强变形诱导析出相回归后的再时效行为

Re-ageing behavior of retrogressive precipitated phase caused by severe plastic deformation

利用透射电镜和硬度测量实验手段,研究了强变形诱导析出相回归后的合金在再时效过程中的组织、性能变化。发现:多相合金Al Zn Mg Cu经固溶、时效处理后,析出相粒子在强变形过程中破碎细化并可重新回归于基体内。强变形导致回归后的合金在再时效处理时可再次沉淀析出第二相粒子,但析出相的析出顺序与强变形后合金的晶粒尺有相关,当晶粒细化到某一临界尺寸以下时,析出顺序发生改变,非均匀形核的平衡相可抑制GP区、η′亚稳相等前期粒子的析出。

The microstructure and properties of an aged Al-Zn-Mg-Cu alloy associated with severe plastic deformation were studied by transmission electron microscopy and hardness measurement methods. The results show that the precipitates is fragmented and the retrogressive phenomenon of precipitated phase particles is caused by severe plastic deformation at room temperature condition. The sample which has retrogressive phenomenon precipitates the secondary phase during re-ageing treatment subsequently, and the reprecipitation sequence is due to the grain size caused by severe plastic deformation. There is a critical grain size below which the reprecipitation sequence changes, the heterogeneous precipitation of phase at grain boundaries would suppress precipitation of metastable phases such as GP zones and η′ phase.