Microstructure and mechanical properties of a novel AlSiFeNiMn alloy fabricated by laser powder bed fusion

Abstract

Al-Si alloys fabricated by laser powder bed fusion (LPBF) exhibit excellent comprehensive mechanical properties. However, the application of LPBF-ed Al-Si alloys was limited by their poor high temperature properties. To meet the requirement of automotive and aerospace industries, a novel Al-Si alloy needs to be developed. In this study, a new type of LPBF-ed AlSiFeNiMn alloy was prepared, demonstrating excellent mechanical properties at both room and elevated temperatures. AlSiFeNiMn alloy samples were fabricated by LPBF. The melting channel and cellular structures were characterized. Evenly distributed intermetallic compounds α-Al(FeMn)Si and Al₃Ni were present in the as-built samples, and the accumulation of α-Al(FeMn)Si in secondary cells was analyzed. The superior tensile properties of LPBF-ed AlSiFeNiMn alloy were confirmed (UTS 513 MPa, EI 8 % at 25 °C; UTS 248 MPa, EI 14 % at 300 °C; UTS 153 MPa, EI 15 % at 400 °C). The increase in tensile strength is primarily attributed by the introduction of finely dispersed phases α-Al(FeMn)Si and Al₃Ni, while the grain size of as-built sample shows no obvious refinement compared to those of existing LPBF-ed Al-Si alloys. Intermetallic compounds with excellent thermal stability and hardness effectively prohibit the slide of dislocations at 400 °C, which significantly improve the mechanical properties of the AlSiFeNiMn alloy.