Evolution of 3D interconnected composites of high-entropy TiVNbMoTa alloys and Mg during liquid metal dealloying

Abstract

The high-entropy alloy (HEA) design strategy is effective for ultra-coarsening-resistant 3D interconnected materials developed by liquid metal dealloying (LMD). However, the fundamental understanding of the dealloying mechanism and structural evolution of multi-principal elements 3D structured materials is still missing. In this study, the microstructural evolutions of 3D interconnected HEAs in Mg matrix were investigated using two types of multiphase precursors, namely, arc-melted and homogenized ones. The precursors' microstructure greatly influences dealloying kinetics and dealloying mechanisms what, in its turn, determines the final morphology of the 3D interconnected HEAs in Mg matrix. First, the prior fcc phase was dealloyed faster than any other precursor phases at dealloying temperatures from 600 to 900 °C. Second, the dealloying kinetics was faster along precursor grain boundaries (GB) as compared with grain interior. This led to the formation of a unique layered composite structure due to the inhomogeneous dealloying along the fine lamellars’ GB of the homogenized precursor. Moreover, governing orientation relationship between precursor and dealloying product depends on the LMD conditions, and it significantly affects the 3D interconnected grain structure. The fundamental understanding of the dealloying mechanisms will pave the way for customized morphology design of the 3D interconnected HEAs in metallic matrix with improved thermal stability and physical properties.