Search Results (155)

The liquidus and solidus temperatures, the initial temperature of the solidification of binary eutectics, and the partition ratios of the solid solution at the Al corner of the ternary eutectic-type Al-Si-Cu alloy system were calculated using the thermodynamically based ESTPHAD method. It is shown that these data can be calculated from the liquidus and solidus data of the two binary equilibrium phase diagrams (first estimation), the binary phase diagram and the eutectic valleys in the ternary system (second estimation), as well as the binary phase diagram, the eutectic valleys, and one (third estimation) and more (fourth estimation) liquidus and solidus temperatures of the ternary equilibrium phase diagram with varying precisions. A database calculated with Thermo-Calc software (version 4.1.0.4995), was used for the calculations. Full article

This study systematically investigates the effects of Fe and Si impurities on the microstructure and mechanical properties of Al-Cu-Li alloys. Five alloy compositions with controlled Fe (0.03–0.12 wt.%) and Si (0.03–0.12 wt.%) contents were fabricated and processed through homogenization, hot extrusion, solution treatment, and aging. Microstructural characterization demonstrates that Fe promotes the formation of coarse skeletal Al₇Cu₂Fe intermetallics, while Si facilitates the precipitation of blocky α-AlFeSi phases and eutectic Si particles. An elevated Fe content substantially deteriorates strength, ductility, and fracture toughness, primarily due to two mechanisms: the persistence of thermally stable impurity phases that serve as stress concentrators and preferential crack initiation sites throughout thermomechanical processing, and the consumption of Cu that reduces the volume fraction of primary T₁ (Al₂CuLi) strengthening precipitates. In contrast, Si exhibits comparatively moderate detrimental effects. The findings establish that stringent Fe control is essential for maintaining mechanical performance, whereas strategic Si adjustment offers a viable approach for cost management in recycled alloy production. Full article

Al-Ni alloys have a unique set of properties including high conductivity, high fluidity, good thermal stability, and reasonable strength. These properties are also needed for effective braze fillers, a novel application for Al-Ni alloys. A Cu substrate was reacted with pure liquid Al, and the resulting microstructure upon solidification was observed and analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). This diffusion couple was compared with the diffusion couple between liquid eutectic Al-3at.%Ni and a Cu substrate. Several phases unique to the solidified liquid in the Al-Ni/Cu diffusion couple were observed, such as Al₇Cu₄Ni (τ), Al₃(Cu, Ni)₂, and Al₃Ni. These microstructures were compared with a mathematical model based on Fick’s second law, as well as calculation of phase diagram (CALPHAD) modelling. The approximate calculated concentration profile of Cu in the liquid phase was validated against the microstructural observations and proved effective to explain the observed microstructural features. Liquid Al-3at.%Ni was found to limit the growth of the brittle Al₂Cu (θ) phase during solidification by limiting Cu solubility in the liquid phase, which would be beneficial for use in dissimilar joints between Al and Cu. Full article

Aluminum (Al) powder with low sinterability is difficult to use in binder jetting (BJT) additive manufacturing, which involves sintering a metal powder after forming a green body. A liquid-phase sintering process for Al powder using Al–Cu eutectic alloy powder as a sintering aid has recently been developed. In this study, to clarify the applicability of liquid-phase sintering to BJT additive manufacturing, the effect of the initial relative density of green bodies (ρ_rel,0 = 50–90%) on the final relative density was investigated. The final relative density was not significantly affected by ρ_rel,0 and achieved 96–97% after sintering at 630 °C for 1800 s. However, pores are likely to remain in the sintered body with a high ρ_rel,0 of 90%. In situ observations using synchrotron radiation X-ray computed tomography revealed that large pores were formed at the early sintering stage of the green body with ρ_rel,0 of 90% and partially retained after sintering. By contrast, the green body with ρ_rel,0 of 50% exhibited a significant rearrangement at the early sintering stage, promoting the densification. This study provides a deep understanding of liquid-phase sintering of Al powder, which is considered a suitable post-processing method for BJT additive manufacturing. Full article

A non-standardized hypereutectic aluminum–silicon alloy, AlSi18Cu3CrMn, was developed. To refine the structure of the studied composition, a phosphorus modifier was used in an amount of 0.04 wt %, and a complex modifying treatment was applied by combining the chemical elements of phosphorus, titanium, boron and beryllium (P, 0.04 wt %; Ti, 0.2 wt %; B, 0.04 wt %; Be, 0.007 wt %). To improve the mechanical and operational properties of the alloy, it was heat-treated (T6) at a temperature of 510–515 °C before quenching, with artificial aging applied at a temperature of 210 °C for 16 h. Phosphorus-modified alloy AlSi18Cu3CrMn was quenched in water at 20 °C, and the combined modified alloy was quenched in water at temperatures of 20 °C and 50 °C. By conducting a microstructural analysis, the free Si crystals and silicon crystals in the composition of the eutectic in the alloy structure were characterized, and by conducting XRD, the presence and type of secondary phases were established. The hardness of the alloy was measured, as well as the microhardness of the α-solid solution. Static uniaxial tensile testing was carried out at normal and elevated temperatures (working temperatures of 200 °C, 250 °C and 300 °C). By using a gravimetric method, the corrosion rate of the alloy in 1 M NaCl and 1 M H₂SO₄ was calculated. The mass wear, wear intensity and wear resistance of the studied AlSi18Cu3CrMn alloy were determined during reversible reciprocating motion in the boundary-layer lubrication regime. Full article

The room-temperature and high-temperature microstructural characteristics and tensile properties of an Al-12Si-4Cu-2Ni-0.5Mg piston alloy modified with calcium (Ca; denoted as AC sample) or phosphorus (P; denoted as AP sample) under different heat treatment conditions were systematically analyzed. Under Ca modification, the second-phase network structure of the alloy was adjusted and strengthened by an Al-TCB master alloy. Eutectic silicon (Si) particles in the AC sample possessed a fibrous structure, whereas the AP sample contained elongated eutectic Si particles, and Ca modification was found to be a potential method for simultaneously enhancing the strength and plasticity of the alloy to a matching degree at high temperatures. The T6 treatment noticeably increased the density of nanoscale precipitates; however, it also disrupted the growth of the second-phase network structure. Micron and submicron C-TiB₂ and Al₄C₃ particles formed by the in-situ reaction of TCB particles acted as bridging phases within the second-phase network structure and enhanced the strength of the piston alloy. The ultimate tensile strength of the alloy at 350 °C increased from 74 to 101 MPa, representing a 36.5% enhancement. A comprehensive analysis revealed that Orowan strengthening was the main strengthening mechanism of the alloy at room temperature, whereas load transfer and network structure strengthening were the dominant strengthening mechanisms at high temperatures. Full article

Although low-silicon Al-Si alloys have been extensively studied, further improvement in their mechanical performance remains a critical challenge. This study examines the synergistic effects of scandium (Sc) and zirconium (Zr) additions on the solidification behavior, microstructural evolution, and mechanical properties of Al-5Si-Cu-Mg alloys. The Sc/Zr additions refine the α-Al grains and modify the eutectic Si morphology, with the most uniform microstructure obtained at 0.5 wt.% due to the formation of coherent Al₃(Sc,Zr) dispersoids. These additions also suppress the formation of needle-like β-Al₅FeSi phases and promote the transformation to compact α-Al₁₅(Fe,Mn)₃(Si,Zr,Sc)₂ intermetallics, optimizing the solidification process. The yield strength increases with Sc/Zr content owing to grain-boundary and precipitation strengthening. However, the alloy without Sc/Zr exhibits the highest ultimate tensile strength and elongation, likely due to its finer secondary dendrite arm spacing and the absence of casting-induced cracks in this investigation. Although Sc/Zr additions of 0.25–0.5 wt.% contribute to microstructural refinement, the concurrent formation of porosity and coarse intermetallic compounds leads to a deterioration in ductility. Excessive Sc/Zr additions further coarsen grains and degrade the overall mechanical integrity. Full article

Discarded NdFeB permanent magnets will become a significant source of rare earth elements (REEs) in the future. Electric vehicle (EV) motors utilize 2–5 kg of NdFeB magnets, and researchers are prioritizing the development of suitable extraction technologies. The objective of our research is to separate metal materials (Al, Cu, Fe and FEEs) from EV motors, based on their melting temperatures. REE magnets that pose the greatest challenge are melted together with the electrical steel of the motor, and the potential for extracting REEs in a selective manner from the molten steel was examined based on their significant oxidation potential using FeO–SiO₂ compounds, which act as an oxidizing slag-forming agent, to test the extraction method. Fayalite (2FeO·SiO₂) is the most easily created and ideal eutectic compound for carrying oxygen (FeO) and forming slag (${\mathrm{S}\mathrm{i}\mathrm{O}}_4^{4^{-}}$), typically generated during copper smelting. In this experiment, copper slag was used and the results were compared to a smelting test, which had previously used a synthesized fayalite flux as a model. The smelting test, utilizing synthesized fayalite flux, yielded a 91% Nd recovery rate. The Nd recovery rate in the smelting test with copper slag hit a high of 64.81%, influenced by the smelting’s holding time. The steel contained 0.08% Nd. Iron was recovered from the copper slag at a rate of 73%. During the smelting test, it was observed that the reaction between Nd₂O₃ and the Al₂O₃ crucible resulted in the formation of a layer on the surface of the crucible, diffusion into the crucible itself, and a subsequent reduction in the efficiency of Nd recovery. Full article

During active brazing of alumina ceramics, active elements react with the ceramic to form a reaction layer, which has significant influence on the mechanical property of the brazed joint. However, the composition and formation mechanism of this layer remain unclear among researchers. To fill this gap, different brazing temperatures (900–1100 °C) and heating rates (2.5 °C/min and 10 °C/min) were used to braze 95% Al₂O₃ ceramics and a Kovar 4J34 alloy using a Ag-Cu-2Ti active brazing filler, and the microstructure and mechanical properties of the joints were investigated. The results show that the joint could be divided into five layers: Al₂O₃, ceramic-side reaction layer, filler layer, Kovar-side reaction layer, and Kovar. The ceramic-side reaction layer could be further divided into a Ti-O-rich layer and an intermetallics (IMC)-rich layer, and the Kovar-side reaction layer consists of TiFe₂ particles, Ag-Cu eutectic, and the remaining Kovar. A belt-like TiFe₂+TiNi₃ IMC could be found in the filler layer. Increasing the brazing temperature enlarged the belt-like TiFe₂+TiNi₃ IMC in the filler layer and increased the thickness of the IMC-rich layer in the ceramic-side reaction layer, but had no significant effect on the thickness of the Ti-O-rich layer in the ceramic-side reaction layer. A lower heating rate (2.5 °C/min) was found to suppress the formation of the IMC-rich layer and shift the fracture location in shear tests from the ceramic-side reaction layer to the filler layer, indicating that the strength of the ceramic-side reaction layer was enhanced by controlling the formation of the IMC-rich layer. A maximum shear strength of 170 ± 61 MPa was obtained at a heating rate of 2.5 °C/min and a brazing temperature of 940 °C. Full article

Tribological tests were conducted on eutectic white cast iron subjected to directional solidification (resulting in a directionally oriented microstructure) and, for comparison, on white cast iron with an equiaxed (non-directional) structure. The tests were performed under dry sliding conditions on a pin-on-block rig using Cu, AlSi12CuNiMg alloy, AlSi12CuNiMg + SiC composite, and steel grade 1.3505. The friction coefficient and wear rates of these materials were systematically compared. Quantitative and qualitative evaluations of the wear tracks formed on the test specimens were carried out using profilometry. The results demonstrate that the directionally solidified white cast iron exhibits improved friction coefficient stability and reduced wear in the specific tribological pairs. The oriented directional structure demonstrated more favourable interactions when paired with AlSi12CuNiMg + SiC composite and 1.3505 steel. These tribological combinations exhibited reduced roughness values across selected cross-sectional analyses, resulting in correspondingly lower Sa parameter measurements. This finding suggests a promising new application for inserts made of directionally structured white cast iron in structural components requiring enhanced wear resistance at elevated temperatures. Full article

Al-Cu3-Si-Mg alloy prepared by molten metal die forging (MMDF) under a pressure of 118 MPa was solution-treated at different temperatures and times, and the evolution behavior of the non-equilibrium eutectic in the microstructure was observed using an optical microscope and scanning electron microscope. The results show that the initial solidification structure of Al-Cu3-Si-Mg before solution treatment consists of irregular eutectic (α+Al₂Cu), strip compound Q (Al₅Cu₂Mg₈Si₆), polygonal phase φ(Al_xTi₉La₂Ce₆Cu), spherical particle θ(Al₂Cu) and cross-shaped β(Mg₂Si) near the grain boundary. After solution treatments, the irregular eutectic at grain boundaries is dissolved. In the solution temperature range of 480 °C~510 °C, the irregular eutectic fraction decreased with the increase in solution temperature, and the grain size of other compounds such as Q (Al₅Cu₂Mg₈Si₆) and the spherical particle phase θ(Al₂Cu) also showed a decreasing trend. However, all phases do not change significantly with the increase in solution temperature when the solution temperature is between 510 °C and 540 °C. It was determined experimentally that the holding time of 30 min at each temperature is the solution limit. Based on the experimental results, a dissolution model of intergranular irregular eutectic was established as ${\displaystyle \frac{dE}{dt}}=-{\displaystyle \frac{4P\sqrt{\pi tD}+2rk}{kPD}}$. Full article

This study reported the development of a novel Al-Si-Mg-based composite reinforced by micron-sized Cu-Mn binary solid solution phases and submicron-sized α-Al(Mn,Fe)Si dispersoids. The Cu-Mn binary solid solution phases were added to the melt in the form of an Al-3%CuMn master alloy, whereas α-Al(Mn,Fe)Si dispersoids were obtained via heat treatment. The microstructure analysis confirmed the presence of micron-sized Cu-Mn binary, eutectic Mg₂Si, and Al₁₅(FeMn)₃Si₂ intermetallic phases, submicron-sized α-Al(Mn,Fe)Si dispersoids, and nano-sized precipitates in the Al-based composite. At room temperature, tensile results represented a yield strength of 287 MPa and a tensile strength of 306 MPa, with an elongation of 17%. Moreover, the Al-based composite maintained a yield strength of 277 MPa up to 250 °C, with a slight increase in elongation. The composite also exhibited excellent high-temperature high-cycle fatigue properties and showed a high-cycle fatigue limit of 140 MPa at 130 °C, which is ~2.3 times higher than that of the commercial A319 alloy. A fractography study revealed that the secondary particles hindered the movement of dislocations, thus delaying crack initiation under cyclic loading at high temperatures. Additionally, Cu-Mn binary solid solutions and Al₁₅(FeMn)₃Si₂ phases were found to be effective in reducing the crack propagation rate by hindering the movement of the propagated crack. Full article

Understanding the limitations of cold-formed aluminum alloys in practice applications is essential, particularly due to the risk of substructural changes and a reduction in strength when exposed to elevated temperatures. In this study, the thermal stability of the ultra-fine-grained (UFG) structure formed by equal channel angular pressing (ECAP) at room temperature and the mechanical properties of the AlSi7MgCu0.5 alloy were investigated. Prior to ECAP, the plasticity of the as-cast alloy was enhanced by a heat treatment consisting of solution annealing, quenching, and artificial aging to achieve an overaged state. Four repetitive passes via ECAP route A resulted in the homogenization of eutectic Si particles within the α-solid solution, the formation of ultra-fine grains and/or subgrains with high dislocation density, and a significant improvement in alloy strength due to strain hardening. The main objective of this work was to assess the microstructural and mechanical stability of the alloy after post-ECAP annealing in the temperature range of 373–573 K. The UFG microstructure was found to be thermally stable up to 523 K, above which notable grain and/or subgrain coarsening occurred as a result of discontinuous recrystallization of the solid solution. Mechanical properties remained stable up to 423 K; above this temperature, a considerable decrease in strength and a simultaneous increase in ductility were observed. Synchrotron radiation X-ray diffraction (XRD) was employed to analyze the phase composition and crystallographic characteristics, while transmission electron microscopy (TEM) was used to investigate substructural evolution. Mechanical properties were evaluated through tensile testing, impact toughness testing, and hardness measurements. Full article

In this study, prospects of designing new Al–Ca–Cu–Mn (Zr) alloys for additive manufacturing (AM) were evaluated for the example of laser remelting of thin-sheet rolled products. The new as-cast alloys have a hypereutectic structure containing Al₂₇Ca₃Cu₇ primary crystals and ultrafine eutectic particles of (Al,Cu)₄Ca and Al₂₇Ca₃Cu₇ phases in equilibrium with the aluminum solid solution. The solid solutions are additionally strengthened by alloying with Mn and micro additions of Zr, which contribute to the formation of coarsening-resistant phases without compromising the manufacturability of the alloys. Laser remelting, which simulates AM-typical solidification conditions, promotes the formation of a pseudoeutectic cellular structure without the occurrence of undesirable primary Al₂₇Ca₃Cu₇. The size of the dendritic cells and eutectic particles is 10 times smaller (for solidification rates of ~200 K/s) than that of the as-cast state. This structure provides for a higher hardness of the laser-remelted alloy (96 HV) as compared to the as-cast alloy (85 HV). Data for the alloy after 350–400 °C long-term annealing for up to 100 h show that the hardness of the Al–Ca–Cu–Mn–Zr alloys declines relatively slowly by ~7.5% as compared to the Zr-free alloy, whose hardness decreases by ~22%. Thus, one can consider these alloys as a promising candidate for AM processes that require high thermal stability. Full article

The present study examines the structure, properties and use of complex-alloyed hypereutectic aluminium-silicon alloys, emphasising the control of the morphology of primary silicon via treatment with various modifiers as well as their effects on its shape and distribution. Furthermore, this study reviews the experimental work related to the simultaneous modification of primary and eutectic silicon, which leads to the conclusion that favourable results can be obtained by complex modification treatment involving first- and second-type modifiers. After being cast, the AlSi18Cu3CrMn and AlSi18Cu5Mg non-standardised piston alloys are subjected to T6 heat treatment intended to enhance their mechanical performance, harnessing the full potential of the alloying elements. A microstructural analysis of the shape and distribution of both primary and eutectic silicon crystals following heat treatment was employed to determine their microhardness. Full article