Influence of annealing temperatures on the microstructure and deformation behavior of a CrCoNi based medium-entropy alloy

The pursuit of strong and ductile synergy is a key objective in the development of metals and alloys. Medium entropy alloys (MEAs) have emerged as a highly promising structural material, with potential applications in high-speed trains, aerospace, and defense fields. This study systematically investigates the effect of annealing temperature on the mechanical properties of a CrCoNi based MEA, namely (CrCoNi)97Al1Ti2 MEA. The (CrCoNi)97Al1Ti2 MEA was fabricated by cold rolling reduction of 40% and sub-sequently annealed at 820 & DEG;C for 1 h to achieve a heterogeneous structure that exhibits an excellent combination of strength and plasticity. Scanning electron microscopy and transmission electron microscopy were used to characterize the samples before and after tensile deformation, and to reveal the underlying deformation mechanisms. The results show that annealing at 820 & DEG;C for 1 h introduces a large number of precipitation phases, which are not observed at other annealing temperatures. During plastic deformation, the fine recrystallized grains contribute to the good ductility of the (CrCoNi)97Al1Ti2 MEA, while de-formation twinning and dislocation densities enable it to maintain good strength. The precipitation phase formed by annealing at 820 & DEG;C also significantly improves the strength of the (CrCoNi)97Al1Ti2 MEA. Overall, this study provides insights into the mechanical properties of (CrCoNi)97Al1Ti2 MEA, and highlights the importance of annealing temperature in achieving an optimal combination of strength and plasticity. The findings of this study have important implications for the design and development of MEAs for various applications in structural engineering.& COPY; 2023 Elsevier B.V. All rights reserved.