Microstructure and mechanical properties of AlMo0.5NbTa0.5TiZr refractory high-entropy alloys fabricated by laser melting deposition

Abstract

The low-density refractory high-entropy alloy AlMo_0.5NbTa_0.5TiZr exhibits excellent high-temperature strength, high-temperature creep resistance, and high-temperature corrosion resistance, making it an ideal material for high-temperature structural applications. AlMo_0.5NbTa_0.5TiZr was formed using electromagnetic induction heating-assisted laser melting deposition (LMD). The influence of laser process parameters on the dendritic morphology of AlMo_0.5NbTa_0.5TiZr was analyzed for the first time, especially the effect of laser power on the diffusion behavior of elements. The mechanism of how elemental diffusion affects the microstructure and mechanical properties was also revealed. The results indicated that at higher laser power, coarse dendritic arms developed within the AlMo_0.5NbTa_0.5TiZr specimens. The dendritic region was enriched with the high melting point Mo-Nb-Ta BCC-1 phase, while the inter-dendritic region was primarily enriched with the low melting point Al-Zr-Ti BCC-2 phase. The increase in laser power led to a significant rise in the Al-Zr enriched Al₃Zr₄ phase. Compared to traditional vacuum arc melting method, AlMo_0.5NbTa_0.5TiZr formed by LMD exhibited a finer grain structure and superior mechanical properties. At a laser power of 1600 W, the average hardness and ultimate compressive strength of the LMD-formed AlMo_0.5NbTa_00.5TiZr specimens reached their maximum values, with the highest average hardness of 660 HV and the ultimate compressive strength of 2012 MPa. This study offers valuable insights into the application of LMD technology for processing novel low-density refractory high-entropy alloys, fostering the future development and application of innovative RHEAs in high-performance fields such as aerospace and energy.