Formation of metastable bcc-δ phase and its transformation to fcc-γ in laser powder bed fusion of Fe–Mn–Si shape memory alloy

Abstract The phase transformation behavior from metastable bcc-δ to fcc-γ in Fe–Mn–Si based shape memory alloy processed by laser powder bed fusion was investigated. Primary δ phase formed in this alloy due to the rapid cooling and fast solidification. Bcc-δ to fcc-γ phase transformation occurred when the volumetric energy density was high due to the process-inherent heat treatment effect. Transmission electron microscope studies confirmed Kurdjumov-Sachs orientation relationship between bcc-δ and fcc-γ phases. The analytical results revealed that the phase transformation occurred by a combined displacive-diffusional mechanisms.