Investigation of residual stress formation mechanism with water jet strengthening of CoCrFeNiAlx high-entropy alloy

Abstract

This study investigates the strengthening mechanism of water jet (WJ) on the high-entropy alloy CoCrFeNiAlx (x = 0, 0.6, 1). Finite element simulation analysis was conducted to examine the changes in residual stress, surface roughness, and stress triaxiality of high-entropy alloys under different jet velocities and Al contents. Subsequently, an experimental validation of surface roughness was performed using the Al1 high-entropy alloy. The results reveal that the residual compressive stress and maximum residual compressive stress on the high-entropy alloy's surface increase with the jet velocity, irrespective of the Al content. However, the depth of the maximum residual compressive stress decreases as the Al content increases. At a jet velocity of 280 mm/s, the residual compressive stress on the surface of the Al1 high-entropy alloy surpasses that of the Al0.6 high-entropy alloy. Specifically, the residual compressive stress on the surface of the Al1 high-entropy alloy is approximately 265 MPa, which is significantly higher than the value of 9 MPa for the Al0.6 high-entropy alloy. When the jet velocity reaches 300 mm/s, the surface residual compressive stress of the high-entropy alloys shows a positive correlation with the Al content. The residual compressive stress on the surface of the Al1 high-entropy alloy is about 1.89 times and 1.23 times that of the Al0 and Al0.6 high-entropy alloys, respectively. As the jet velocity continues to increase to 320 mm/s, the maximum residual compressive stress of the high-entropy alloys follows the order: Al0.6 > Al0 > Al1. The maximum residual compressive stress of the Al0.6 high-entropy alloy measures approximately 477 MPa, which is approximately 82 MPa higher than that of the Al0 high-entropy alloy. Subsequently, at a jet velocity of 340 mm/s, the Al0.6 high-entropy alloy exhibits the highest maximum residual compressive stress, reaching a value of 650 MPa.Additionally, a negative correlation between surface roughness and jet velocity is observed. Moreover, an increase in Al content within the high-entropy alloys significantly reduces surface roughness under the same jet velocity impact.