镍铬合金中不全位错的透射电子显微镜观察

对镍铬合金(20％Cr,1％Al,2.5％Ti)中层错边界处及共格孪晶界面上的不全位错进行了观察和分析,结果是:1.用g·b_p=±2/3或±1/3作为不全位错是否显示衍衬是可行的,但不够严格。为此,应尽量选择{220}或{311}类型衍射成像,这时g·b_p或者等于零,或者等于整数,比较容易确定不全位错的柏氏矢量。2.共格孪晶界面上有不全位错,大多数是全位错分解的产物,成对出现。3.平行滑移面上的层错在运动中可以相互重迭。重迭层错中内禀层错与外禀层错之间的不全位错,在g·b_p=±2/3时无衍衬(在层错条纹的较强背景下是亮线),而在g·b_p=±1/3时显示衍衬(暗线)。关键词：

A TEM STUDY OF PARTIAL DISLOCATIONS IN A NICKEL-CHROMIUM ALLOY

The partial dislocations bordering a stacking fault and appearing on a coherent twin boundary in a Ni-Cr alloy (20% Cr, 1% Al, 2.5% Ti) were studied by TEM and the findings are as follows:1. The using of g·b_p=±2/3 or ±1/3 as the criterion of appearance or disappearance of partial dislocations is acceptable, though not rigorous. Therefore, it is preferrable to choose {220} or {311} reflections to form diffraction contrast image and use g·b_p = 0 to determine the Burgers vectors of the partial dislocations.2. Partial dislocation pairs appeared on coherent twin boundaries as a consequence of the dissociation of perfect dislocations.3. Stacking faults on parallel slip planes move and sometimes overlap each other. In overlapping faults the partial dislocations separating intrinsic and extrinsic faults showed no contrast when g·b_p = ± 2/3 and appeared as white lines on the dark background of stacking faults, while they appeared as dark lines when g·b_p= ± 1/3.