Ti14合金在等温热暴露条件下Ti_(2)Cu相的粗化行为

Coarsening Behavior of TiCu Phase of Ti14 Alloy During Isothermal Thermal Exposure

研究了Ti14合金中Ti_(2)Cu相在500℃等温热暴露下的静态粗化行为,揭示出Ti_(2)Cu相的生长速率和形态变化受扩散机制控制。结果表明:静态粗化过程由快速粗化阶段和稳定粗化阶段组成,其中快速粗化阶段主要由末端迁移机制控制,由于条状Ti_(2)Cu相的末端与长轴方向界面能的差异,溶质原子的扩散过程导致板条状Ti_(2)Cu的粗化和破碎。而稳定粗化阶段主要由Oswald熟化机制控制,随着时间的延长,合金中Ti_(2)Cu析出物的尺寸持续增大,而粗化速率降低。Ti_(2)Cu相的快速粗化会引发第二相的强化,并有效提高快速粗化阶段的可塑性。但是在稳定粗化阶段,由于Ti_(2)Cu相的长大会增加其位错的有效滑移长度,并进一步影响其裂纹形核阻力同时改变界面构型和晶格失配,从而降低Ti14合金的拉伸塑性。

The static coarsening behavior of Ti_(2)Cu phase in Ti14 alloy during long term exposure at 500 ℃ was investigated. The results show that the growth of precipitated phase is controlled by the diffusion mechanism revealed by the morphology variation during thermal exposure. The static coarsening processes are composed of rapid coarsening stage and stable coarsening stage, which are controlled by volume diffusion with LSW model. The rapid coarsening stage is mainly dominated by the terminal migration mechanism, and the stable coarsening stage is proceeded mainly by Oswald ripening mechanism. The rapid coarsening of the Ti_(2)Cu phase initiates the strengthening of the second phase and effectively improves the plasticity in the rapid coarsening stage. But in the stage of stable coarsening, the growth of Ti_(2)Cu phase increases the effective slip length and further affects the crack nucleation resistance, thereby reducing the tensile plasticity of the Ti14 alloy.