Microstructure and nanoindentation creep behavior of NiAlCrFeMo high-entropy alloy

Abstract

This study provides a systematic investigation of the microstructure, mechanical properties, and creep behavior of NiAlCrFeMo high-entropy alloys (HEAs) in both as-cast and rotary swaging (RS) conditions. The phase structure, composition, and distribution of the alloys in both states were characterized using various microstructural characterization techniques. Both as-cast and RS samples consist of γ/γ' phases and B2 phases, although the RS samples contain small amounts of nano-sized α-Cr precipitates. The hardness, elastic modulus, and yield strength of the two HEA states were evaluated using continuous stiffness measurement (CSM) techniques and room-temperature compression tests, with maximum hardness and yield strength values of approximately 4.93 GPa and 719 MPa, respectively. Nanoindentation creep experiments were conducted to study the creep behavior under different strain rates. The results indicate that the creep strain rate sensitivity and activation volume of the as-cast samples are dependent on the loading strain rate (${\dot{\epsilon }}_L$${\dot{\epsilon }}_L$), while the RS treatment effectively suppresses this phenomenon. In comparison with conventional alloys, the NiAlCrFeMo HEA exhibits lower strain rate sensitivity, suggesting excellent creep resistance. This performance can be primarily attributed to the interaction between the alloy's geometrically necessary dislocation (GND) density and the precipitate phase.