喷射成形7075铝合金欠时效回归再时效热处理

Retrogression and Reaging Treatment of Underaged Spray Forming 7075 luminum Alloy

采用透射电镜、拉伸测试等方法,研究欠时效回归再时效处理对喷射成形7075铝合金显微组织和力学性能的影响,并与单级峰值时效和常规回归再时效处理相比较。结果表明,采用120℃×12h欠时效预处理比120℃×24h峰值时效预处理更有利于在回归处理后合金晶内析出相的回溶,回归处理过程可使合金晶界析出相充分断开,再时效后晶内的析出相细小弥散,合金抗拉强度和屈服强度分别为776和723MPa,均高于T6峰值时效和常规回归再时效水平。

Effects of retrogression and reaging （RRA） treatment on microstructure and mechanical properties of underaged spray forming 7075 aluminum alloy were investigated by transmission electron micro- scope （TEM） and tensile testing, and compared with those of alloys under peak aging and conventional RRA treatment. The results show that underaging at 120 ℃ for 12 h as preaging treatment is more beneficial for the re-dissolution of precipitates in matrix than peak aging （T6, 120 ℃ × 24 h） in retrogression treatment. By retrogression treatment, the precipitates on the grain boundary are disconnected completely. After reaging treatment, fine and dispersed precipitates can be observed in the grain. And the tensile strength and yield strength of the alloy reach 776 MPa and 723 MPa, respectively, which are higher than those in T6 or conventional RRA treatment.