【摘要】 对（100）和（110）不同面的铱单晶进行了纳米压痕实验,拟合计算得到（100）与（110）面上铱单晶位错激活体积分别为1.09×10^-3nm³、1.23×10^-3nm³,证明该实验条件下位错来源于点缺陷的非均质形核;如果位错为均质形核,则位错激活能需达到60.57eV,激活半径达到1.971nm。在对（100）和（110）面的塑性变形中位错密度进行分析时,发现它们变形后位错密度在10¹⁴m^-2左右,没有出现铱单晶变形后位错密度呈指数级增加的情况;金属铱发生脆性断裂或许因为铱中极小的位错激活体积导致铱产生大量的位错源及位错间剧烈的交互作用。更多还原

【Abstract】 The brittleness of Ir single crystal in nature has attracted more attention because it is a fcc metal.In this paper,nanoindentation experiments were performed on the（100）and（110）planes of Ir single crystal.The results show that the dislocation activation volumes of Ir single crystal are calculated to be 1.09×10^-3 nm³ and 1.23×10^-3 nm³ for the（100）and（110）planes,respectively,based on the first pop-in data from load-displacement curves.These results clearly demonstrate that the formation of dislocation is probably nucleated heterogeneously from point-like defects,while for the homogeneous nucleation,the activation energy should reach 60.57 eV,and the activation radius reaches 1.971 nm.In the plastic deformation of Ir single crystal,the deformation dislocation density is found to be the order of 10¹⁴ m^-2,which agrees with the previously reported data,implying that the anomalously high dislocation density does not exist in this nanoindentation experiment.The brittle fracture of Ir in nature may be attributed to the extremely small dislocation activation volume,leading to a large number of dislocation sources and severe dislocation interaction.更多还原