NiAl中空位的回复行为

Recovery behavior of vacancies in NiAl

用正电子湮没技术研究了金属间化合物ＮｉＡｌ的淬火缺陷和电子辐照缺陷的回复行为。发现高温淬火试样在２８０℃左右和５００℃左右有两个明显的回复阶段。进一步采用嵌入原子法类型的势函数．角分子动力学方法对ＮｉＡｌ中的单、双空位进行了计算机模拟研究．计算了空位三种迁移机制的激活能。结果表明，空位六步跳跃循环运动是能量上有利的迁移机制。实验和计算结果的对照表明：低温回复是由于Ａｌ空位的退火，而高温回复对应于Ｎｉ空位的退火．并且ＮｉＡｌ有序合金中的扩散主要是由于空位的运动而引起的。

The recovery behavior of quenched-in or radiation-induced defects in the intermetallic compound NiAl has been studied by positron annihilation techniques.Two distinct recovery stages in NiAl samples quenched from temperature above 950℃ were found by Doppler broadening measurements;one at around 280℃and the other at around 500℃.The molecular dynamics was then further used to simulate mono-vacancies and divacancies in the NiAl of stoichiometric composition with'embedded atom method'(EAM) potentials. The vacancy ingration energies for three different mechanisms were calculated. The calculations indicated that the energetically favorable mechanism for vacancy migration was six-jump vacancy cycle.A comparison with the experiments showed that Al vacancies annealed out at the～280℃recovery stage while Ni vacancies at the～500℃ stage, and the vast majority of diffusion events in the ordered NiAl alloy were mainly attributed to the motion of vacancies.