块体纯铜的多尺寸晶粒混合结构及力学性能

Multiscale Grain Structure and Mechanical Properties of Bulk Copper

为了获得具有较好塑性的电沉积块体纯铜，主要研究500℃以上不同退火制度下的微观结构（晶粒大小、位错组态等）演变与力学性能的关系。研究结果表明：在500—560℃之间退火保温2h的过程中，试样有正常晶粒长大和异常晶粒长大现象。530℃，2h退火后，试样强度与500℃退火后的相比反常升高，但同时保持较好的塑性，与金属材料常规退火处理后性能变化趋势不一致，原因在于其内部形成均匀的多尺寸晶粒混合结构以及位错、孪晶等缺陷的变化。这种混合结构中的超细晶晶界可阻碍位错运动使材料保持一定的强度，同时嵌于超细晶晶粒基体中的微米晶可吸纳更多的位错使材料承受较大塑性形变。晶粒内部位错缺陷减少，促使晶粒可进一步承载由于拉伸变形产生的位错缺陷，提高塑性；同时孪晶数量增多，孪晶片层厚度增加。孪晶界也可阻碍位错运动而提高材料的强度，较厚的孪晶片层可以吸纳位错从而提高材料塑性。孪晶数量及片层厚度的变化有利于提高材料的综合性能。研究结果可为超细晶纯铜在电子行业较高温环境中的应用提供一定的参考价值。

To improve the ductility of bulk electrodepesited copper, the microstructural （ grain size, dislocation defects etc. ） evolu- tion and the mechanical properties of the bulk copper annealed at above 500 ℃ were mainly investigated. The results showed that there existed normal grain growth and abnormal grain growth in the samples annealed in the temperature range of 500 - 560 ℃. After annea- ling at 530 ℃ for 2 h, compared with the sample annealed at 500 ℃, the strength was enhanced abnormally, but at the same time the ductility remained. The abnormal variation of properties was proved to be related to the uniform multiscale grain structures introduced by annealing at 530℃ and the changes of dislocations and twins. The high strength derived from the copious boundaries of ultrafine grains which could hinder the movement of dislocations and the ductility originated from the micron grains embedded in the matrix of ul- trafine grains which could contain more dislocations. Meanwhile, the internal dislocation defects decreased, which promoted the grain to further bear the dislocation generated by tensile deformation and finally improved the plasticity. The density of twin and the thickness of twin lamellar relatively increased. Twin boundaries could also hinder dislocation motion to improve the strength of the material. The thicker twins could absorb dislocations to improve the plasticity. The variation of twins is helpful to improve the mechanical properties of the materials.