定向凝固镍基高温合金的塑性变形与γ′相中的位错结构

PLASTIC DEFORMATION AND DISLOCATION STRUCTURE IN γ'-PHASE OF A DIRECTIONALLY SOLIDIFIED Ni-BASE SUPERALLOY

本文利用透射电镜观察了定向凝固高温合金DS Rene80在拉伸及蠕变时的位错亚结构。试验结果表明:在低于760℃拉伸时,切割γ′粒子的是在{111}面上夹有APB的(1/2)〈110〉位错对。在不低于760℃拉伸时,切割γ′粒子的是在{111}面上夹有超点阵内禀层错(SISF)γ(1/3)〈112〉不全位错;这些不全位错在大应力的作用下于{111}面上将分解为一根(1/2)〈110〉螺位错和一根(1/6)〈112〉刃位错,并在其间夹有一个APB。在760℃,618MPa条件下蠕变时,切割γ′粒子的是在{111}面上夹有SISF的(1/3)〈112〉不全位错;这些不全位错此时不分解。与此同时,亦有(1/2)〈110〉位错对切割γ粒子。在980℃,190MPa条件下蠕变时,则无γ′粒子被切割的现象。在760℃,618MPa及980℃,190MPa条件下蠕变至第二阶段时,在γ/γ′界面上都形成了二维位错网络墙,墙上位错的攀移是合金形变的控制因素。第二阶段蠕变速率(ε)与立方γ′粒子的尺寸(α)和体积分数(V_f)的关系符合ε∝α/V_f^(2/3)

The dislocation substructure of directionally solidified DS Rene 80superalloy during tensile deformation and during creep deformation has been studied byTEM. In tensile deformation, γ' shearing occurs by slip of APB-coupled 1/2<110>dislocation pairs on {111} planes at temperature below 760℃, and by slip ofSISF separated 1/3<112> superpartials which have dissociated on {111} planes intoa 1/2<110> screw superpartial and a 1/6<112> edge superpartial with an APB inbetween at temperatures above or equal to 760℃. In creep deformation, γ' shearingoccurs again by slip of SISF-separated 1/3<112> superpartials which have not dis-sociated on {111} planes and by diffusive slip of APB-coupled 1/2<110> disloca-tion pairs at 760℃ under a stress of 618 MPa. However, no γ' shearing occurs at980℃ under a stress of 190 MPa. During secondary creep at 760℃, 618 MPa orat 980℃, 190 MP8, walls of dislocations have been formed at γ/γ' interfaces, strainis controlled by climb of 2-dimensional dislocation netwotks at γ/γ' interfaces.The dependence of secondary creep rate, ε, upon size, α, and volume fraction, V_f,of cubic γ' has been found to be ε ∝ α/V_f^(2/3).