Article

Effect of large cold deformation on characteristics of age-strengthening of 2024 aluminum alloys

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Abstract

Effect of large cold deformation on the age-hardening characteristics of 2024 aluminum alloys was investigated. The results reveal: 1) the aging response is accelerated after large cold deformation, and the peak strength is attained after aging for 40 min; 2) double aging peaks can be found in the age-hardening curves, and the first peak appears when aged for 40 min. The corresponding peak tensile strength (σb) and elongation are up to 580 MPa and 9.2% respectively, the second peak appears when aged for 120 min, but the peak tensile strength (520 MPa) is lower than the first one; 3) in early stage of aging (

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... It is postulated that with the use of a thermomechanical processing route, that combines deformation with the aging process, superior mechanical characteristics can be attained. For example, a double peak aging strengthening was achieved by the application of deformation in the thermal treatment of AA2024 aluminum alloy [8]. ...
... This means that the effect of deformation-induced precipitates would be far more superior to the normal aging precipitation. A double peaks characteristics was found in the strengthening of 2024 aluminum alloy via the application of cold deformation which was related to the acceleration of GP zones formation through higher dislocation density [8]. ...
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In this investigation, the effect of the amount of cold rolling on the single stage and double stage aging responses of an AA2024 aluminum alloy was assessed. Two cold deformation amounts were applied on the solution heat treated AA2024 sheets. The effect of these deformation on a two-step short time aging performed at low, and subsequently at high temperatures, were studied in terms of precipitation and mechanical properties variations. As well, the effect of rolling percentage on the singe stage of overaging was assessed. Microstructural evolution was studied by optical microscope (OM) and Field Emission Scanning Electron Microscope (FE-SEM) and Transmission Electron Microscope (TEM). Mechanical properties were assessed through tensile testing and microhardness variation. Electrical conductivity (EC) measurements were also made to track the changes of precipitation condition. Results showed that applying cold rolling substantially increased the strength and slightly reduced ductility. In addition, performing the cold rolling created better condition, through dislocation generation, for the strengthening precipitates. Under such a condition, a short time aging through double aging process provided higher strength level compared with the long aging process of the overaging treatment. TEM studies showed the development of sub-structure through dislocation cells formation for the cold deformed cases. It also showed that very small size S′ hardening precipitates are present for the highest level of strength/hardness achieved in the double aging process. Also TEM studies suggested that no morphological changes occurred in the highest strength level achieved for the double aged conditions. Microhardness and electrical conductivity variation followed the same trend as the strength variation, for both the double aging process and the overaging condition.
... It is worth highlighting that the coexistence of h'' and h' phases have been reported in an aluminum alloy without Mg content [38]. However, although the activation energy for Mg diffusion in aluminum is lower than the Cu diffusion [32], the high density of dislocations can act as atomic diffusion paths in the deformed alloy, which accelerates the aging process by promoting the formation of GPB zones or phase transformations of h' and S' [39]. The above behavior could also be related to the lower Cu atomic size facilitating its segregation in a distorted aluminum lattice, favoring the formation of the h' phase. ...
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The present study aims to evaluate plastic deformation's effect by cold-rolling on the precipitation sequence of 2024 aluminum alloy. X-ray diffraction, scanning/transmission electron microscopy, and Vickers microhardness tests have been used to characterize the microstructure and mechanical behavior of the alloys. It was observed that plastic deformation induces changes in the precipitation sequence, which affects the mechanical properties and delays the overaging stage. In the deformed alloy, two hardening peaks were observed. These peaks occurred at 30 min (248 HV ± 5) and 600 min (230 HV ± 2) and were attributed to the θ' and S' phases, respectively. However, in the non-deformed alloy, only a single hardening peak was observed. This peak arose after 300 min aging (208 HV ± 4) and was attributed to the S' phase formation. Thus, the precipitation sequence in the deformed alloy was the following: αSSS–CuMg clusters → GPB-II zones/θ''/θ'/ → S' → S, and for the non-deformed alloy was αSSS–CuMg clusters → GPB-II zones/S'/ → S. Graphical abstract
... The cold plastic deformation of the alloy from the metastable condition of metallurgical microstructure increases the dislocation density, which favors the atomic diffusion of solute atoms. It also elevates the response to treatment of aging, resulting in an intense effect in increasing alloy strength [12][13][14] . ...
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Brazilian aeronautical industries report that, due to the high mechanical properties presented commercially, AA2024-T351 alloy presents fissures and non-homogeneous deformations during the mechanical processing. This work proposes a manufacturing process capable of increasing the ductility of the material to withstand tensions during processing and a subsequent treatment to recover the mechanical strength of the alloy. The sequence of operations begins with the super-heat treatment at 415ºC 2.5 h, solubilization at 495ºC 2.0 h, mechanical conformation with a degree of area reduction from10% to 90% and artificial aging at 190ºC at times of 2, 4, 6 and 8 hours. The results allowed to obtain an operational sequence where it is possible to form the alloy in the desired component, without loss of mechanical properties and structural defects, in the shortest time possible of heat treatment, reducing the manufacturing costs and increasing productivity.
... QUAN et al [9] indicated that the pre-deformation can increase the strength and reduce the time to reach the peak hardness of 2524 Al alloy. NING et al [10] studied the effect of cold deformation on characteristics of 2024 Al alloy and found that a characteristic of double peaks aging strengthening phenomenon appears. A high density of dislocation introduced by cold deformation accelerates the precipitation of GP zones and aging response of the alloy. ...
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The effects of pre-deformation following solution treatment on the microstructure and mechanical properties of aged high purity Al–Cu–Mg alloy were studied by tensile test, micro-hardness measurements, transmission electron microscopy and scanning electron microscopy. The micro-hardness measurements indicate that compared with un-deformed samples, the peak hardness is increased and the time to reach peak hardness is reduced with increasing pre-strain. Additionally, a double-peak hardness evolution behavior of cold-rolled (CR) samples was observed during aging. The results of TEM observation show that the number density of S′(Al2CuMg) phase is increased and the size is decreased in CR alloy with increase of pre-strain. The peak hardness and peak strength of the CR alloy are increased because of quantity increasing and refinement of S′ phase and high density dislocation.
... The presence of precipitate nuclei, which are generated during the deformation process, increases the aging rate and shifts the hardening peak to shorter times [6,21]. When the aging time increases and the nucleation and growth process continue, these processes increase the number density of precipitates and lead to the second hardening peak in the aging curve [5,6,21]. The HV hardness values obtained show a double hardening peak, which is not observed in Fig. 3 corresponding to the HRB hardness values. ...
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This paper reports changes in the hardness values and precipitation of the Al2024 alloy when it is modified with Zn addition (0.25, 0.50 and 0.75 wt. %) and plastic deformation (hot-50% and cold-5 and 15%). It is reported increases in the hardness values by Zn addition. Furthermore, a double hardening peak with bimodal distribution of precipitates associated with the continuous process of nucleation and growth of the S and S′ phases is observed.
... By applying a thermomechanical processing route, that combines deformation with the aging process, superior mechanical characteristics can be attained. The effect of cold rolling of commercial grade AA2024 with a deformation between 50 and 65% together with a short-term low-temperature ageing [19] showed an increase in the dislocations density and promoted the formation of rod-shaped Guinier-Preston zones, resulting in the distortion of the matrix lattice. ...
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This study has been conducted to investigate the effects of plastic deformation of an AA2024 aluminium alloy by cold rolling to 25%, 50% and 75% and then heat-treating and naturally ageing for 20 days to T4 on the microstructure and the electrochemical behavior. To characterize the microstructural modifications different techniques have been applied such as X-ray Diffraction (XRD) to demonstrate the intermetallic phases formed, Optical Microscopy (OM) and Scanning Electronic Microscopy (SEM) to evaluate their microstructures and grain size. Moreover, the surface topography has been measured to establish the roughness effect on the mechanical response when subjected to tensile, fatigue and micro-indentation tests. The corrosion behaviour was evaluated by Potentiodynamic Polarization Scanning, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The results revealed that cold-rolled samples with 50% plastic deformation show a smoother topography and exhibit the best compromise between mechanical and corrosion resistance.
... In conclusion, the thermal input and the accumulation of plastic deformation caused a deterioration in mechanical properties after the FSW treatment. There was a dramatic decrease in the ductility of the 2219 aluminum alloy under the co-effect of FSW and heat treatment as a result of the interaction between severe plastic deformation and aging [27]. Through a comparison of the tensile results which were processed under all the four technologies above, it was clear that the strength loss due to the FSW process could be largely recovered by the solution aging treatment, which was mainly attributable to the high temperature during solution treatment. ...
Article
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Among available processing technologies of heat-treatable aluminum alloys such as the 2219 aluminum alloy, the use of both friction stir welding (FSW) as joining technology and electromagnetic forming (EMF) for plastic formation technology have obvious advantages and successful applications. Therefore, significant potential exists for these processing technologies, both of which can be used on the 2219 aluminum alloy, to manufacture large-scale, thin-wall parts in the astronautic industry. The microstructure and mechanical properties of 2219 aluminum alloy under a process which compounded FSW, heat treatment, and EMF were investigated by means of a tensile test as well as via both an optical microscope (OM) and scanning electron microscope (SEM). The results show that the reduction of strength, which was caused during the FSW process, can be recovered effectively. This can be accomplished by a post-welding heat treatment composed of solid solution and aging. However, ductility was still reduced after heat treatment. Under the processing technology composed of FSW, heat treatment, and EMF, the forming limit of the 2219 aluminum alloy decreased distinctly due to the poor ductility of the welding joint. A ribbon pattern was found on the fractured surface of welded 2219 aluminum alloy after EMF treatment, which was formed due to the banded structure caused by the FSW process. Because of the effects of induced eddy current in the EMF process, the material fractured, forming a unique structure which manifested as a molten surface appearance under SEM observation.
... In conclusion, the welding defects and the accumulation of plastic deformation would cause a 178 deterioration in mechanical properties after the FSW treatment. There will be a dramatic decrease in 179 the ductility of 2219 aluminum alloy under the co-effect of FSW and heat treatment due to the 180 interaction between severe plastic deformation and aging [23]. By comparing the tensile results which ...
Preprint
Among all the processing technologies of heat-treatable aluminum alloys like 2219 aluminum alloy, using friction stir welding (FSW) as the joining technology and using electromagnetic forming (EMF) for plastic forming technology both have obvious advantages and successful applications. Therefore, there is a broad prospect for the compound technologies which can be used on the 2219 aluminum alloy to manufacture the large-scale thin-wall parts in the astronautic industry. The microstructure and mechanical properties of 2219 aluminum alloy under the process compounded of FSW, heat treatment, and EMF were investigated by means of tensile test, optical microscope (OM), and scanning electron microscope (SEM). The results show that the reduction of strength, which was caused during the FSW process, can be recovered effectively by the post-welding heat treatment composed of solid solution and aging, while the ductility was still reduced after heat treatment. Under the compound technology of FSW, heat treatment, and EMF, the forming limit of 2219 aluminum alloy decreased distinctly due to the poor ductility of the welding joint. A ribbon-pattern, which was formed due to the banded structure caused by FSW process, was found on the fracture surface of welded 2219 aluminum alloy after EMF treatment. During the EMF process, because of the effects of induced eddy current, a unique structure, which was manifested as a molted-surface appearance under the SEM observation, was formed as the material fractured.
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div class="title">Effect Mg Addition on Microstructure and Hardness of AI2024 Alloy after Thermo-Mechanical Treatments - Volume 22 Issue S3 - C.G. Garay-Reyes, I. K Gómez-Barraza, M. A. Ruiz-Esparza-Rodríguez, E. Cuadros-Lugo, H. M. Medrano-Prieto, I. Estrada-Guel, M. C. Maldonado-Orozco, R. Martínez-Sánchez
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The effect of thermomechanical treatment (TMT) on the structures, precipitation behaviour, and mechanical properties of commercial-grade aluminium 2036 alloy has been investigated. In both the solutiontreated and aged and the TM-treated conditions, the main strengthening phase was observed to be ?? Prestraining of the material accelerates the precipitation of ??-phase and reduces the ageing time required to achieve maximum strength. By raising the temperature of deformation, the distribution of dislocations changes from cellular to uniform and also causes a finer and more uniform distribution of ??-precipitates. The combined effect of uniform dislocation and ??-precipitate distribution results in increased strength without any significant loss in ductility.
Article
AlMg5 and AlCu4Zr alloys have been deformed in the range of true deformations ϕ=0.4–13.9 using the cyclic extrusion compression (CEC) method. In the entire range of the examined deformations a strong tendency to form microbands in the dislocation structure of the alloys has been observed. In the area of the microbands a strong misorientation of 60° occurred. Characteristic changes appearing as a result of the intersection of the microbands, leading to the formation of subgrain microstructure, have been observed. Similarly as in the microbands, large misorientation angles between the newly formed subgrains occurred. The nanometric dimensions of the newly formed subgrains and large misorientations angles in the alloys, plastically deformed above the conventional deformation range, indicated the tendency to form a microstructure typical for metallic nanomaterials.
Article
Substructure strengthening has been utilized by the wire industry to produce high strength, high conductivity, ductile aluminum wire suitable for electrical usage. This paper describes the choice of alloy additions and production methods necessary for producing and stabilizing a small subgrain structure. The interrelation between the various manufacturing steps, such as casting, rolling, and drawing, and the resulting microstructure which controls the electrical and mechanical properties is discussed. The necessity for strict control of the processing parameters established for various aluminum wire products is emphasized.
Article
High-purity Al-Zn-Mg alloy was thermomechanically treated. The process included solution treatment, pre-ageing, cold-working by rolling and final ageing. Pre-ageing was carried out at 100C (TAHA1) and room temperature (TAHA2). Experimental results indicated that the TAHA1 process improved the tensile strength significantly while the TAHA2 process improved the fatigue life more substantially. Fatigue crack initiation sites were examined carefully by scanning electron microscopy. A correlation between fatigue crack initiation, fatigue striation, tearing ridge, dimple distribution and fatigue life was observed. The experimental results are discussed in terms of substructure and are also compared with the tensile and fatigue properties of a thermomechanically treated 7075 Al-Zn-Mg alloy which were previously reported by one of the authors.
Article
The influence of SiC particulate size on the age-hardening response of 2009 aluminium has been monitored utilizing hardness, electrical conductivity and differential scanning calorimetry. Ageing involved either two or three stages depending on the reinforcement size. For 2009 Al reinforced with 29 μm SiCp, initial ageing consisted of GPB (Guinier Preston Baqaryatsky) I zone formation. Decreasing the particulate size to 4 μm eliminated GPB I formation. This suppression of GPB I formation during ageing suggests that decreasing SiC size decreases the vacancy supersaturation following quenching by providing additional vacancy sinks at SiC/matrix interfaces. Subsequent ageing involved, at the larger reinforcement sizes, a transition with increasing time from GPB I zones to GPB II-dislocation complexes. At smaller (4 μm) reinforcement sizes, the formation of GPB II-dislocation complexes occurs directly. Finally, the last stages of age hardening in all SiCp-reinforced composites examined consisted of heterogeneous nucleation of S′/S and GPB II→S′/S transformation.
Article
The technological process used for the production and processing of metal matrix composites (MMCs) can require contact over extended periods of time between matrix and the ceramic reinforcement or at least the permanence at high temperature and pressure of the two parts in contact. During the contact a chemical interaction takes place in the interfacial zone as a consequence of the free-energy difference existing between ceramic compound and metal. Aluminium and aluminium alloys reinforced with silicon carbide are widely utilized materials. The chemical interaction between matrix and reinforcement is not very fast but the reaction equally occurs, and a harmful layer of interfacial compound (Al4C3) is developed after a sufficiently long time. At present, the degradation of the reinforcement produced by molten matrix is the major problem for some production technologies. This problem has only been solved partially by using a coating or changing the chemical nature of the matrix. In particular, the technological problem of interfacial reaction in the SiC-Al system can be solved by adding elemental silicon to the matrix to achieve the eutectic composition. However, this expedient gives rise to a consequent significant lowering of the melting point. The problem can be overcome and the production process improved without changing the characteristics of the material by the control of processing parameters. The interfacial reaction also produces elementary silicon and this has been found as aluminium-silicon eutectic segregated at the aluminium grain boundary. An accurate description of the kinetic process can be obtained by determining the silicon content present in the matrix by original derivations obtained by means of calorimetric analysis.
Article
Thermomechanical treatment has been used as an important process for improving the structure and properties of materials, simplifying production techniques and saving energy resources. At present thermomechanical treatment is widely used in the manufacture of products of steel and ageing alloys, and has given valuable research results. Research on the influence of thermomechanical treatment on the tensile and notch toughness properties and stresscorrosion performance of AI-Mg-Si alloy have been reported by several researchers [1,2]. However, the published literature concerning the dimensional stability of aluminium alloy is relatively sparse. Dimensional stability has been one of the important problems facing those who design and use heat-treated aluminium alloys. Three factors control the dimensional stability of an aluminium part. These are the change in temperature during the thermomechanical treatment, the microstructural changes that occur during thermal or mechanical processing of the part, and the residual stresses imparted to the part by various processing operations. Thermomechanical treatment is a type of heat-treatment including plastic deformation, which increases the density of defects and thus affects the formation of the structure in the phase transformations occurring during thermal action. Through the use of thermomechanical treatment, aluminium alloys have been increased in strength but need to undergo rational stabilization to have a stabilized structure and reduced residual stress. Finally, the purpose of stabilizing the dimensions is obtained. The purpose of this investigation was to study the changes in the structure and properties of LD2 aluminium alloy with solution heat-treatment, cold deformation, artificial ageing and stabilization during thermomechanical treatment. A set of technical standards is presented which can meet the need for high strength and dimensional stability in LD2 aluminium alloy. The material used in this experiment was LD2 forged aluminium rod with a diameter of 100 mm. The chemical composition of this alloy is given in Table I. The rod was forged to a 60mm
Article
To decrease the accumulation of damage during long-life low-stress cyclic loading, microstructures must accommodate inelastic deformation by homogeneous or “dispersed” slip rather than by localized slip concentrations. In age-hardening aluminum alloys this requirement can be met by introducing a dense and uniform dislocation forest through suitable thermo-mechanical treatments. Such a treatment was developed for Al-Zn-Mg-Cu (7075) alloys, involving a process cycle of solution annealing, partial aging, mechanical working and final aging. The fatigue properties (S-N curves) of commercial and high-purity 7075TMT are compared with conventional 7075-T651 properties; with zero mean stress the alternating stress to cause failure in 107 cycles is more than 25 pct higher for commercial-purity 7075TMT and almost 50 pct higher for high-purity 7075TMT. The results emphasize the importance of microstructural control when high fatigue resistance is required.
Article
Previous investigations of phase equilibria in the ternary system Al-C-Si have shown that silicon carbide is attacked by pure aluminium at temperatures higher or equal to 9233 K and up to about 1600 K, according to the chemical reaction: 4Al+3SiC Al4C3+3Si In the present work, a study has been carried out to obtain more detailed information on the mechanism and kinetics of this reaction. For that purpose, 6H silicon carbide platelets with broad Si (0 0 0 1) and C (0 0 0 1) faces were isothermally heated at 1000 K in a large excess of liquid aluminium. Characterization of the resulting samples by Auger electron spectroscopy (AES) and scanning electron microscopy (SEM) revealed that the reaction proceeds in both faces via a dissolution-precipitation mechanism. However, the polarity of the substrate surface strikingly influences the rate at which silicon carbide decomposes: dissolution starts much more rapidly on the Si face than on the C face, but, while a barrier layer of aluminium carbide is formed on the Si face protecting it against further attack, the major part of the C face remains directly exposed to liquid aluminium and thus may continue to dissolve at a low but constant rate up to complete decomposition of the -SiC crystal.
Article
An investigation was carried out to determine the metallurgical properties of Al-Zn-Mg and Al-Zn-Mg-Cu alloy products processed according to newly developed Final Thermomechanical Treatments (FTMT) of T-AHA type. The results show that these cycles can be utilized to produce wrought products of high purity Al-Zn-Mg(-Cu) alloys characterized by equivalent toughness and ductility and much higher strength than conventionally processed commercial purity materials. Based on transmission electron microscopy studies, it was found that such improved behavior of FTMT material is attributable to the superposition of hardening effects, from aging precipitation and from dislocations. Preliminary stress-corrosion and fatigue tests indicate that these properties are not substantially influenced by T-AHA thermomechanical process. Further work is needed in this area, in order to better understand the directions to follow for developing better alloys.
Article
2014 aluminium alloy was subjected to various thermomechanical ageing (TMA) treatments which included partial peak ageing (25% and 50%), warm rolling (10% and 20%) and further ageing to peak hardness level at 160 C. The tensile tests reveal that TMA treatments cause a substantial improvement in tensile properties and thermal stability. The electron microscopic studies reveal that the TMA treatments affect substantially the ageing characteristics. The TMA Ib treatment yields the finest needles having longitudinal dimensions of 40nm. The TMA treatments also lead to precipitate-dislocation networks of different densities. It is observed that TMA IIb treatment results in the densest precipitate-dislocation tangles of all the TMA treatments. As a result, a significant improvement in the tensile properties of 2014 aluminium alloy has been observed.
Article
The effects of deformation temperature, the amount of strain at this temperature, and the subsequent aging temperature on the precipitation hardening behavior of a high-purity 6061 aluminum alloy have been examined. The influences of prior strain are minimal if, after deforming at 298 K, aging is carried out within a temperature regime where zone formation predominates, e.g., 348 K. In contrast, if aging is performed at higher temperatures, e.g., 398 K and 448 K, pre-strain actually enhances the nucleation and early growth stages of semi-coherent intermediate phase precipitation. While variations in the amount of deformation at low temperature, i.e., 298 K, do not appear to influence the subsequent aging response, increases in the deformation temperature, e.g., to 448 K, can be quite detrimental. These results are shown to be consistent with our present knowledge of the factors controlling the steady state nucleation rate of intermediate phase precipitates. It appears that the most important effect of prior deformation lies in its ability to increase this nucleation rate by decreasing the volume strain energy change contribution to the Gibbs free energy necessary for the formation of a critical nucleus.
Article
A thermo-mechanical processing technique for reducing the transverse effect of high strength Al alloys is described. The technique, called Intermediate Thermo-Mechanical Treatment (ITMT) was applied to a high purity AlZnMgCu, 7075 type alloy.ITMT is based on the combination of warm deformation and heat treatments, and involves the recrystallization of the ingot in small equiaxed grains, in an intermediate stage of the working.As a result of the present processing, the alloy exhibits better ductility, toughness and stress corrosion properties, for a given strength, than have conventionally processed materials, mainly in the transverse directions.Moreover, it has been found that the combination of ITMT and FTMT (Final Thermo-Mechanical Treatment) results in wrought products characterized by exceptionally high properties.
Article
An investigation was conducted on the structures and properties of aluminum-based alloys 7050 and 2224 with submicrocrystalline grains produced by severe plastic deformation through equal-channel angular pressing (ECA pressing). Special attention was paid to how the heat treatments before or after ECA pressing affected the structures and properties of alloys 7050 and 2224. The results showed that the ultimate tensile strength (UTS) of alloy 7050 reached 677 MPa, with elongation to failure of 15%, while the UTS of alloy 2224 reached 618 MPa, with elongation to failure of 12%. The forming of finer grains after ECA pressing resulted from cutting off shearing bands directly and from recrystallization at certain strain and annealing regimes. In this paper, three strengthening mechanisms were considered: grain refinement strengthening, high dislocation strengthening, and more homogenous and finer precipitations than the conventional T6-treated alloy.
Article
The aging behaviour of AA2024/0, 8, 14, 19, and 24 vol.% SiCp composites was studied using the hardness Rockwell B and X-ray diffraction techniques. The composites were manufactured by stir-casting in the semi-solid state of the alloy AA2024 (compocasting). Aging of the composites and unreinforced alloy took place at 177 °C for a period of 2–200 h. Precipitation phases present were Al2CuMg for the unreinforced alloy 2024, and CuAl2, Mg2Si for the composites. Peak hardness increased as the SiCp volume fraction increased and appeared almost at the same time after about 14 h aging in all the materials. The hardness reduction rate in the overaged condition decreased with increasing SiCp content.
Article
The influence of changes in chemical composition and pre-aging deformation on the resistance to stress corrosion cracking in the age-hardenable aluminum alloy 2519 was investigated by transmission electron microscopy. The improvement of this resistance may be accomplished by keeping the Cu concentration on the lower side of the allowed limit for the 2519 alloy. Also, plastic deformation prior to aging, comprising both cold rolling and stretching, seems to be beneficial since it promotes a more homogeneous distribution of the precipitates and reduces the number of precipitates on the grain boundaries and thus shrinks the total volume of precipitation-free zones at grain and subgrain boundaries.
Article
Studies suggest donor age and year of transplantation are associated with low graft survival in liver transplant recipients with hepatitis C. We sought to determine if advanced donor age and recent year of transplantation are associated with graft survival in hepatitis C recipients and to determine if the effect of donor age on graft survival is specific to hepatitis C. We analyzed the United Network for Organ Sharing liver transplant database from 1994 to 2002. Six thousand four hundred and four subjects transplanted for end-stage liver disease from chronic hepatitis C met our criteria. One-year graft survival in hepatitis C recipients with organs from donors <40 years old and >or=60 years old was 84% and 73%, p = 0.003, respectively. These rates in recipients with cholestatic liver disease and alcoholic liver disease were 85% and 82%, respectively, p = 0.11 and 82% and 78%, respectively, p = 0.14. Three-year graft survival in hepatitis C recipients transplanted from 1994 to 1995 and 1996 to 1999 was 67% and 69%, respectively, p = 0.10. Graft survival in hepatitis C recipients has not declined in recent years. Older donor age is associated with lower short-term graft survival in recipients with hepatitis C, but not in recipients with cholestatic or alcoholic liver disease.
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