(北京有色金属研究总院 有色金属材料制备加工国家重点实验室，北京 100088)
摘 要: 对工业纯钛Gr2的准静态(1×10-3 s-1)和动态(3×103 s-1和6×103 s-1)力学性能曲线进行测量，并通过等温变形曲线计算材料压缩变形时的应变硬化模量。结果表明：塑性应变低于0.2时，动态变形过程的应变硬化模量明显高于准静态变形过程的。通过孪生分数统计和变形组织观察发现，应变速率提高对应变硬化的强化效应源自于塑性变形初期(εp≤0.2)孪晶的大量形成，即孪生强化效应。然而，随着变形的持续进行，孪生强化效应会随着组织中二次孪晶的形成和位错切过孪晶界导致的晶界扭曲而逐渐减弱并消失。位错运动至孪晶界时，受到的阻力以及塞积和切过行为将是影响孪生强化效应的主要因素。
关键字: 纯钛；孪生；高应变速率；应变硬化；临界分切应力
（State Key Laboratory of Non-ferrous Metals and Processing, General Research Institute for Non-ferrous Metals,
Beijing 100088, China）
Abstract:The quasi-static (1×10-3 s-1) and dynamic (3×103 s-1 and 6×103 s-1) mechanical properties curves of commercial pure (CP) titanium Gr2 were obtained, and the strain hardening modulus was derived based on isothermal compression curves. The results show that within plastic strain of 0.2, the strain hardening modulus of dynamic deformation process is evidently higher than that of quasi-static process. The twin fraction measurement and microscopic observation of the deformed structure show that the enhancement of strain hardening in the dynamic process is closely related with the abundance of mechanical twinning. As the material deforms further, second order twinning forms, and twin boundary is distorted by dislocation, which leads to the fact that the twinning strengthen effect becomes weaker, and finally disappears. The interaction between dislocation and twin boundary is the influencing factor of the twinning strength effect.
Key words: pure titanium; twinning; high-strain-rate; strain hardening; critical shear stress
