51.1Zr-40.2Ti-4.5Al-4.2V合金拉伸变形过程中的组织演变和力学性能研究

A study on microstructure evolution and mechanical properties of 51.1Zr-40.2Ti-4.5Al-4.2V during tensile deformation

摘要:

本文主要研究了51.1Zr-40.2Ti-4.5Al-4.2V合金室温拉伸变形过程中的组织演变和力学性能变化。研究表明，室温拉伸变形过程中合金发生从β相到α"相的转变，α"相的体积分数随拉伸速率的增加而减小。应力诱发α"马氏体相变对合金的力学行为有明显的影响。在拉伸速率为0.3 mm/min时，触发应力（TS），极限拉伸强度（UTS），延伸率（EL）和弹性模量（EM）分别为770.06 MPa，1168.60 MPa，14.96%和64 GPa。TS和EM随拉伸速率的增加而增加，而UTS和EL则降低。加工硬化率与真应变的关系曲线呈现出3个不同的阶段，应力诱发α"马氏体相变主要影响加工硬化率曲线的第2阶段。在给定应变条件下，第2阶段的加工硬化率随拉伸速率的增加逐渐降低。拉伸速率为0.3 mm/min时，合金的断口形貌是由大量韧窝以及少量准解理面组成的，合金发生塑性断裂，随着拉伸速率的增加，合金断裂方式由塑性断裂变为脆性断裂。这主要与应力诱发α"马氏体相含量随拉伸速率的增加而降低有关。

Abstract:

The microstructure evolution and mechanical properties of 51.1Zr-40.2Ti-4.5Al-4.2V alloy during tensile deformation at room temperature were studied. The results show that the phase transformation from β to α" phase were observed in the process of tensile deformation at room temperature, and the volume fraction of the α" phase decreases with the increase of the tensile rate. The existence of the α" phase has an obvious effect on the mechanical properties of the alloy. At the tensile rate of 0.3 mm/min, the trigger stress (TS), ultimate tensile strength (UTS), elongation (EL) and elastic modulus (EM) were 770.06 MPa, 1168.60 MPa, 14.96% and 64 GPa, respectively. TS and EM increased with the increase of tensile rate, while UTS and EL decreased. Three different stages were presented in the curve of work hardening rate. Especially, the second stage was obviously affected by the α" phase. At a given strain, the work hardening rate at the second stage is gradually decreased with increasing tensile rate. When the tensile rate was 0.3 mm/min, the fracture morphology of the alloy was composed of a large number of dimples and a small number of quasi-cleavage planes, which show a typical feature of plastic fracture. With the increase of the tensile rate, the fracture mode of the alloy changed from plastic fracture to brittle fracture. This is mainly due to that the volume fraction of the α" phase decreases with the increase of the tensile rate.