that the #1 alloy Al-4.34Zn-1.43 Mg-0.27Mn-0.13Cr-0.12Zr-0.07Ti had the best combination of tensile strength, yield strength and elongation, which were 415 MPa, 378 MPa and 13.5%, respectively. Furthermore, this alloy showed the excellent ability to hinder the crack propagation with a value of J0.2BL(12) = 23.37 kJ·m− 2. The microstructure, grain size, compositions and fracture characteristics of the alloy were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), backscattered electron diffraction (EBSD) and transmission electron microscopy (TEM). The results indicated that the strength is mainly determined by the volume fraction, size and distribution of precipitated η′(MgZn2) phase. The discontinuous distribution of η(MgZn2) phase, narrow precipitated-free zones (PFZs) and fine grain size played important roles to obtain high fracture toughness.
A fine-grained structure of Al-Zn-Mg-Cu alloy was produced by a successive two-step deformation (STD) process based on strain-induced precipitation (SIP). The fine-grained alloy treated by the STD process exhibited significantly superior tensile ductility than the conventional hot-deformed (CHD) alloy. Effects of the STD process on microstructure and mechanical properties were investigated, in conjunction with fracture characterizations. Numerous spherical precipitates and dense dislocations were induced by the SIP at 300. °C. A fine lamellar structure was formed during subsequent heating and hot deformation of the STD process, finally contributing to the fine-grained T6-aged alloy. Due to the fine-grained structure, more dimples in the fracture surface of the STD treated alloy were produced than those of the CHD treated alloy. TEM in-situ testified that the grain boundary precipitates (GBPs) originated the initiation of micro-cracks, and the cracks propagated along the (sub)grain boundaries during the tensile loading. The initiation and propagation of micro-cracks were explained in terms of grain boundary precipitates (GBPs), precipitation free zones, and grain refinement. Although initiation and propagation of the cracks easily occur to coarse GBPs and grain boundaries, the fine-grained structure obtained by the STD treatment could effectively delay these behaviors and improve mechanical properties.
Aluminium alloys have been the primary material for the structural parts of aircraft for more than 80 years because of their well known performance, well established design methods, manufacturing and reliable inspection techniques. Nearly for a decade composites have started to be used more widely in large commercial jet airliners for the fuselage, wing as well as other structural components in place of aluminium alloys due their high specific properties, reduced weight, fatigue performance and corrosion resistance. Although the increased use of composite materials reduced the role of aluminium up to some extent, high strength aluminium alloys remain important in airframe construction. Aluminium is a relatively low cost, light weight metal that can be heat treated and loaded to relatively high level of stresses, and it is one of the most easily produced of the high performance materials, which results in lower manufacturing and maintenance costs. There have been important recent advances in aluminium aircraft alloys that can effectively compete with modern composite materials. This study covers latest developments in enhanced mechanical properties of aluminium alloys, and high performance joining techniques. The mechanical properties on newly developed 2000, 7000 series aluminium alloys and new generation Al-Li alloys are compared with the traditional aluminium alloys. The advantages and disadvantages of the joining methods, laser beam welding and friction stir welding, are also discussed.
Fine-scale precipitation of the metastable Zn- and Mg-rich η′ phase and its precursors is essential for the mechanical properties of Al–Zn–Mg alloys. However, at present neither the precipitation sequence nor the structure and composition of the intermediate precipitate phases are completely clear. This paper deals with an investigation of precipitation in an industrial Al–Zn–Mg alloy at various stages of a conventional two-step ageing treatment at 100° and 150°C. Studies were performed using both transmission electron microscopy and atom-probe field ion microscopy. Transmission electron microscopy (TEM) analysis revealed two parallel precipitation paths; one involving formation and dissolution of the ordered GP (I) zones, the other involving formation of clusters (type II), having a different atomic arrangement compared to the Al-matrix, which transform to the η′ phase. Atom-probe study of the material after short time ageing at 100°C did not show any observable distinction between GP (I) and type II precipitates. In the peak-aged material the best classification of precipitates was obtained using their morphology (the cigar-like and the plate-like) because there was significant overlap in the range of total solute contents of each type of precipitate. Generally the Zn:Mg ratio in all observed types of precipitates was close to 1:1 and the total solute atom content increased with ageing time. Distribution of alloying elements in the precipitates and in the surrounding matrix is discussed.
To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precip-itation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are 102 MPa) and in the T6-tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively.
A bulk nanostructured alloy with the nominal composition Cu–30Zn–0.8Al wt.% (commercial designation brass 260) was fabricated by cryomilling of brass powders and subsequent spark plasma sintering (SPS) of the cryomilled powders, yielding a compressive yield strength of 950 MPa, which is significantly higher than the yield strength of commercial brass 260 alloys (∼200–400 MPa). Transmission electron microscopy investigations revealed that cryomilling results in an average grain diameter of 26 nm and a high density of deformation twins. Nearly fully dense bulk samples were obtained after SPS of cryomilled powders, with average grain diameter 110 nm. After SPS, 10 vol.% of twins is retained with average twin thickness 30 nm. Three-dimensional atom-probe tomography studies demonstrate that the distribution of Al is highly inhomogeneous in the sintered bulk samples, and Al-containing precipitates including Al(Cu,Zn)–O–N, Al–O–N and Al–N are distributed in the matrix. The precipitates have an average diameter of 1.7 nm and a volume fraction of 0.39%. Quantitative calculations were performed for different strengthening contributions in the sintered bulk samples, including grain boundary, twin boundary, precipitate, dislocation and solid-solution strengthening. Results from the analyses demonstrate that precipitate and grain boundary strengthening are the dominant strengthening mechanisms, and the calculated overall yield strength is in reasonable agreement with the experimentally determined compressive yield strength.
This paper investigates the effect of alloying elements on the characteristics of intermetallic phases in Zr-containing and Cr-containing 7xxx Al–Zn–Mg–Cu alloys at overaged conditions. Four Al–Zn–Mg–Cu alloy plates with different alloying element contents were studied by optical microscopy based image analysis, differential scanning calorimetry, scanning electron microscopy combined with energy disperse X-ray spectroscopy and transmission electron microscopy. The grain structures, recrystallisation, intermetallic phases and precipitates in the selected alloys have been analyzed and the presence of coarse intermetallic phases has been interpreted using established phase diagrams. The different effects of Zr or Cr addition to the alloys have been compared. The experimental results showed that the recrystallised area fraction of Zr-containing alloys is less than that of Cr-containing alloys, being attributable to Zr reducing recrystallisation more effectively than Cr. The detected particles are mainly S phase, Al7Cu2Fe, as well as dispersoids of Al3Zr for Zr-containing alloys and Cr-rich E phase for Cr-containing alloys. These coarse particles, especially the S phase which cannot be dissolved during solution treatment, are detrimental to the fracture toughness of the alloys.
The design of an aluminum alloy having good strength while maintaining a high resistance to fracture is discussed. Theory suggests that the desired microstructure consists of a small volume fraction of an ultra-fine dispersion of hard particles. In addition to conventional heat treatments, dispersion hardened aluminum alloys have been recently produced by rapid solidification or mechanically alloying and powder metallurgy consolidation. Alloys which can serve as models for mechanistic studies of nucleation of non-coherent phases as well as the basis for a new class of engineering aluminum alloys are identified.
Solution and quench treatments are very important for the heat-treatable aluminum alloys because any change in these treatments will induce a trade-off in volume fraction between the constituents and precipitates and so will cause a change in the mechanical properties. In this paper, three types of solution + quench treatments were applied to two kinds of aluminum alloys, i.e., the Al–Cu–Mg alloy that contains disc/plate-shaped precipitates and the Al–Mg–Si alloy that contains rod/needle-shaped precipitates, to change the relative content between the constituents and the precipitates and to develop different coupling of the constituent and precipitates. The specimen treated with an enhanced solution or a stepped solution is found to exhibit a significant increase in yield strength, ductility, and fracture toughness. A multiscale model is presented to quantitatively estimate the coupled influence of the constituents and precipitates on the mechanical properties by combining with a strengthening model. The experimentally observed non-monotonic dependence of ductility on the trade-off in volume fraction between the constituents and precipitates is reasonably explained by using this multiscale model. In addition, the influence of stress triaxiality level on the ductility and fracture toughness is also calculated. All the calculations are in quite good agreement with the experimental results.
The structure of the η′ phase, one of the most important age-hardening precipitates in commercial Al–Zn–Mg alloys, has been studied at the atomic level by means of high-resolution electron microscopy (HREM). A structural model of the η′ phase has been constructed on the basis of the structural characteristics in the observed images and the structure of the η-MgZn2 phase. Image simulation of this model shows a good agreement between calculated and experimental images. Comparison of this model with the early existing model on the basis of the X-ray diffraction is also given.
Aluminum alloys have been the primary material of choice for structural components of aircraft since about 1930. Although polymer matrix composites are being used extensively in high-performance military aircraft and are being specified for some applications in modern commercial aircraft, aluminum alloys are the overwhelming choice for the fuselage, wing, and supporting structure of commercial airliners and military cargo and transport. Well known performance characteristics, known fabrication costs, design experience, and established manufacturing methods and facilities, are just a few of the reasons for the continued confidence in aluminum alloys that will ensure their use in significant quantities for the rest of this century and likely well into the next one. But most significantly, there have been major advances in aluminum aircraft alloys that continue to keep them in a competitive position. In the early years aluminum alloys were developed by trial and error, but over the past thirty years there have been significant advances in our understanding of the relationships among composition, processing, microstructural characteristics and properties. This knowledge base has led to improvements in properties that are important to aircraft applications. This review covers the performance and property requirements for airframe components in current aircraft and describes aluminum alloys and product forms which meet these requirements. It also discusses the structure/property relationships of aluminum aircraft alloys and describes the background and drivers for the development of modern aluminum alloys to improve performance. Finally, technologies under development for future aircraft are discussed.
The composition and volume fraction of nanometre size precipitates has been characterised in an Al–Zn–Mg alloy (AA7108.50) in two states of ageing, namely the T6 state, containing mostly metastable η′ precipitates, 2.5 nm in radius, and the T7 state, containing mostly stable η precipitates, 4 nm in radius. Three complementary experimental techniques have been used in order to provide for the first time two independent measurements of the precipitate composition and volume fraction: tomographic atom probe, small-angle X-ray scattering, and transmission electron microscopy. The composition of precipitates in the T7 state are shown to be very close to the equilibrium MgZn2 composition, with an aluminium content smaller than 10%. In the case of the T6 material, the most probable composition is proposed as 55% Zn, 25% Mg and 20% Al.
The structure of GP-zones in an industrial, 7xxx-series Al–Zn–Mg alloy has been investigated by transmission electron microscopy methods: selected area diffraction, conventional and high-resolution imaging. Two types of GP-zones, GP(I) and (II) are characterized by their electron diffraction patterns. GP(I)-zones are formed over a wide temperature range, from room temperature to 140–150°C, independently of quenching temperature. The GP(I)-zones are coherent with the aluminum matrix, with internal ordering of Zn and Al/Mg on the matrix lattice, suggested to be based on AuCu(I)-type sub-unit, and anti-phase boundaries. GP(II) are formed after quenching from temperatures above 450°C, by aging at temperatures above 70°C. The GP(II)-zones are described as zinc-rich layers on {111}-planes, with internal order in the form of elongated <110> domains. The structural relation to the η′-precipitate is discussed.
The 7XXX series age-hardenable high-strength aluminum alloys find useful applications in the field of aerospace engineering. Constant efforts are being made to tailor the mechanical and corrosion properties of these alloys as per requirements for a particular application. These properties are a function of factors like microstructure, chemical composition and processing parameters. An effort has been made to collate the information available from different studies conducted on alloys Al 7050 and Al 7055. Databases were created to consolidate the information about microstructure, mechanical properties and corrosion behavior for the two alloys. Existing models were utilized to predict strength and fracture toughness for these alloys and these models were validated using experimental values and a qualitative evaluation was made for the corrosion behavior of these alloys. Available data were utilized to prepare maps that are intended to serve as guides to design aluminum alloys with desired combination of properties.
Process modelling techniques are used to describe the changes in yield strength due to age hardening of heat-treatable aluminium alloys. A model for the isothermal ageing curve is developed. This is demonstrated for a number of alloys and the success of the approach is assessed. Applications and a new diagram, showing the variation of strength with temperature and time, are described in an accompanying paper.RésuméOn utilise les techniques de la modélisation pour décrire les modifications de la limite élastique causées par le vieillissement dans des alliages d'aluminium sensibles au traitement thermique. On développe un modèle de la courbe du vieillissement isotherme. On démontre la validité et le succès de ce modéle dans le cas de plusieurs alliages. Dans l'article suivant, on décrit les applications du modèle et un nouveau diagramme montrant la variation de la résistance mécanique en fonction de la température et du temps.ZusammenfassungDie durch Auslagerungshärtung entstehenden Änderungen in der Flieβfestigkeit von wärmebehandlungsfähigen Aluminiumlegierungen werden mittels Verfahren der Prozeβmodellierung beschrieben. Es wird ein Modell für die isotherme Alterungskurve entwickelt. Dieses Modell wird an einer Reihe von Legierungen veranschaulicht; der Wert dieser Näherung wird dargelegt. Anwendungen und ein neues Diagramm, welches die Änderungen der Festigkeit mit der Temperatur und der Zeit darstellen, werden in einer begleitenden Arbeit beschrieben.
The effect of ageing times and temperatures up to 200°C on the characteristics of serrated flow in an Al–Zn–Mg–Cu alloy was investigated. Tests at room temperature were conducted on a hard tensile machine. Experimental measurements of the serrated yielding show the important influence of precipitation. In particular, Guinier–Preston (GP) zones reduce the tendency to serrated flow and increase the onset strain of serrations, εc. Precipitates formed at high ageing temperatures favour the occurrence of serrated flow. However, the εc values remain higher than those observed for materials aged at very low temperature. The influence of precipitation of the magnitude of the stress drop has also been examined.
Yield strength at ambient temperature and creep resistance between 225 and 300°C were investigated in dilute Al(Sc) alloys containing coherent Al3Sc precipitates, which were grown by heat-treatments to radii in the range 1.4–9.6 nm. The dependence of the ambient-temperature yield stress on precipitate size is explained using classical precipitation strengthening theory, which predicts a transition from precipitate shearing to Orowan dislocation looping mechanisms at a precipitate radius of 2.1 nm, in good agreement with experimental data. At 300°C creep threshold stresses are observed and found to be much lower than the yield stresses, indicative of a climb-controlled bypass mechanism. The threshold stress increases with increasing precipitate radius, in qualitative agreement with a climb model taking into account stiffness and lattice mismatches between matrix and precipitates [1].
An attempt is made here to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grain-boundary theory. On this hypothesis, a satisfactory explanation of the variation of the lower yield point with grain size may be developed. It is shown that strain-ageing must involve two processes: a healing of the grain-boundary films, coupled with a hardening in the grains themselves. A discussion of the possible nature of the grain-boundary film is also undertaken.
The second edition of this textbook, popular amongst students and faculty alike, investigates the various causes of thermodynamic instability in metallic microstructures. Materials theoretically well designed for a particular application may prove inefficient or even useless unless stable under normal working conditions. The authors examine current experimental and theoretical understanding of the kinetics behind structural change in metals. The entire text has been updated in this new edition, and a completely new chapter on highly metastable alloys has been added. The degree to which kinetic stability of the material outweighs its thermodynamic instability is very important, and dictates the useful working life of the material. If the structure is initially produced to an optimum, such changes will degrade the properties of the material. This comprehensive and well-illustrated text, accompanied by ample references, will allow final year undergraduates, graduate students and research workers to investigate in detail the stability of microstructure in metallic systems.
Fine precipitation scenarios of AlZnMg(Cu) alloys revealed by advanced atomic-resolution electron microscopy study Part I: structure determination of the precipitates in AlZnMg(Cu) alloys
- Liu
A review of: “DISPERSION STRENGTHENED ALUMINUM ALLOYS”
- Srivatsan