Mo,Ta,W在Ni_xAl_(1-x)(x=0.25,0.5,0.75)中的择优占位

Site-preference of Mo/Ta/W alloying additions in Ni_xAl_(1-x)(x=0.25,0.5,0.75)

用多体势结合分子动力学计算了L12型NiAl3,L12型Ni3Al,L10型NiAl和B2型NiAl的晶格常数,结合能以及合金形成热;分析了结构性点缺陷在上述四种合金中的存在形式;在此基础上研究了合金化元素Mo,Ta,W在NixAl1x(x=0.25,0.5,0.75)中的择优占位行为.计算结果表明:对于四种结构的Ni-Al合金,偏离理想化学配比时,主要的结构缺陷形式是反位置;根据占位能最小化,第三组元元素Mo,Ta,W在上述四种Ni-Al中都显著优先占据Al格位.

The characteristic properties including equilibrium lattice constants, elastic constants, cohesive energies and alloy formation energies, of stoichiometric L1 2 type NiAl3, L1 2 type Ni3Al, L1 0 type NiA; and B2 type NiAl, are calculated using a constructed n-body potential model combined with molecular dynamics. Furthermore, the types of point defects in the ordered NixAl1-x （x = 0.25, 0.5, 0.75） systems in the nonstoichiometric case are discussed, to validate the model. The present calculation shows that the point defects are the antisites. It is in good agreement with other investigations. Then the n-body potential calculations are performed to investigate the site preference of ternary elements Mo/Ta/W alloying additions in the NixAl1-x systems. The occupation site of the ternary elements are analyzed based on the occupational energy minimizing. And the results show obviously that the occupational sites of Mo/Ta/W are the Al site.