关于铱微柱的应变突变和应变速率敏感性问题研究

Strain burst and strain rate sensitivity of iridium micro-pillars

摘要:

以聚焦离子束( FIB )制备的直径在1000 nm至7400 nm范围内的< 110 >取向铱单晶柱为材料，进行了单轴压缩试验。实验在纳米机械仪器Sementort中进行，结果表明，单晶柱的屈服强度与直径有显著关系，而与FIB制备无关。单晶柱的微压缩实验与整体铱在单轴压缩试验中的力学行为不同，微纳米尺度的流动应力随着柱直径的减小而增加，即尺寸效应。此外，塑性变形过程有明显的突变和大应变，重点研究了单轴压缩下铱单晶柱的应变突变的速度和应变敏感性问题。结果表明，压缩位移量随着持续时间和立柱直径的增加而增加，同时指出了应变敏感性( SRS )指数m，其值随着柱直径的减小而增加。

Abstract:

The current study presents a uniaxial compression testing of <110>-oriented single-crystalline Iridium micropillars with diameters ranging from 1000 nm to 7400 nm fabricated by focused-ion-beam (FIB). The tests were performed on a nanomechanical instrument. The results reveal that the yield strength of micropillars follow a power law depending on diameter, as reported in other face-centered cubic (FCC) metals. Unlike the mechanical behavior of bulk Iridium when performing uniaxial compression, the flow stress at micro- and nano-scale is found to increase with a decreasing of micropillar diameter, which is attributed to a size-dependent effect. Moreover, the plastic deformation shows a periodical jerky and strain bursts. This work mainly focused on the rate of strain bursts and the sensitivity of strain rate in Iridium micropillars under uniaxial compression. The experiments also indicate that the displacement jumps increase with the extending of durations and micropillar diameter. In addition, the strain rate sensitivity (SRS) index m increases with a decreasing diameter of Iridium micropillar.