纳米压痕条件下 MgB2 超导块材的压入力学行为研究

本文采用纳米压痕技术对固相烧结法制备的 MgB2 超导块材进行压入力学实验, 对不同压深的载荷-位移曲线和纳米压痕数据的再现性进行了分析, 实验数据使用 Oliver-Pharr 方法计算得出 MgB2 的硬度值, 借助经验方程拟合纳米压痕蠕变曲线求得蠕变速率敏感指数(m ) . 结果表明, 微观结构不均匀性会对材料在压头压入过程中抵抗外力作用时产生影响, 使压痕数据再现性变差; MgB2 的硬度表现出尺寸效应, 即随着压入深度的增加硬度逐渐下降;m 值随压入深度增加而增加是位错滑移速度加快的结果.

Mechanical Behavior of MgB2 Superconducting Bulk under Nano-indentation

In this paper, nano indentation technology was used to conduct the mechanical experiments on MgB2 superconducting bulk material prepared by solid phase sintering. The reproducibility of load-displacement curves and nano-indentation data at different depths was analyzed. The hardness value of MgB2 was calculated by Oliver-Pharr method, and the creep rate sensitivity index (m) was obtained by fitting the creep curve of nano-indentation with empirical equation. The results show that the inhomogeneity of microstructure will affect the resistance of material to external force during the process of indenting the head, and the reproduction of the indentation data will be poor. The hardness of MgB2 shows size effect, that is, the hardness decreases gradually with the increase of indentation depth. The increase of m value with the increase of insertion depth is the result of the acceleration of dislocation slip velocity.