中断时效处理对AA2024铝合金力学性能和显微结构的影响

Effect of interrupted ageing on mechanical property and microstructure of AA2024 alloy

采用热电力(TEP)、扫描电镜(SEM)和透射电镜(TEM)等显微表征技术,结合硬度和韧性测试,研究中断时效工艺(IA)对S相为主要强化相的AA2024铝合金的力学性能和显微结构的影响。合金经180℃欠时效处理后,分别在室温和65℃进行低温时效处理即中断时效(T6I4),然后在180℃进行再时效处理(T6I6)。结果表明:相比T6工艺,T6I4工艺处理的合金可以获得较好的韧性,但硬度略有降低;而T6I6工艺会同时降低合金的韧性和硬度。低温中断时效处理时,欠时效过程形成的S相基本不发生变化,合金内部形成的原子团簇可能是T6I4状态韧性提高的原因。T6I6再时效过程中没有形成更多的S相,且原有的S相明显粗化,T6I6峰值时效状态下,合金力学性能变差;AA2024合金中断时效过程中没有析出能够形成S相的形核点。

The effect of interrupted ageing（IA） on the mechanical property and microstructure of AA2024 alloy,in which the S phase serves as the main strengthening phase,was investigated by the thermal electrical power（TEP）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM） and hardness and toughness tests.The interrupted ageing at room temperature or 65℃ was implemented on samples under-aged at 180℃ for T6I4 treatment,then re-ageing at 180℃ for T6I6 treatment.The results show that the T6I4 treatment can render better toughness and slightly lower the hardness of AA2024 alloy compared with T6 temper,presumably because of atomic clusters form during IA.Unfortunately,both hardness and toughness are worse after T6I6 treatments,under which,no precipitation of additional S phase but coarsening ones can be observed.It is thus reasonable to conclude that the low-temperature IA is not favorable to produce more S phase nucleus which can grow further during re-ageing.