研究了尺寸为0.3~2.0 μm的Ti-10V-2Fe-3Al (Ti1023)微柱沿[011]位向压缩的变形行为及微观机制. 结果表明: Ti1023 微柱沿[011]位向压缩的塑性变形阶段应力-应变曲线光滑, 表现出持续加工硬化, 无应变突发现象. 微柱屈服强度(σ0.2)随试样尺寸(d)的减小而增加, 其关系为: σ0.2∝d -0.18. 微柱塑性变形以{112}<111>滑移主导, 应变量超过10%时产生应力诱发马氏体(α″), 应力诱发马氏体相变发生时的应力(σcm)亦随d的减小而增加, 其关系为: σcm∝d -0.28. 在均匀塑性变形阶段, 应变硬化指数(n)随尺寸的减小而增加. 采用TEM观察了变形前后微观组织形貌, 表明Ti1023微柱沿[011]位向压缩时表现出来的持续应变硬化归因于晶体中纳米尺度ω相和α″对位错滑移的阻碍作用.
Ti and its alloys have potential application in micro-electromechanical systems (MEMS) for its excellent mechanical properties. The strength of micro- and nano-scale Ti and its alloys has been proven significantly increased as the sample size decreased, which is known as the "size effect", when dislocation and twinning are dominant plastic deformation modes. Martensitic transformation is an important plastic deformation mode in the Ti alloys. However, there is a limited research on the martensitic transformation in small-scale. Therefore, the study on mechanical behavior and deformation mechanism of [011]-oriented Ti-10V-2Fe-3Al (Ti1023) single crystal micropillars in a size range of 0.3~2.0 μm were investigated under uniaxial compression. The results show that Ti1023 micropillars exhibit smooth stress-strain curves in the regime of plastic deformation without a conventional strain burst phenomenon in the submicron pillars. It means continuous plastic strain hardening. The relationship between the yield stress (σ0.2), the stress for stress-induced martensite phase (SIM) transformation (σcm) and the sample size can be expressed in the forms of σ0.2∝d -0.18 and σcm∝d -0.28 , respectively. Strain hardening exponent (n) in creases with decreasing micropillar size. SEM examination together with crystallography analysis show that {112}<111> slip predominates plastic deformation mode in the Ti1023 micropillars. Transmission electron microscopy (TEM) observation of microstructures in the deformed and undeformed micropillars indicate that both nanoscale athermal ω particles and SIM phase α″ impede dislocation movement, and prohibit the formation of tangled dislocations in a collective, avalanche-like way resulting in strain bursts.
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