Strategies for optimizing mechanical properties of refractory high entropy alloys induced by solid solution strengthening mechanism

How to optimize the strength-plasticity matching of refractory high entropy alloys (RHEAs) by simple strategies has been widely discussed. Generally, the strengthening mechanism of RHEAs mainly comes from the solid solution strengthening (SSS) caused by atomic radius mismatch and modulus mismatch. However, excessive atomic radius mismatch can increase the distortion energy of the RHEA and decrease its plasticity. Therefore, we propose a strategy to enhance modulus mismatch without altering atomic radius mismatch, thereby improve the strength-plasticity of RHEAs. We selected the ZrTiNb system as the model and increased the modulus mismatch by adding Ta, resulting in a 23.8 % increase in strength and an 82.3 % increase in plasticity. More importantly, the addition of Ta can decrease the diffusion rate of elements within the RHEAs and serve to refine the grains. This provides a significant avenue for developing RHEAs with outstanding properties.