Atomic investigations on the tension-compression asymmetry of Al x FeNiCrCu (x=0.5, 1.0, 1.5, 2.0) high-entropy alloy nanowires

摘要

The tension and compression of high-entropy alloy (HEA) nanowires (NWs) are remarkably asymmetric, but the micro mechanism is still unclear. In this research, the tension-compression asymmetry of Al x FeNiCrCu HEA NWs (x = 0.5, 1.0, 1.5, 2.0) was quantitatively characterized via molecular dynamics simulations, focusing on the influences of the NW diameter, the Al content, the crystalline orientation, and the temperature, which are significant for applying HEAs in nanotechnology. The increased NW diameter improves the energy required for stacking faults nucleating, thus strengthening AlFeNiCrCu HEA NWs. A few twins during stretching weaken the strengthening effects, thereby decreasing the tension-compression asymmetry. The increased Al content raises the tension-compression asymmetry by promoting the face-centered cubic to body-centered cubic phase transition during stretching. The tension along the 001 crystalline orientation is stronger than the compression, while the 110 and 111 crystalline orientations are entirely the opposite, and the tension-compression asymmetry along the 111 crystalline orientation is the minimum. The diversities in the tension-compression asymmetry depend on the deformation mechanism. Compressing along the 001 crystalline orientation and stretching along the 110 crystalline orientation induces twinning. Deformation along the 111 crystalline orientation only leaves stacking faults in the NWs. Therefore, the tension and compression along the 111 crystalline orientation exhibit minimal asymmetry. As the temperature rises, the tension-compression asymmetry along the 001 and 111 crystalline orientations increases, while that along the 110 crystalline orientation decreases.