强变形Al-Cu合金的退火组织与性能

Annealed microstructure and properties of Al-Cu alloy processed by severe plastic deformation

研究时效Al-Cu合金强塑性变形后退火过程中的显微组织与性能的变化。制备分别只含θ″、θ′和θ相的时效Al-Cu合金,在室温多向压缩变形(MAC)后进行低温退火,测试合金的拉伸性能,借助X射线衍射仪和透射电镜分析显微结构的变化。结果表明,合金中含θ″相和含θ′相试样分别在MAC变形8道次和12道次时,析出相完全回溶于基体,形成过饱和固溶体。在退火过程中,基体发生回复,并伴随粒子再次析出,产生析出强化,再析出速度比同温度下的常规时效快。在120℃退火时,析出相完全回溶的含θ″相试样和含θ′相试样的强度分别在前60和30 min上升,而析出相未回溶的含θ相试样的强度则下降;在150℃退火时,析出相完全回溶的含θ″相试样和含θ′相试样强度与退火前强度基本持平,而析出相未回溶的含θ相试样强度明显下降;在200℃退火时,析出相回溶的试样和未回溶的试样强度都出现明显下降。说明强变形Al-Cu合金退火时强度取决于析出强化与回复软化的综合作用。在所有试样中,MAC变形8道次的含θ″相试样在120℃下退火60 min,表现出最好的综合性能。

Annealed microstructure and mechanical properties of aged Al-Cu alloy severely deformed by repetitive multi-axial compression（MAC） at room temperature were investigated by tensile test,X-ray diffractometer（XRD） and transmission electron microscopy（TEM）.The results show that,after 8 and 12 MAC passes,respectively,the specimens containing θ″ phase and the specimens containing θ′ phase are processed into supersaturated solid solution due to re-dissolution of precipitated phases induced by severe plastic deformation.During subsequent annealing,recovery and re-precipitation occur simultaneously;moreover,new precipitates reappear in a significantly accelerated rate.During annealing at 120 ℃,the strength of the specimen containing θ″ phase and the specimen containing θ′ phase increase,after 60 and 30 min respectively,while the strength of the specimens containing θ phase decreases.The specimens containing θ″ phase and the specimens containing θ′ phase exhibite little change in strength when annealed at 150 ℃,while the specimens containing θ phase have an obvious decrease in strength;when annealed at 200 ℃,all specimens′ strength decreases considerably.Strength of annealed Al-Cu alloy processed by MAC is attributed to the combined influence of re-precipitation strengthening and recovery softening.The specimens containing θ″ phase exhibite the best overall mechanical properties after 8 MAC passes and annealing at 120 ℃ for 60 min.