摘要
利用正电子湮没技术 (PAT)测量了不同化学计量比二元Ni3Al合金及不同Zr含量Ni3Al合金的正电子寿命谱 ,并估算了合金基体和晶界缺陷处的自由电子密度 .结果表明 ,二元Ni77Al2 3合金的基体和缺陷态的自由电子密度都比二元Ni74 Al2 6 合金的高 .Ni3Al合金晶界缺陷处开空间大于Ni空位或Al空位的开空间 ,晶界缺陷处的自由电子密度很低 ,金属键合力很弱 .过化学计量比Ni74 Al2 6 合金的晶界缺陷开空间比亚化学计量比Ni77Al2 3合金的大 ,晶界结合力更弱 .这是Ni74 Al2 6 合金更脆的原因 .在Ni3Al合金中加入Zr,增加了合金中的金属键成分 ,使基体中的自由电子密度增加 ,增强了基体金属键合力 ,同时降低了合金的有序度 ,使合金晶界容易弛豫 ,晶界缺陷的开空间变小 .另外 ,Zr原子偏聚到晶界 ,增加了晶界处的自由电子密度 ,同时引起晶界处Al贫化 ,减少了强共价性Ni—Al和Al—Al键 ,使晶界更易于变形 ,有利于提高合金的塑性 .
Positron lifetime parameters have been measured by position annihilation technique in binary Ni77Al23, and Ni74Al26 alloys with different Al contents and Ni3Al alloy doped with different amounts of Zr. The density of free electrons in bulk materials and grain boundaries was calculated in this paper. The results show that the density of free electrons in bulk materials and grain boundaries in Ni74Al26 alloy is lower than that in Ni77Al23 alloy. The open volume in grain boundary is larger in Ni74Al26 alloy, and the cohesion of grain boundaries is weaker. When an amount of Zr atoms is added into the Ni3Al alloy, they increase the density of free electrons in the bulk and thus increase the bonding cohesion in the bulk. The other Zr atoms will segregate at grain boundaries and increase their free electron density; this will strengthen the bonding cohesion in grain boundaries. Alloying element Zr is found to be beneficial to reduce the brittleness of Ni3Al alloy with different Al contents.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2005年第4期1868-1873,共6页
Acta Physica Sinica
基金
国家自然科学基金 (批准号 :5 9895 15 2 )资助的课题~~
关键词
镍铝合金
微观机制
自由电子密度
有序度
Ni3Al alloy
micro-mechanism
density of free electron
ductlization
