Dynamic-coarsening behavior of an α/β titanium alloy
Dynamic-coarsening behavior of an α/β titanium alloy
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DOI：
10.1007/s11661-006-1091-x
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发表时间：
2006-04
期刊：
影响因子：
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通讯作者：
S. Semiatin;M. Corbett;P. N. Fagin;G. Salishchev;C. Lee
中科院分区：
文献类型：
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作者：
S. Semiatin;M. Corbett;P. N. Fagin;G. Salishchev;C. Lee
通过对超细晶（UFG）坯料圆柱形试样的等温热压缩试验，研究了具有等轴α组织的Ti-6Al-4V合金的动态粗化行为。压缩实验在900和955 °C下进行，应变速率在10 - 4和1 s-1之间，施加的真实应变在0和1.4之间。变形后，定量金相显示在低应变速率（10− 4和10−3s−1）下初生α粒子明显粗化。动力学粗化速率遵循n-时间动力学，其中n在2 ~ 3之间，或介于体扩散和界面反应之间。然而，对理论粗化率的温度和应变率依赖性的研究强烈表明，体扩散（其中n =3）更重要。动态粗化行为也被解释在所观察到的塑性流动行为的上下文中。在低应变率下，高值的应变率敏感性（m>0.5）和对数应力-对数应变率图的整体形状表明，大部分施加的应变是由晶界滑动（gbs）和只有少量通过位错滑移/攀移过程。此外，对伴随动态粗化的流动硬化的分析表明，流动应力与α颗粒尺寸近似线性变化，从而为基于颗粒-地幔区域位错活动的gbs调节模型提供了支持。
The dynamic-coarsening behavior of Ti-6Al-4V with an equiaxed α microstructure was established via isothermal hot-compression testing of cylindrical samples cut from an ultra-fine-grain-size (UFG) billet. Compression experiments were conducted at 900 and 955 °C, strain rates between 10−4and 1 s−1, and imposed true strains between 0 and 1.4. Following deformation, quantitative metallography revealed marked coarsening of the primary α particles at low strain rates (10−4and 10−3s−1). The dynamic-coarsening rate followed rnvstime kinetics, in which n was between 2 and 3, or behavior between those of bulk-diffusion and interface-reaction controlled. An examination of the temperature and strain-rate dependence of theoretical coarsening rates, however, strongly suggested that bulk diffusion (withn=3) was more important. The dynamic-coarsening behavior was also interpreted in the context of the observed plastic-flow behavior. At low strain rates, high values of the strain-rate sensitivity (m>0.5) and the overall shape of log stress-log strain rate plots indicated that the majority of the imposed strain was accommodated by grain-boundary sliding (gbs) and only a small amount via dislocation glide/climb processes. In addition, an analysis of the flow hardening that accompanied dynamic coarsening indicated that the flow stress varied approximately linearly with the α particle size, thus providing support for models based on gbs accommodation by dislocation activity in grain-mantle regions.