Microstructure and mechanical properties of Al0.3FeCoCrNi high entropy alloy processed by laser powder bed fusion using FeCoCrNi and Al powder mixture

Abstract

In this work, an Al0.3FeCoCrNi high entropy alloy with high density and good mechanical properties is synthesized by laser powder bed fusion (LPBF) using FeCoCrNi and AlSi10Mg blended powders. The as-built alloy has dual phase microstructure consists of FCC and B2/BCC. B2/BCC phase is formed at the grain boundary as a result of the partial homogenization of elements within each melt pool in the in-situ alloying of mixed powder. Nano oxide particles are also detected, which is inherited from the oxide of the Al powders. The as-built alloy has a strong <001>//BD (Build direction) texture. The dual phase structure Al0.3FeCoCrNi has good mechanical properties, with yield strength of 503 MPa, tensile strength of 685 MPa and elongation of 32%. Microstructural analysis shows that high dislocation density is the main reinforcing factor of the as-built Al0.3FeCoCrNi alloy. After heat treatment at 650 °C for 70 h, the alloy precipitated nano L12 phase inside the grain, (Al, Ni)-rich nano B2 and Cr-rich σ at the grain boundary, and Cr-rich σ in the B2/BCC region. Thus, the strength has been significantly improved, the yield strength has reached 845 MPa, the tensile strength has reached 1084 MPa, and the elongation remains about 14%.