Influence Mechanism of Gradient Microstructure on the Properties of Ti2AlNb-Based Alloy

Abstract:

Ti₂AlNb-based alloy samples with gradient microstructures were obtained by gradient extrusion at 980 °C. The gradient microstructures of Ti₂AlNb-based alloy samples were characterized by XRD, SEM and TEM, and their properties were studied by nanoindentation and nano-scratch tests. The influence of gradient microstructures on the properties of Ti₂AlNb-based alloy was investigated. The results show that the microstructure in the core of the gradient extruded Ti₂AlNb-based alloy specimen is mainly composed of the coarser B2 phase and the near-equiaxed α₂ phase distributed at the grain boundaries, and the dislocation density is low, which is mainly distributed in the B2 phase and the B2/α₂ phase boundaries. The microstructure in the edge is composed of smaller B2 phases, a large number of rod/slat-like O phases and a small number of equiaxed α₂/O (rim O) phases, and the dislocation density is high, which is mainly distributed at the interface between the slat/equiaxed O phase and the B2 phase, and in the O phase and α₂ phase. The core of the gradient extruded specimen has the lower hardness and better plasticity. The edge has higher hardness under various effects such as O-phase strengthening, fine-grained strengthening and dislocation strengthening, and the wear resistance are significantly improved. The gradient microstructure can confer the good comprehensive service performance of the Ti₂AlNb-based alloy.