摘要
通过SEM原位拉伸实验观察室温下多晶Be的变形、裂纹萌生和扩展过程,利用电子背散射衍射(EBSD)标定断裂解理面,结合OM分析孪晶变形,研究多晶Be室温拉伸变形和断裂行为及其机理.结果表明,室温拉伸应力条件下,多晶Be的滑移和孪晶变形均难以发生.滑移带仅在少数取向有利的晶粒中出现,最终孪晶变形晶粒约占晶粒总数的5%.变形过程中存在(0001)基面和{1010}柱面之间的交滑移.多晶Be的微裂纹起源于晶界一侧,发生穿晶扩展后,在另一侧晶界终止,裂纹萌生符合Stroh位错塞积生裂纹理论.因晶界对裂纹强烈的阻碍作用,多晶Be的裂纹长大依靠不同微裂纹之间的汇合,汇合路径有解理台阶和撕裂2种.多晶Be断裂基本解理面为(0001)基面和{1010}柱面,两者均是多晶Be解理萌生和扩展的主要路径.未观察到因孪晶变形诱发的微裂纹.
Deformation and fracture behaviors as well as their mechanisms of polycrystalline beryllium at room temperature were systematically studied by in situ tensile test in SEM, characterizing fracture cleavage planes by electron backscattered diffraction （EBSD） technique, and twinning deformation analyzing by OM. The results show that slip and twinning deformation of polycrystalline beryllium are difficult to occur under tensile stress at room temperature. Slip bands happen only in some grains with a favorable orientation, and finally twin- ning deformation grain number accounts for only about 5% of the total grains. There exists the cross slip between （0001） basal plane and { 1010} prismatic plane in the deformation process. Microcracks usually initiate at one grain boundary, then propagate by a transgranular way and terminate at the other side of the grain boundary in polycrys-talline beryllium. Crack initiation of polycrystalline beryllium is in accordance with Stroh dislocation pile-up crack theory. The growth of microcracks have to depend on different microcracks merging by cleavage steps or tearing way due to a strong blocking effect of grain boundaries on the microcracks propagation. Basal cleavage planes of polycrystalline beryllium are determined to be （0001） and { 1010} planes. Both of them are the main paths of cleav- age crack initiation and propagation of polycrystalline beryllium. It is not observed that twinning deformation induces nucleation of microcracks.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2014年第9期1078-1086,共9页
Acta Metallurgica Sinica
基金
军品配套科研资助项目JPPT-125-GH-036~~
关键词
多晶Be
断裂机理
解理面
孪晶变形
polycrystalline Be, fracture mechanism, cleavage plane, twinning deformation
