梯度组织对Ti2AlNb基合金性能影响机理

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

摘要:

通过在980 ℃对Ti₂AlNb基合金进行梯度挤压获得了具有梯度组织结构的试样。采用XRD、SEM、TEM对Ti₂AlNb基合金的梯度组织进行表征，采用纳米压痕和纳米划痕等试验对其性能进行研究，深入分析了梯度组织对Ti₂AlNb基合金性能的影响。结果表明：梯度挤压Ti₂AlNb基合金试样小变形心部组织主要由较为粗大的B2相及其晶界处分布的近等轴α₂相组成，位错密度较低，主要分布在B2相内部和B2/α₂相界上；大变形边缘组织由更加细小的B2相、大量分布较为均匀的棒/板条状O相和少量等轴α₂/O（rim O）相组成，位错密度较高，主要分布在板条/等轴O相与B2相界面处、O相及α₂相内部。梯度挤压试样心部硬度较低，耐磨性较差，但塑性较好；边缘区域在O相强化、细晶强化和位错强化等多种作用下具有较高的硬度，耐磨性能显著提升。Ti₂AlNb基合金中各相含量及尺寸沿径向呈梯度分布的组织结构可以使其获得良好的综合力学性能。

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.