Effects of vacuum heat treatment on novel Co-free Al0·9Cr0·8FeMn0·8Ni2.0 eutectic high entropy alloy: Microstructure evolution and mechanical properties

Abstract

This study is dedicated to the development of Co-free eutectic high entropy alloy (EHEA) with potential applications in nuclear power. An Al0·9Cr0·8FeMn0·8Ni2.0 EHEA was initially synthesized and subjected to annealing at varying temperatures to investigate microstructural transformations. In its as-cast state, the alloy displayed dendritic (FCC), sunflower petal-like eutectic (FCC + BCC), and sunflower disc-like matrix (BCC) structures. Following annealing at 600 °C for 2 h, a substantial increase in BCC phase content notably enhanced the alloy's strength. Concurrently, plasticity improved due to grain refinement resulting from recrystallization, yielding a remarkable tensile strength exceeding 1000 MPa and an elongation of 7.3%. At elevated annealing temperatures (700–800 °C), a considerable dissolution of FCC phase occurred, giving rise to the formation of needle-like ordered B2 phase (rich in Al and Ni) precipitates and diminished mechanical properties. The temperature-microstructure-mechanical linkages identified in this investigation provide valuable insights for future research in EHEAs tailored for nuclear applications.