预时效对T9I6工艺的2519A铝合金力学性能和组织演变的影响

Effects of pre-ageing on microstructure and mechanical properties of T9I6 heat-treated 2519A aluminum alloy

研究T9I6工艺中不同预时效时间对2519A铝合金的组织及力学性能的影响。通过硬度测试、室温拉伸试验检测合金的力学性能,通过透射电子显微镜(TEM)分析合金微观组织的演变,最后通过差示扫描量热法(DSC)分析合金的析出动力学。研究结果表明:预时效时间为80 min时,合金在峰时效状态的屈服强度和抗拉强度最高,分别为491.9 MPa和513.8 MPa,继续延长预时效时间会导致合金力学性能降低。合金的力学性能受预时效阶段生成的GP区影响,GP区可以阻碍由于位错运动造成的回复,并且在后续的时效过程中为θ′相提供形核点。预时效时间为40 min时,合金内没有足够数量的GP区阻碍位错运动。而预时效时间延长导致的合金力学性能下降,可能是由于过长的预时效时间消耗了大量基体内的过饱和溶质原子,导致断续时效过程中后续生成的GP区减少。同时,θ′相的粗化也是合金力学性能下降的原因。

The effects of pre-ageing on microstructure and mechanical properties of T9 I6 heat-treated 2519 A aluminum alloy were investigated by hardness tests, tensile tests, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC）. The results show that when the pre-ageing holding time is 80 min, both tensile strength and yield strength reach their maximum values, 491.9 MPa and 513.8 MPa respectively. However, further extending the pre-ageing holding time reduces the mechanical properties of 2519 A aluminium alloy. The mechanical properties of the alloy are associated with the formation of GP zones during pre-ageing. GP zones can greatly impede the recovery caused by dislocation movement and serve as precursors for θ′ precipitates during re-ageing. When the pre-ageing holding time is 40 min, an insufficient amount of GP zones is formed to act as effective obstacles for dislocation motion. The observed decrease in strength in samples subjected to extended pre-ageing holding time is caused by the depletion of the supersaturated solid solution atoms in the matrix and, consequently, decreases the nucleation of GP zones. Also, precipitate coarsening is another reason that causes the decrease of strength.