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High-entropy alloys (HEAs) have attracted widespread attention from scholars as a new type of material employed in extreme environments. However, as a main kind of HEAs, many face-centered cubic single-phase HEAs are restricted in industrial applications due to their lower yield strength and high cost when containing expensive elements such as Co. In this study, dispersion strengthening by heat treatment was introduced in low-cost Co-free Fe40Mn20Cr20Ni20 HEA to improve its strength, and its high-temperature tensile behavior and constitutive model were studied to explore its potential application at high temperatures. It is found that when subjected to quasi-static room-temperature stretching, the heat-treated sample exhibits a yield strength of 534 MPa and a tensile plasticity of 26.8%. In addition, the tensile behavior of samples after heat treatment was investigated at high temperature (573–873 K) and low strain rate (10−3–10−1 s−1). The results suggest that the yield strength decreases with increasing temperature and decreasing strain rate. Moreover, at 873 K and 10−3 s−1, the electron backscatter diffraction system and x-ray diffraction results of the deformed sample indicate that the softening curve is driven from the recovery of materials. Finally, the flow stress was predicted using the Arrhenius equation and Artificial Neural Network model (ANN), and the two models were assessed using the average absolute relative error and coefficient of correlation (R). The results showed that the ANN had higher accuracy. [ABSTRACT FROM AUTHOR]

The Portevin–Le Chatelier (PLC) effect induced by dynamic strain aging is commonly observed in various alloys. The stress-drop magnitude of serrations and the critical strain at which serrations occur are two pivotal features characterizing serrated flow. This study investigates the temperature (160–460 °C) and strain rate (6 × 10−4 s−1–2 × 10−2 s−1) dependence of the serrated flow behavior in the CoNiV medium-entropy alloy through uniaxial tensile tests. Under the guidance of the mean-field theory, a scale theory has been applied to derive a scale function and scale indices that can be used to predict the distribution of stress drops. A normal PLC behavior of critical strain is fitted using the dislocation pinning model, demonstrating the presence of specific solute atoms conforming to the dislocation pinning model within medium-entropy alloys. [ABSTRACT FROM AUTHOR]