Influence of energy area densities on microstructure evolution and properties of laser direct energy deposited Ni-Co-Mn-Al-Y magnetic shape memory alloy

Abstract

A novel Ni-Co-Mn-Al-Y magnetic shape memory alloy powder was prepared by the vacuum induction melting gas atomization method, and Ni-Co-Mn-Al-Y alloy samples were prepared by laser directed energy deposition (LDED) technique under different energy area densities and subsequent heat treatment. The effects of energy area densities and heat treatment on the grain size, microstructure, phase transformation, compressive strength, and elastocaloric response of the Ni-Co-Mn-Al-Y alloy samples prepared via LDED were clarified. The results showed that the characteristics of the prepared Ni-Co-Mn-Al-Y alloy powder met the requirements of LDED technology and the powder exhibited good laser printability. The microstructure of the samples before and after heat treatment was composed of martensite, austenite, and γ phase. The optimized energy area density sample of 150 J/mm 2 demonstrated a good comprehensive performance with a compressive strength of 1241 MPa and an adiabatic temperature change of –1.9 K. This work can provide a useful reference for preparing high-performance magnetic shape memory alloys by LDED. • A new Ni-Co-Mn-Al-Y alloy powder suitable for LDED was successfully prepared by the VIGA method. • The influence of energy area densities and heat treatment on the microstructure evolution of the prepared alloy was clarified. • The abnormal grain growth was related to the evolution of γ phase and subgrain boundaries during heat treatment. • The alloy with higher compressive strength and better adiabatic temperature change was successfully prepared.