Open AccessA MICROMECHANISM FOR B IMPROVING THE MECHANICAL PROPERTIES OF MONO- AND POLYCRYSTALLINE Ni3Al ALLOYS
Author(s) -
Wen Deng,
Xiong Liangyue,
Long Qiwei,
Shuhe Wang,
Guo Jianting
Publication year - 1994
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.43.154
Subject(s) - materials science , crystallite , valence electron , grain boundary , electron , cohesion (chemistry) , valence (chemistry) , alloy , covalent bond , atomic physics , condensed matter physics , chemical physics , crystallography , metallurgy , microstructure , chemistry , physics , organic chemistry , quantum mechanics
The microdefects and electronic structure have been studied by measuring the positron lifetime spectra of mono- and polycrystalline Ni3Al alloys with B content ranging from 0.00 to 2.22at%The experimental results show that the opening space of the defect on grain boundary is larger than that of a monovacancy in polycry-stalline Ni3Al alloy. More valence electrons participate in Ni-Ni and Ni-Al bondings in bulk corresponding to stronger cohesion, while less valence electrons parti-cipate in those on grain boundaries corresponding to weaker cohesion. When B atoms segregate to defects, they form strong covalent bondings with Ni and A1 atoms and strengthen the bonding cohesion in those locations. The interaction of B atoms which occupy interstitial siteswith Ni and Al atoms in bulk leads to the increase of the density of valence electrons, thus increases the bonding cohesion in the bulk.