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测量了TiAl,Ti50 Al4 8Zr2 和Ti50 Al4 8Nb2 的正电子寿命谱 ,并利用正电子寿命参数分别计算了合金基体和缺陷态的自由电子密度。TiAl合金基体的自由电子密度比金属Ti和金属Al基体的低 ,当Ti和Al组成TiAl合金时 ,Ti原子和Al原子的部分价电子被局域化 ,TiAl合金中金属键和共价键共存。TiAl合金晶界缺陷的开空间较大 ,晶界缺陷处的自由电子密度较低 ,金属键结合力较弱 ,材料易发生沿晶脆断。在TiAl合金中分别加入Nb和Zr元素 ,合金基体和晶界的自由电子密度升高 ,有利于抑制合金解理断裂和沿晶脆断
The positron lifetime spectra of TiAl, Ti50Al4 8Zr2 and Ti50Al4 8Nb2 were measured, and the free electron density of the matrix and the defect state of the alloy was calculated by positron lifetime parameters. The free electron density of TiAl alloy matrix is lower than that of Ti metal and Al matrix. When Ti and Al form TiAl alloy, the partial valence electrons of Ti atom and Al atom are localized, and the coexistence of metal bond and covalent bond in TiAl alloy . TiAl alloy grain boundary defects larger open space, free electron density at the grain boundary defects lower metal bond strength is weak, the material prone to brittle fracture along the crystal. Adding Nb and Zr into TiAl alloy respectively increases the free electron density of the alloy matrix and the grain boundary, which helps to suppress the cleavage of the alloy and the brittle fracture along the crystal