INVESTIGATION OF BEHAVIOUR OF B IN Ni_3AI ALLOYS BY POSITRON ANNIHILATION TECHNIQUE
用正电子湮没技术研究硼在Ni3Al中的存在形式

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.