Peter Schumacher's research while affiliated with Montanuniversität Leoben and other places

Publications (178)

Article
Full-text available
Effects of Si and Sr on solidification microstructure and thermal conductivity of Al–Si binary alloys and Al–9Si–Sr ternary were investigated, respectively, with a special focus on the relationship between solidification microstructure and thermal conductivity. It was found that (i) in Al–Si binary alloys, with increasing Si content, α-Al grain siz...
Article
The effects of trace transition elements (Mn, Cr, V) on the solidification microstructure and the thermal conductivity of Al-9Si based alloys have been investigated. It was found that the effect of Mn, Cr, V on the solidification behavior and solidification microstructure is mainly related to α-Al grains via affecting heterogeneous nucleation and g...
Article
In order to reduce CO 2 emission and energy consumption, more recycled secondary materials have to be used in foundry industry, especially for Al-Si-Mg based alloys for semi-solid processing. In this paper, Al-Si-Mg based alloys with the addition of recycled secondary materials up to 30 % (10, 20, 30 %, respectively) have been produced by semi-soli...
Article
Different Ta concentrations together with stochiometric grain refiner (Al-2.2Ti-1B) in Al-Si-Mg based alloys were investigated with the aim to elucidate grain refinement mechanisms. Post-solidification microstructure was characterised using optical microscopy and scanning electron microscopy (SEM), with a special focus on the Ta-rich layer (more li...
Article
AZ80 alloy has been widely used to produce high performance Mg casting and wrought parts for high-end applications due to its high mechanical properties and deformation ability. However, at least two important issues still need to be solved in order to further improve its mechanical properties and deformation ability. Firstly, the grain size of α-M...
Article
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The complex metallurgical interrelationships in the production of ductile cast iron can lead to enormous differences in graphite formation and local microstructure by small variations during production. Artificial intelligence algorithms were used to describe graphite formation, which is influenced by a variety of metallurgical parameters. Moreover, c...
Article
Melting or re-melting accompanies solidification in many technical castings. For example, during ingot casting, some crystal fragments or equiaxed grains can enter the superheated region and re-melt, while solidification continues in other regions. Solidification and remelting occurring simultaneously at different locations present an important spe...
Article
The refinement of Al alloys by TiB2 has been extensively investigated for decades, both in industry and academia. In order to achieve higher grain refinement potency, it is known that other solutes must be added alongside TiB2, thus tailoring the heterogeneous nucleation at the interface between the TiB2 particles and the Al matrix. Here, we report...
Article
The casting of liquid melt on a preheated substrate layer to produce a metallurgical compound represents a direct approach towards clad aluminum strips. To investigate this direct process route and the formation of a metallurgical bond at the interface, a small-scale pilot plant to cast pure aluminum on strips of aluminum alloy 7075 under controlle...
Article
The precipitation microstructure of Al-10Si-0.5 Mg-0.5Mn (wt%) alloys with different Zr additions was investigated. The β-type (i.e. Mg2Si) phase was observed to be dominant in the precipitation microstructure. Furthermore, the Q-Al5Cu2Mg8Si6 phase and the π-Al8Mg3FeSi6 phase were also observed to be the dominant thermodynamically stable precipitat...
Article
Sand core samples were subjected to thermal pre-conditioning profiles between 200 and 500 °C both in ambient air and under sealed conditions. These were customised similar to an industrial cast aluminium cylinder head. The samples were investigated via unconfined compression, splitting tensile, shear, and bending tests. The suitability of the data...
Article
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Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are s...
Chapter
A quantitative analysis on the casting defects is of great necessity to further improve the mechanical properties of high-performance alloys, in particular dynamic fatigue properties. Computed tomography (CT) is frequently utilized to determine the casting defects of casting parts and thereby evaluate their casting qualities. In this contribution,...
Article
Inorganic binder systems have found increasing applications, driven by environmental and legal regulatory requirements. As a consequence of their thermal stability, the mechanical core removal process is challenging and not fully predictable, owing to a lack of mechanical fracture energy data. In the present work, the wedge splitting test method wa...
Article
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The solidification behaviour of Al–Si based alloys with controlled additions of Eu (up to 200 ppm) and P (up to 10 ppm) was investigated using thermal analysis in a conventional die casting condition. The results indicate that P may be removed or involved into the formation of EuP phase. Furthermore, the formation of EuP phase appears to have a ben...
Article
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The quality of green sand moulds is paramount for the casting quality and reduction of surface defects. The general knowledge within foundries on green sand properties and its influence on casting defect behaviour has significantly decreased as a result of outsourced external sand testing and dependence on external consultants. Moreover, academic R...
Article
Modelling of the evolution of microstructure during processing enables the deeper understanding of synergetic influence of various processing parameters that influences on the evolution of microstructure. The aim was to develop aluminium casting alloy, which have improved mechanical properties, while reducing the weight of the finished product used...
Conference Paper
Precipitation hardening is one of the dominant strengthening mechanisms for Mg alloys, especially for Mg alloys containing rare earth elements. However, precipitation hardening of conventional Mg alloys (such as AZ91D, ZK60 or even WE54/43) is relatively weaker than in high performance Al alloys [such as Al–Cu–Mg based alloys (2024) and Al–Zn–Mg–Cu...
Article
Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), re...
Article
The here presented criterion describes the disintegration kinetics of cast in sand cores, which is influenced by transient thermal and mechanical casting process loads. A semi-permanent mould setup allowing for various thermal exposure intensities was developed and used with wedge shaped, hot hardened silicate bonded sand cores. During defined mech...
Article
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Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the grow...
Article
Eine Ultraschallbehandlung stellt eine effiziente Möglichkeit zur Entgasung von Aluminiumschmelzen dar. Während die Entgasungswirkung allgemein anerkannt ist, ist der Effekt einer Aufgasung nach einer Ultraschallbehandlung kaum untersucht. Diese Arbeit verfolgt das Ziel, den Effekt einer künstlichen Aufgasung nach einer Ultraschallbehandlung zu unt...
Article
Im Gegensatz zum System der Aluminiumlegierungen, in dem das Gebiet der Kornfeinung umfassend untersucht und deren Wirkung allgemein bekannt ist, ist das System der Kupferlegierungen nur zu einem geringen Maße untersucht, vor allem in Bezug auf deren grundlegenden Mechanismus zur Kornfeinung. Es wird angenommen, dass die Kornfeinungswirkung möglich...
Article
The Heterogeneous Nucleation Sequence at the Interface of TiB2 in Al Alloys - Volume 23 Issue S1 - Jiehua Li, Fredrik S. Hage, Quentin M. Ramasse, Peter Schumacher
Article
The microstructure evolution of the K403 Ni-based superalloy as a function of thermal exposure temperature and time was investigated using correlative characterization, including a combination of scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, high-angle angular dark-field scanning transmission elec...
Article
High angle annular dark field scanning transmission electron microscope imaging and electron energy loss spectroscopy were used to elucidate the heterogeneous nucleation interface of AlB2 in an Al-7Si alloy. Si particles were observed in the vicinity of a AlB2 particle, but no significant Si-B-rich layer (such as SiB6) was observed at the interface...
Article
High angle annular dark field scanning transmission electron microscope (HAADF-STEM) imaging and quantitative energy-dispersive X-ray spectroscopy (EDX) analysis was used to elucidate the Cu segregation on the interface between Al2O3 substrate and Al-1.4Cu alloy. A significant Cu segregation (about 2 at%) was observed, which can be mainly attribute...
Article
High angle annular dark field scanning transmission electron microscope imaging and electron energy loss spectroscopy was used to elucidate the elemental distribution (Gd, Zn, Mn) within the long-period stacking ordered (LPSO) structure in a Mg-15Gd-0.8Zn-0.8Mn (wt%) alloy. While Gd and Zn enrichment was observed within the LPSO structure, no signi...
Article
This review features the potential of modern high spatial resolution methods in materials science and engineering by presenting a selection of scientific examples covering bulk materials, as well as hard coatings, semiconductors, and mesoporous thin films. Complementary techniques are employed to study microstructure and/or texture and stresses in...
Article
The growth restriction factor Q of the alloying elements of the Cu-system was determined using thermodynamic software tools to obtain accurate Q-values. A comprehensive list was given for a nominal solute content of 1 wt-%. Based on the calculations, melting experiments were carried out under defined casting conditions given by the TP-1 test to eva...
Chapter
The grain refinement of Al alloys has been extensively investigated for several decades both in industry and academia, not only through attempts at developing efficient grain refiners, but also with a view to achieve a better understanding of the grain refinement mechanism [1-7]. The addition of Al-Ti-B grain refiners (e.g. Al-5Ti-1B, wt. %) during...
Article
Precipitation of long-period stacking ordered (LPSO) structure in Mg-15Gd-0.8Zn-0.8Mn (wt%) alloy after solution treatment at 520°C for 1000h has been investigated using high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The stacking periodicity of the LPSO phase is lengthened 14-fold along the c-axis and the LPSO...
Article
Improved understanding of foundry sand core properties is a key requirement for high precision casting process development. The present work demonstrates the potential to evaluate mechanical and functional sand core properties using precisely acquired 3-point bending test load curve data applying standard bending test geometries. Four organic binde...
Article
Full-text available
Foundry alloys with Al-based matrices have a wide range of uses in today's global economy and there is a high demand for castings of Al alloys, including Al-Zn alloys. In this paper, investigations on the grain refinement of high-Zn aluminium cast alloys are presented. Aluminium alloys with relatively high zinc content have a tendency to be coarse-...
Article
Ultrasonic treatment of aluminium melts is known as an efficient process to remove dissolved hydrogen. Whereas the degassing efficiency of ultrasonic treatment has been extensively reported, the effect of re-gassing after the ultrasonic treatment is much less studied. The present investigation attempts to evaluate the effect of artificial re-gassin...
Article
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Effects of trace elements (0.2Y and 0.2Ca (wt%) on the eutectic Ge in high purity Al–20Ge (wt%) alloys were investigated by multi-scale microstructure characterization techniques. Particularly, the distribution of trace elements (Y and Ca) within the eutectic Ge and/or at the interface between eutectic Ge and eutectic Al was investigated by atomic...
Article
Full-text available
Improved understanding of foundry sand core properties is a key requirement for high precision casting process development. The present work demonstrates the potential to evaluate mechanical and functional sand core properties using precisely acquired 3-point bending test load curve data applying standard bending test geometries.
Article
Atom probe tomography was used to compare Na and Sr modified Al–Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 ± 0.46 and an Al:Na ratio of 1.07 ± 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at...
Article
Full-text available
The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale....
Article
Mg–5Zn–2Gd–0.4Zr alloy (wt. %) shows a significant age hardening response with a hardness increment from 62 HV to 72 HV by ageing at 200 °C for up to 80 h. Transmission electron microscopy and atom probe tomography characterizations reveal that precipitates with different morphologies and habit planes form in the alloy, including triangular-shaped...
Article
Full-text available
The nucleation and growth of primary Al3Sc phase has been investigated in high purity Al alloys and commercial purity Al alloys, with a special focus on the impurity effects. In the case of high purity Al alloys, most primary Al3Sc phases were pushed to grain boundaries during moving solidification front. Such type of primary Al3Sc phase does not c...
Article
Full-text available
Entrained droplet technique and DSC analyses were employed to investigate the influence of trace elements of Sr, Eu and P on the heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-5wt.% Si alloys. Sr and Eu addition was found to exert negative effects on the nucleation process, while an increased undercooling was observed...
Article
Full-text available
In this research work, a modified energy efficient T6 heat treatment was performed on AlSi7Mg0.3 and AlSi9Cu3(Fe) castings produced on pilot scale, where a part of the heat from the casting process was used during solution annealing. Calculations of the possible energy savings showed that the novel energy saving heat treatment can gain up to 260 kJ...
Chapter
The addition of CrB2 and Sr into Al-10Si-0.3Mg (wt.%) based alloys not only modify the eutectic Si, but also refine the eutectic grains. CrB 2 particles were found to nucleate the eutectic grains, despite the AlP particles being partly removed or depleted by the interaction between Sr and AlP. Furthermore, P level was found to be one of the dominan...
Chapter
A new belt casting process has been developed to cast aluminum-al uminum alloy compound strips. The first strip is cast by a conventional glass fiber belt caster. At a defined distance from the location of the primary solidification, a second casting unit is placed. The local upper surface temperature of the s ubstrate is essential for the forming...
Chapter
Grain refinement by inoculation is well established in Al alloys and the benefits of grain refinement are widely acknowledged. In contrast in the Cu-system, there has been little practical work performed on the grain refinement of Cu-based alloys. Moreover, there is a lack of detailed investigati on to understand the grain refinement mechanism in C...
Article
The addition of CrB2 and Sr into Al-10Si-0.3 Mg (wt.%)-based alloys not only modify the eutectic Si, but also refine the eutectic grains. CrB2 particles were found to nucleate the eutectic grains, despite the AlP particles being partly removed or depleted by the interaction between Sr and AlP. Furthermore, P level was found to be one of the dominan...
Chapter
This paper investigates the effect of ZrB2 particles on the grain refinement of an Mg-Al alloy. A comparison, with respect to grain size, of the effect of ZrB2 particles formed in situ and commercially obtained synthetic ZrB2 particles, which are subsequently added to the melt, was made. In situ ZrB2 particles were formed by reacting conventional A...
Chapter
Crystallization from a melt and from a metallic glass both occur in an undercooled liquid. In this way identical nucleation mechanisms can operate in the two cases. However, in metallic glasses, unlike conventional solidification at low undercooling, the low atomic mobility permits the resolution and microscopical study of nucleation processes on a...
Chapter
A new belt casting process has been developed to cast aluminum-aluminum alloy compound strips. The first strip is cast by a conventional glass fiber belt caster. At a defined distance from the location of the primary solidification, a second casting unit is placed. The local upper surface temperature of the substrate is essential for the forming of...
Chapter
Grain refinement by inoculation is well established in Al alloys and the benefits of grain refinement are widely acknowledged. In contrast in the Cu-system, there has been little practical work performed on the grain refinement of Cu-based alloys. Moreover, there is a lack of detailed investigation to understand the grain refinement mechanism in Cu...
Chapter
In order to elucidate the detrimental effect of high Si contents on the grain refinement of Al alloys, the heterogeneous nucleation of α-Al in an Al70Ni13Si17(at.%) alloy was studied using a novel metallic glass technique. A Ti-B-Al 5:1 grain refiner rod containing TiB2particles, on which Al3Ti layers were detected, was added to an Al70Ni13Si17melt...
Chapter
Modification of eutectic Si from platelet to fibrous morphology can be interpreted using impurity-induced twinning (IIT) growth mechanism and twin plane re-entrant edge (TPRE) growth mechanism. According to IIT mechanism, Yb has an exactly fitting radius ratio (1.646). However, to date, the effects of Yb additions on eutectic Si is still very limit...
Chapter
The present work shows a possible method for refining the micro structure of AlMgSi cast alloys in a similar fashion to the method which has been state of the art for many years in the case of hypoeutectic AlSi alloys.
Chapter
The addition of CrB2 and Sr into Al-10Si-0.3Mg (wt.%) based alloys not only modify the eutectic Si, but also refine the eutectic grains. CrB2 particles were found to nucleate the eutectic grains, despite the AlP particles being partly removed or depleted by the interaction between Sr and AlP. Furthermore, P level was found to be one of the dominant...
Chapter
The poisoning mechanism of Zr was investigated using a metallic glass technique. Grain refining particles from a 5:1 TIBAL rod were embedded into a metallic glass produced by melt-spinning an Al87Ni10Zr3 (at.%) alloy. Within the as-quenched samples, dendrites of a-Al were found on TiB2 particles and on primary dendrites of Al3Zr competing to nuclea...
Article
Structural modification of high-zinc aluminium alloys influences their strength and damping properties. In a series of studies, Al – 20 wt. % Zn alloy (Al-20Zn) has been doped with Ti introduced with ZnTi-based master alloy. The alloy structure and mechanical properties have been studied using: SEM (scanning electron microscopy), LM (light microsco...
Article
Full-text available
Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are va...
Article
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This work presents two three-dimensional solidification models, which were solved by several commercial solvers (MAGMASOFT, FLOW-3D, ProCAST, WinCast, ANSYS, and OpenFOAM). Surprisingly, the results show noticeable differences. The results are analyzed similar to a round-robin test procedure to obtain reference values for temperatures and their unc...
Article
Full-text available
Three dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al3(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (...
Article
The solute adsorption and/or segregation as well as the solute entrapment of Sr, Na and Yb atoms during eutectic Si growth in a series of high-purity Al–5 wt.% Si alloys was investigated by multi-scale microstructure characterization techniques, including high-resolution transmission electron microscopy and atomic-resolution scanning transmission e...
Article
Three hypoeutectic Fe containing Al-Si-Mg alloys for casting crash relevant automotive components are experimentally investigated. The comparatively short heat treatments include solutionising at 540 degrees C for 5 min or at 465 degrees C for 60 min respectively, compressed air quenching and artificial aging at 223 degrees C for 120 min. Character...
Article
Al-5 wt pct Si-based alloys with Na additions (19 and 160 ppm) have been produced by controlled sand casting and melt spinning. Entrained droplet technique and differential scanning calorimetry were employed to investigate the nucleation behavior of eutectic Si. High-resolution transmission electron microscopy and atom probe tomography were used to...
Article
Full-text available
Al–5 wt.% Si-based alloys with 0.05 wt.% Eu addition were produced by controlled sand-casting and melt-spinning, respectively. The modification of eutectic Si caused by 0.05 wt.% Eu addition was investigated by thermal analysis, differential scanning calorimetry and multi-scale microstructure characterization techniques. In the case of controlled s...
Article
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The effects of combined additions of Ca and P on the eutectic Si in a series of high purity Al-5 wt pct Si alloys have been investigated with the entrained droplet technique and complementary sets of conventional castings. Differential scanning calorimetry (DSC) and thermal analysis were used to investigate the eutectic droplet undercooling and the...
Article
Impurity effects on the nucleation and growth of primary Al3(Sc,Zr) phase have been investigated in high purity Al alloys and commercial purity Al alloys, respectively. In the case of high purity Al alloys, primary Al3(Sc,Zr) phases were found to be pushed to grain boundaries ahead of the solidification front. Such type of primary Al3(Sc,Zr) phase...
Article
Full-text available
Two individual high-pressure die casting geometries were developed to study the influence of process parameters and alloy composition on the distortion behavior of aluminum alloy castings. These geometries, a stress lattice and a V-shaped lid, tend to form residual stress due to a difference in wall thickness and a deliberate massive gating system....
Article
A series of high-purity Al–5 wt.% Si alloys with trace additions of Sr, Fe and P were prepared by using arc-melting and subsequent melt-spinning. The nucleation phenomenon incorporating the free growth criterion of eutectic Si was investigated by using the entrained droplet technique, atomic resolution scanning transmission electron microscopy and...
Article
Full-text available
The paper provides a new insight into the modification of eutectic Si in Al-Si based alloys. To date, impurity-induced twinning mechanism and twin plane re-entrant edge mechanism are the well-accepted theories. However, neither IIT nor TPRE can be used to interpret all modification observations. Therefore, a re-consideration of modification mechani...
Article
Full-text available
The simulation of macrosegregation in a 2.45-ton steel ingot with the three-phase mixed columnar-equiaxed model was presented previously. The results showed an overestimation of the intensity of bottom negative segregation. The reason is due to the assumed globular morphology for the equiaxed crystal. Therefore, in this paper a simple approach is s...
Article
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Experimental evidence [Ohno 1987] revealed the influence of some pouring techniques on the as-cast structure. In the current work the process of pouring of the molten Al-4.0 wt.%Cu via one or multiple streams into a graphite mold is studied using a 3-phase model by considering the nucleation, the initial growth and transport of globular equiaxed cr...
Article
This paper investigates the effect of ZrB2 particles on the grain refinement of an Mg-Al alloy. A comparison, with respect to grain size, of the effect of ZrB2 particles formed in situ and commercially obtained synthetic ZrB2 particles, which are subsequently added to the melt, was made. In situ ZrB2 particles were formed by reacting conventional A...
Article
The intermetallic phase selection during homogenization in a AA6082 alloy has been investigated. A short homogenization treatment at 580 {\degr}C for 4 h and a subsequent slow cooling with a rate of about 8 {\degr}C/min, rather than a conventional quick quenching into water, results in the formation of the rounded discrete Al15(FeMnCr)3Si2 phase, w...
Article
To describe the solute effect on grain refinement, the growth restriction factor (Q) in multicomponent multiphase Al alloys has been often evaluated using a simple summation of the Q values of the individual constituents taken from the binary alloy diagram. Such kind of evaluation can lead to mistakes, or completely fail when an intermetallic phase...
Article
Full-text available
In this thesis the artificial ageing of the heat treatment process and the effects of the heat treatment on microstructure and material properties at different temperatures and times were investigated for the aluminium casting alloy AlMg5Si2Mn. An optimal choice of the temperature and time parameters for the heat treatment can activate certain meta...
Chapter
To describe the solute effect on grain refinement, the growth restriction factor (Q) in multicomponent multiphase Al alloys has been often evaluated using a simple summation of the Q values of the individual constituents taken from the binary alloy diagram. Such kind of evaluation can lead to mistakes, or completely fail when an intermetallic phase...