材料期刊网

采用XRD、EBSD和TEM技术对单晶高纯Cu (99.999%)经等通道转角挤压(ECAP) A路径过程中的形变织构进行了研究,测试了ECAP后单晶Cu的力学性能和导电性能,并分析了变形过程中织构演变机理及其对力学性能和导电性能的影响。结果表明：原始单晶Cu经2道次变形后,晶内出现了微小的等轴状形变结构;4道次变形后,形成了(110)取向一致的形变带结构;8道次变形后,单晶组织开始破碎,晶粒取向又逐渐趋于(111)面,形成了{111}<110>和{111}<112>织构及较弱的{001}<100>再结晶织构。中、低应变下,形成稳定取向的{hkl}<110>织构,可有效降低晶界对电子的散射作用,使电导率略有增加,同时有利于大幅度提高材料的加工硬化率。单晶Cu变形初始阶段形成了大量小角度晶界,随着应变的增加,小角度晶界逐渐向大角度晶界转变。由于变形过程中位错积聚及晶界密度增加对位错运动起到阻碍作用,3道次变形后,抗拉强度从168 MPa增加至400 MPa,延伸率从63%减小至27.3%,在随后的变形中抗拉强度增加缓慢,延伸率略有回升。前8道次变形中硬度不断增加,8道次变形后出现了再结晶,导致随后的挤压过程中硬度不稳定。

The single crystal copper has got more and more attention in the important areas of the national economy due to its good conductivity and thermal conductivity and elongation. Whereas the lower strength limits its application and strengthening methods of single crystal copper are of great concern. The traditional strengthening methods, such as solid solution strengthening, fine grain strengthening and deformation strengthening, can seriously damage the conductivity of single crystal copper. As an effective method for severe plastic deformation (SPD), equal channel angular pressing (ECAP) can effectively improve the material strength and keep its excellent performance by controlling the deformation and strain. Deformation texture of the single crystal copper (99.999%) during ECAP by A route was investigated by XRD, EBSD and TEM, the mechanical properties and conductivity were tested, and the mechanism of texture evolution and influence factors of mechanical and electrical properties during deformation process were analyzed. The results show that equiaxed deformation structure with small sizes appeared in single crystal copper after two passes extruded. After four passes of deformation, deformation band structure with same (110) orientation was formed. And the grain orientation of the highly refined grains gradually tended to the (111) surface, the {111}<110>, {111}<112> textures and the little {001}<100> recrystallization texture formed. The scattering of electrons by grain boundaries (GBs) can effectively get reduced and conductivity increases slightly, at the same time, the work hardening rate of the material is significantly improved when {hkl}<110> texture with stable orientation forms under medium and low strains. A large number of low-angle grain boundaries (LAGBs) are formed in the initial deformation stage of single crystal copper. With the increase of strain, the LAGBs gradually change to the high-angle grain boundaries (HAGBs). Dislocation accumulation and GB density increase that dislocation movement is obstructed during deformation process. The tensile strength increases from 168 MPa to 400 MPa, the elongation decreases from 63% to 27.3% after three passes deformation. With the extrusion process, the tensile strength increases slowly, whereas the elongation increases slightly. When the extrusion pass is less than eight times, hardness increases continuously, and recrystallization occurs after eighth passes extrusion that hardness tends to be unstable.