單晶Cu等通道轉角擠壓A路徑形變特征及力學性能

單晶Cu等通道轉角擠壓A路徑形變特征及力學性能DEFORMATION CHARACTERISTICS AND MECHANICAL PROPERTIES OF SINGLE CRYSTAL COPPER DURING EQUAL CHANNEL ANGULAR PRESSING BY ROUTE A

采用XRD、EBSD和TEM技術對單晶高純Cu(99.999%)經等通道轉角擠壓(ECAP) A路徑過程中的形變織構進行了研究，測試了ECAP后單晶Cu的力學性能與導電性能，并分析了變形過程中織構演變機理及其對力學性能與導電性能的影響。結果表明：原始單晶Cu經2道次變形后，晶內出現了微小的等軸狀形變結構；4道次變形后，形成了(110)取向一致的形變帶結構；8道次變形后，單晶組織破碎，晶粒取向又逐漸趨于(111)面，形成了{111}<110>和{111}<112>織構及較弱的{001}<100>再結晶織構。中、低應變下，形成穩定取向的{hkl}<110>織構，可有效降低晶界對電子的散射作用，使導電率略有增加，同時有利于大幅度提高材料的加工硬化率。單晶Cu變形初始階段形成了大量小角度晶界，隨著應變的增加，小角度晶界逐漸向大角度晶界轉變。由于變形過程中位錯積聚及晶界密度增加對位錯運動起到阻礙作用，3道次變形后，抗拉強度從168MPa增加至400MPa，延伸率從63%減小至27.3%，在隨后的變形中抗拉強度增加緩慢，延伸率略有回升。前8道次變形中硬度不斷增加，8道次變形后出現了再結晶，導致隨后的擠壓過程中硬度不穩定。

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 large plastic deformation (SPD), 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 equal channel angular pressing(ECAP) by A route was investigated by XRD, EBSD and TEM methods, 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 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 boundaries(HAGBS). Dislocation accumulation and GB density increase that dislocation movement is obstructed during deformation process. The tensile strength increases from 168 to 400MPa, 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.

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