单晶铱纳米压痕下位错形核与形变研究

Dislocation nucleation and room temperature deformation of single crystal Iridium

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 ?3、1.23 ?3，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，位错间交互作用导致的结果。

Abstract:

The brittle of Ir single crystal in nature has attracted more attention due to the fact that Ir 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 were calculated to be 1.09 ?3、1.23 ?3 for the (100) and (110) planes 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 60.57eV, and the activation radius reaches 1.971nm. In the plastic deformation of Ir single crystal, the deformation dislocation density was found to be the order of 1014m-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 eventually caused by severely dislocation interaction.