Constitutive behavior of an AA4032 piston alloy with Cu and Er additions upon high temperature compressive deformation

The Research and Researchers for Industry (RRi); King Mongkut’s University of Technology Thonbur

Microstructure evolution of an Al–Fe–Ni alloy with Zr and Sc additions upon different cooling rates during solidification for improving the mechanical and electrical conductivity properties

Al–Fe–Ni eutectic alloys have high potential for being alternative aluminum alloys for various electronic and electrical applications instead of conventional low-conductivity Al casting alloys. Furthermore, the addition of Zr and Sc up to 0.3–0.6 wt% improves the hardness for high temperature applications, which is a result of the finer Al–Fe–Ni eutectic structure, and precipitation hardening of Al3Zr and/or Al3Sc nanoprecipitates. Thus, the aim of the present contribution is to analyze the microstructure features changes in an Al-1.75Fe–1.25Ni eutectic alloy upon different cooling rates during solidification. The features of Al–Fe–Ni eutectics and intermetallics were studied quantitatively, and the mechanical properties and electrical conductivity were measured

Constitutive behavior of an AA4032 piston alloy with Cu and Er additions upon high-temperature compressive deformation

Aluminum piston alloys of the AA4032 type are produced by direct-chill (DC) casting an

Effects of ultrasonic melt processing on microstructure, mechanical properties, and electrical conductivity of hypereutectic Al–Si, Al–Fe, and Al–Ni alloys with Zr additions

Ultrasonic melt processing (USP) technique was used to study the effect of Zr addition on the structure refinement and mechanical properties of hypereutectic binary alloy in three different alloys (Al–Si, Al–Fe, and Al–Ni) as potential alternatives to the Al–Si eutectic system especially for high-temperature applications. Mechanical properties of these alloys were controlled through both structure refinement by USP and also Al3Zr nano-precipitation hardening. Significant refinement of primary intermetallics was achieved under USP during the Al3Zr formation in solidification process. The residual Zr in the aluminium solid solution enabled precipitation hardening at 450 °C. As a result, the tensile properties, especially ductility, were considerably improved at room and elevated temperatures. The mechanical properties were analyzed with respect to the volume fraction of intermetallic phases. Electrical conductivity was measured to better explore their potential applications. The effects of alloying elements and structural changes on the mechanical behaviour and electrical conductivity were discussed

Structure modification upon ultrasonic processing of an AA4032 piston alloy: comparison of permanent mold and direct-chill casting

Piston Al-Si alloys have very complex compositions and multi-phase heterogeneous structure, so it is necessary to control the formation of primary and eutectic compounds. In this study, the ultrasonic melt processing (USP) of a eutectic Al-Si piston alloy (AA4032-type) was performed in a permanent mold and during direct-chill (DC) casting to study its effects on the structure refinement and modification. The principal difference between these two ways of casting is that in the permanent mold the solidification front progressively moves towards the ultrasound source, while in the DC casting the position of the solidification front is fixed in space. The results showed that the USP can successfully refine primary Si, Fe-containing intermetallics and aluminum grains. Refinement of primary Si was accompanied by the increase in its amount, which was attributed to both enhanced heterogeneous nucleation and fragmentation. The refinement of Fe-containing intermetallics and Al grains resulted from the fragmentation mechanism and were more pronounced when USP was applied below the liquidus temperature in the permanent mold. However, the eutectic phases coarsened upon USP, and this effect was most pronounced when USP was applied to the semi-solid material. This was related to the strong attenuation of acoustic waves, which effectively heats the semi-solid material and induces corresponding coarsening of the phases. Acoustic streaming induced by an oscillating sonotrode affected the depth of the sump while simultaneously decreasing the macrosegregation, which reflects the dominant role of the melt flow directed against natural convection. The results demonstrated the importance of the solidification stage at which the USP was applied and the specifics of the USP mechanisms acting at the different stages of solidification

Microstructure and elevated temperature mechanical properties of a direct-chill cast AA4032 alloy with copper and erbium additions

Billets from an AA4032 alloy are usually produced by direct-chill (DC) casting to subsequently manufacture piston components by hot forging process. This work presents the effect of combined copper (Cu) and erbium (Er) addition on microstructure, mechanical properties and thermal expansion of an AA4032 alloy at room and elevated temperatures. Metallographic examination of samples was carried out to characterize the eutectic refinement, primary Si particles and second phase formation at different levels of Cu and Er additions. The results revealed that the amount of primary Si particles increased with increasing Cu addition from 1% to 3.5%. This indicated that Cu addition shifted the eutectic point in the alloy system. However, the Er addition resulted in complete elimination of primary Si particles and refinement of eutectic silicon phases. These results were supported by Thermo-Calc calculations. With increasing Cu and Er concentration to 3.5% and 0.4%, respectively, the hardness increased from 116 HB to 144 HB. The ultimate tensile strength (UTS), yield strength (YS) and elongation (El) were investigated at both room and elevated temperatures. At room temperature, the UTS of these alloys were enhanced with Cu and Er alloying from 279 MPa to 312 MPa. At 350 °C, the UTS was improved to 117 MPa while El was maintained at about 22%. This indicated that Er addition was effective in optimizing the high-temperature properties. The tensile fracture surfaces of the specimens showed that the main failure mechanism was predominantly due to the cracking of primary Si particles in the Al matrix, resulting in the brittle fracture of the alloys without Er. The fracture surface of the samples with Er addition displayed the path through the refined eutectic phase in the ductile fracture mode. The coefficient of linear thermal expansion (CTE) decreased to about 18.3 × 10−6 K−1 at high operating temperature (100–350 °C) for the Er containing alloy. Therefore, this study suggests that the combination of Cu and Er additions in an AA4032 alloy controls the beneficial microstructure in terms of primary Si particles, the refined eutectic Si phase and secondary phases in the Al matrix, which improves mechanical and thermal performances. The low coefficient of linear thermal expansion (CTE) of this alloy makes it suitable for elevated temperature applications

Characterization of the anodic film and corrosion resistance of an A535 aluminum alloy after intermetallics removal by different etching time

The objective of this study was to improve the corrosion resistance of an A535 alloy by removing intermetallics on the alloy surface by alkaline etching to improve the morphologies and properties of the anodic film that was sealed with different sealants. It was found that alkaline etching for 4 min was suitable for dissolving intermetallic particles and simultaneously providing sufficient roughness for the adhesion of an oxide film to the Al matrix. The effect of alkaline etching revealed that a decrease in the intermetallic fraction from 21% to 16% after etching for 2 and 4 min, respectively, corresponded to the increase in the surface roughness, thickness, and consistency of the anodic film. It was also demonstrated that the surface morphology of the anodic films after stearic acid sealing was more uniform and compact than that after nickel fluoride sealing. The electrochemical polarization curves and salt spray test proved that the alloy etched for 4 min and sealed with stearic acid had better corrosion resistance as compared with the aluminum alloy sealed with nickel fluoride