用正电子湮没技术研究Ni－20Al－30Fe合金中的缺陷组态

Defect configuration in Ni-20Al-30Fe alloys studied by the positron annihilation technique

测量了铸态、热轧和定向结晶三种不同工艺的Ｎｉ－２０Ａｌ－３０Ｆｅ的ｅ＋寿命谱：ｅ＋这三种试样的缺陷中的寿命十分相近．说明ｅ＋在该合金的空位、应错和晶界中的寿命相近．合金晶界缺陷处的自由电子密度和空位处的相当。在ＮｉＡｌ合金中加入Ｆｅ元素后．改善了合金的晶界结构．

Positron lifetime spectra have been measured for monodirectional crystal,as-cast polycrystal and hot-rolled polycrystal of Ni-20Al-30Fe alloys.τ2 values for these samples are similar,indicating that lifetime of the positron annihilated in grain boundary is similar to that in a vacancy or a dislocation,and density of free electrons in grain boundaries is nearly equal to that in vacancies.It is concluded that the structure of grain boundaries in NiAl alloy can be improved by alloying with Fe.