Ni_3Al合金硼原子占位及晶界偏聚

BORON OCCUPATION IN Ni_3Al ALLOY AND ITS SEGREGATION IN GRAIN BOUNDARY

依据ＬＩ２型金属间化合物八面体，四面体间隙的特点，并利用硬球模型计算了上述各类间隙的空球半径大小，发现Ｎｉ３Ａｌ合金中６Ｎｉ八面体间隙空球半径比其他间隙大，使硼原子更易进入６Ｎｉ八面体间隙由于富Ｎｉ－Ｎｉ３Ａｌ合金晶界比富Ａｌ－Ｎｉ３Ａｌ合金有更多的６Ｎｉ八面体间隙，所以硼在富Ｎｉ－Ｎｉ３Ａｌ晶界偏聚较多另外富Ａｌ－Ｎｉ３Ａｌ合金晶界原子间作用力比富Ｎｉ－Ｎｉ３Ａｌ合金晶界原子间作用力大，这也阻碍了硼进入富Ａｌ－Ｎｉ３Ａｌ晶界。

According to the charateristic of tetrahedral and octahedral interstices in Ll2 intermetallic compound, the radii of those interstices have been calculated by the hard sphere model. It was found that in Ni3Al alloys, the 6Ni octahedral interstices in Ni-rich grain boundaries are large than that in Al-rich Ni3Al alloys. So a large amount of boron segregates in Ni-rich grain boundaries. Moreover,the interaction of atoms in Al-rich grain boundaries is stnonger than that in Ni-rich grain boundaries,which also prevents boron at oms from entering Al-rich grain boundaries.