Effect of multi‒directional forging on the evolution of intermetallic precipitates and mechanical properties in novel light refractory high-entropy alloys

Abstract

The mechanical properties of refractory high‒entropy alloys (RHEAs) are influenced by the types and concentrations of the constituent elements and significantly influenced by the precipitation behavior. In this study, the Al₂₀Nb₁₄Ti₃₄Zr₂₉Cr₄ RHEA was designed to investigate the impact of precipitation on its microstructure and properties. The density of the alloy was only 5.53 g/cm³. Significant amounts of the Al₃Zr₅ phase and C14 Laves phase precipitated following prolonged annealing treatment. The evolution of the microstructure of the alloy was investigated through multi‒directional forging at temperatures of 1000 °C and 1200 °C. High‒temperature forging causes the dissolution of the Al₃Zr₅ phase, and greater dissolution occurs at elevated temperatures. Additionally, during high‒temperature forging, dissolution and subsequent reprecipitation of the C14 Laves phase occur. Lower forging temperatures promote increased reprecipitation of the C14 Laves phase. The alloy forged at 1000 °C exhibited an exceptional yield strength of 1870.1 MPa, accompanied by a specific yield strength of 338.2 N∙m/kg and a compressive limit deformation of 20.9 %. This remarkable performance can be attributed to the changes in the shape size and distribution of the precipitated phase during the forging process at 1000 °C, as well as the grain refinement caused by recrystallization. These factors work together to improve the strength and plasticity of the alloy.