TiAl金属间化合物缺口断裂性能

 TiAl合金作为准脆性材料,在其服役过程中由于缺口的存在使得断裂对缺口非常敏感,严重降低了其使用性能,因此需要研究TiAl合金在缺口作用下的断裂性能。采用带缺口的组合拉伸试样研究了温度和拉伸速率对具有近全片层组织Ti-48Al-2Cr-2Nb合金缺口断裂性能的影响。结果表明,室温下TiAl合金对缺口非常敏感,随着温度的升高,TiAl合金对缺口敏感性降低,当温度为800 ℃时,TiAl合金对缺口不敏感。TiAl合金在低温区塑性变形是通过位错滑移和变形孪晶引起的,高温下是由扩散控制的位错攀移作用引起的。研究还表明,200 ℃下拉伸速率较低时TiAl合金对缺口不敏感,当拉伸速率增加到较高时,TiAl合金对缺口很敏感。

Notch Fracture Properties of TiAl Intermetallic Compounds

As a quaisi-brittle material, TiAl alloys are very sensitive to notches since their existence may cause fracture which may reduce seriously the service performance of the alloy. Therefore it is necessary to study the fracture properties of TiAl alloys with notches. In this article, a study is conducted on the influence of temperature and tensile rate on the notch fracture properties of Ti-48Al-2Cr-2Nb with near full lamellar microstructures using the combined tensile specimens with notches. The study indicates that TiAl alloys possess notch sensitivity at room temperatures, but that the notch sensitivity of TiAl alloys is reduced at higher temperatures. When the temperature reaches 800 ℃, the alloys exhibit little sensitivity to notches. The plastic deformation of TiAl alloys may be caused by dislocation sliding and mechanical twinning at lower temperatures, while at higher temperatures it may be caused by dislocation climbing controlled by diffusion. The study also indicates that TiAl alloys possess no notch sensitivity at lower tensile rates at 200 ℃, while they become sensitive as the tensile rate increases.