本文用正电子湮没技术(PAT)研究了不同硼含量的单晶和多晶Ni_3Al中硼原子的存在形式。在Ni_3Al合金中加入少量硼(≤1.37％)时,一部分硼原子以间隙方式溶解到基体中,使晶格发生畸变,导致基体中正电子寿命(τ)增长;另一部分硼偏聚到空位型缺陷上,产生“填充效应”,导致平均寿命■和S参数下降。硼量为2.22at.-％时,缺陷态的τ显著增长,■和S参数增大,表明在晶界成晶内析出硼化物,诱发了较多的自由体积较大的缺陷。
The behaviour of B atoms added to mono- and poly-crystalline Ni_3Al alloys has been investigated by positron annihilation technique. If an additive of B less than 1.37 at.-%, some of B atoms solid-dissolved interstitially into matrix and distorted the lattice, thus the lifetime of positron in matrix dilated; the others of them segregated on vacancy-like defects and formed" filling effect", thus the mean lifetime and S parameters decreased. If B added up to 2.22 at.-%, more defects having larger free volume were induced by boride eutectic occurred along grain boundaries and grain interior, thus the positron lifetime in vacancy-like defects, mean lifetime and S parameters increased remarkably.
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