The influence of nano/micro sample size on the strain-rate sensitivity of plastic flow in tungsten
The influence of nano/micro sample size on the strain-rate sensitivity of plastic flow in tungsten
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DOI：
10.1016/j.ijplas.2020.102854
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发表时间：
2021
影响因子：
9.8
通讯作者：
Pratyush Srivastava;K. Jiang;Yinan Cui;Edgar Olivera;N. Ghoniem;V. Gupta
中科院分区：
文献类型：
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作者：
Pratyush Srivastava;K. Jiang;Yinan Cui;Edgar Olivera;N. Ghoniem;V. Gupta
以螺位错运动为主的体心立方金属的塑性流动特性普遍表现出较强的应变率依赖性。对直径在100~2000 nm范围内的钨(W)单晶纳米和微柱进行了原位扫描电子显微镜压缩实验。我们证明，通过减小样本量，塑性流动的应变率敏感性降低，不仅包括屈服强度，还包括应变突发统计。结果表明，流动应力的应变率敏感性随样本量d为d0而变化。67.对应变爆发尺寸的统计分析表明，微米尺寸的柱子在较高的应变率下具有较低的指数截断幂定律标度。纳米尺寸的柱子(<；500 nm)显示出接近普遍的标度指数1.50±0。07在所有施加的应变率下。应变硬化率和变形形态对应变率不是很敏感。这种外柱样品尺寸效应进一步与纳米晶W的内部晶粒度进行比较，以便通过调整特征长度尺度(外部或晶粒度)来指导新材料的设计
The plastic flow characteristics of body centered cubic metals, which is dominated by the motion of screw dislocations, generally exhibits strong strain rate dependence. In-situ scanning electron microscopy compression tests are performed on tungsten (W) single crystal nano and micro pillars, with diameters in the range 100–2000 nm. We demonstrate here that by reducing sample size, the strain rate sensitivity of plastic flow, including not only the yield strength but also the strain burst statistics, is reduced. It is found that the strain rate sensitivity of the flow stress scales with the sample size d as d 0. 67. Statistical analysis of the strain burst size displays truncated power law scaling with a lower exponent at higher strain rate for micron size pillars. Nano size pillars (< 500 nm) show near universal scaling exponent of 1. 50±0. 07 at all applied strain rates. The strain hardening rate and deformation morphology are found not to be very sensitive to the strain rate. This external pillar sample size effect is further compared with the internal grain size in nanocrystalline W in order to guide the design of new materials by tuning the characteristic length scale (external or grain size)