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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 annihilation (PAT) was used to measure positron lifetime spectra of binary Ni3Al alloys with different stoichiometric ratios and Ni3Al alloys with different Zr contents, and the free electron density of the alloy matrix and grain boundary defects was estimated. The results show that binary The Ni77Al2 3 alloy has higher free electron density in the matrix and defect states than the binary Ni74Al2 6 alloy.Ni3Al alloy has a larger open space at the grain boundary defects than the Ni vacancies or Al vacancies and the free electron density at the grain boundary defects is very high Low, the bonding strength of metal is weak.The stoichiometric ratio of Ni74Al2 6 alloy grain boundary defect open space than the stoichiometric Ni77Al2 3 alloy large grain boundary bonding strength is weaker .This is Ni74Al2 6 alloy more brittle Addition of Zr to Ni3Al alloy increases the content of metal bonds in the alloy, increases the free electron density in the matrix, strengthens the bond strength of the matrix, decreases the degree of ordering of the alloy, relaxes the grain boundaries of the alloy, In addition, the Zr atoms segregate to the grain boundaries, increasing the free electron density at the grain boundaries, causing the Al depletion at the grain boundaries and reducing the strong covalent Ni-Al and Al- Al key, The grain boundary more easily deformed, help to improve the ductility of the alloy.