Microstructure and mechanical properties of tantalum after equal channel angular extrusion (ECAE)
Microstructure and mechanical properties of tantalum after equal channel angular extrusion (ECAE)
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DOI：
10.1016/s0921-5093(03)00305-8
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发表时间：
2003-10
期刊：
影响因子：
6.4
通讯作者：
Q. Wei;T. Jiao;S. Mathaudhu;E. Ma;K. Hartwig;K. Ramesh
中科院分区：
文献类型：
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作者：
Q. Wei;T. Jiao;S. Mathaudhu;E. Ma;K. Hartwig;K. Ramesh
研究了等通道转角挤压（ECAE）钽的显微组织和力学性能.在准静态载荷和动态载荷下测量机械性能（在后一种情况下，采用压缩Kolsky杆技术以获得103 s-1的应变率）。结果表明，在室温下，采用C路线进行4道次ECAE，其等效应变为4.64，在准静态载荷下使Ta的强度提高2-3倍，在动态载荷下提高1.5倍以上。在准静态载荷下，ECAE处理的样品表现出几乎完美的弹性塑性行为;在动态载荷下，观察到轻微的软化，可能是由于绝热加热。结果表明，ECAE降低了应变速率敏感性。未处理的Ta和ECAE处理的Ta之间的X射线衍射（XRD）的比较表明ECAE处理的样品中XRD峰的显著加宽。透射电子显微镜揭示了纹理，细长的子结构，平均尺寸约为200 nm，和子结构由小角度晶界分开。这项工作显示了利用剧烈塑性变形生产超细晶甚至纳米结构的高熔点难熔金属的潜力。在高应变速率下观察到表明剪切局部化趋势增加的迹象。
We have investigated the microstructure and mechanical properties of equal channel angular extruded (ECAE) Ta. Mechanical properties were measured both under quasi-static loading and dynamic loading (in the latter case, the compression Kolsky bar technique was employed to attain strain rates of ∼103s−1). It is shown that four passes of ECAE with route C at room temperature, which results in an equivalent strain of ∼4.64, increases the strength of Ta by a factor of 2–3 under quasi-static loading, and by a factor of more than 1.5 under dynamic loading. Under quasi-static loading, the ECAE processed samples exhibit almost elastic-perfect plastic behavior; under dynamic loading, slight softening is observed, presumably due to adiabatic heating. It is found that ECAE decreases the strain rate sensitivity. Comparison of the X-ray diffraction (XRD) between the un-processed and ECAE processed Ta indicates significant broadening of the XRD peaks in the ECAE processed sample. Transmission electron microscopy reveals textured, elongated substructures with an average size of about 200 nm, and the substructures are separated by small angle grain boundaries. This work shows the potential for the production of ultra-fine grained or even nano-structured refractory metals with high melting points by using severe plastic deformation. Signs indicating increased shear localization tendancy were observed at high strain rates.