纳米尺寸下铱单晶微柱的力学行为

Mechanical Properties of Single Crystal Iridium Micro-pillars to Nanometer Scale

本文采用聚焦离子束法(Focused Ion Beam,FIB)对<110>取向铱(Ir)单晶进行切割,加工出直径为400~3000nm的微柱样品,随后在带有平压头的纳米压痕仪上进行压缩试验来研究其力学行为。Ir单晶微柱压缩的工程应力-应变曲线表明,流变应力随着微柱直径的减小而增加,即存在"尺度效应",且流变应力与微柱直径符合幂律关系,同时工程应力-应变曲线上出现了离散的"应变陡增",利用"位错匮乏"机制能够对这种现象进行较好的解释。微柱压缩变形后的扫描电镜(SEM)图像表明微柱的滑移方式为多滑移,并且滑移与微柱直径相关。

Micron-sized 110-oriented single-crystal iridium is cut by focused ion beam（FIB）into pillars with diameters ranging from 400 nm to 3000 nm.And the sample is characterized by microcompression tests with a a nanoindentation instrument with flat punch to study their mechanical behavior.Measured stressstrain curves show that the flow stress of micropillars increases with decreasing diameters under uniaxial compression,that is＂size effect＂,and the relationship between flow stress and diameters can be described by a power-law.Moreover,the discrete strain bursts were observed in stress-strain curves,which can be explained by the mechanism of dislocation starvation.SEM images of deformed iridium single crystal micro-pillars reveal that they are deformed in multiple slip condition,and the slip is relevant to the diameter.