Structure and mechanical properties of Al–Si–Fe alloys prepared by short-term mechanical alloying and spark plasma sintering

Abstract

Al–10Si–21Fe and Al–20Si–16Fe (wt.%) alloys were prepared by mechanical alloying and subsequent compaction via SPS technology. A heat-treated and artificially aged casting Al–12Si–1Cu–1Mg–1Ni (wt.%) alloy, generally considered to be thermally stable, was used as a reference material. The ultrafine-grained microstructure of compact alloys resulted in excellent mechanical properties, e.g., hardness and compressive strength. Furthermore, the Al–10Si–21Fe alloy exhibited an unexpected yield drop when compressive tested at elevated temperatures. Both tested alloys exhibited high initial hardness reaching almost 400 HV5, exceeding the hardness of the reference alloy by nearly a factor of four. Additionally, even when annealed at 400 °C for 100 h, the change in hardness was negligible. Furthermore, the compact Al–10Si–21Fe and Al–20Si–16Fe alloys exhibited compressive strengths of 1033 MPa and 758 MPa, respectively. The casting alloy exhibited low mechanical properties compared to those of the investigated alloys at laboratory temperature and softened remarkably during annealing, reducing its initial compressive yield strength and compressive strength from 430 MPa and 680 MPa to 180 MPa and 498 MPa, respectively. Moreover, the initial hardness of the casting alloy decreased by 50% to a final value of 63 HV5. In contrast, the investigated compact alloys maintained high compressive strength even after annealing.