固溶前退火处理对2050铝锂合金冷轧薄板力学性能与组织的影响

Mechanical Property and Structure Variation of 2050 Al-Li Alloy Sheet Caused by Annealing Prior to Solution Treatment

采用拉伸性能测试、电子背散射衍射分析(EBSD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM),研究了固溶前退火处理(300℃/4 h,400℃/2 h)对2050铝锂合金冷轧薄板T8时效后力学性能、晶粒组织和析出相的影响。研究结果表明:固溶前退火处理导致2050铝锂合金冷轧薄板固溶态不完全再结晶数量增多,晶粒长厚比增大,小角度晶界比例增加,同时使合金Goss织构密度增大。T8时效后主要强化相为T1相和θ′相。固溶前退火处理可导致后续T8时效时T1相在不同{111}Al面上析出差异,其中部分{111}Al面上T1相析出减少,而预拉伸变形时承受高分切应力{111}Al面上T1相析出增加,从而影响合金的力学性能。固溶前300℃/4 h退火处理可使T8时效后合金屈服强度和抗拉强度提高,伸长率基本保持不变。

The mechanical properties,grain structures and precipitates of 2050 Al-Li alloy cold-rolled sheet in T8 temper with different annealing prior to solution treatment were investigated by tensile tests,electron backscattering diffraction analysis(EBSD),scanning lectron microscope(SEM)and transmission electron microscope(TEM).The results show that the number of incomplete recrystallization,the aspect ratio of the grains and the number of the low angle grain boundaries and the fraction of Goss texture increase in 2050 Al-Li alloy cold-rolled sheet with annealing prior to solution treatment.The main strengthening precipitates are T1 andθ′phase.The annealing prior to solution treatment leads to the precipitation differences of T1 phase on different{111}Al surfaces during T8 aging process.T1 phase number on some{111}Al surfaces decreases,while it increases on some{111}Al surfaces with high shear stress during pre-tensile deformation.This therefore changes the mechanical properties of the alloy.The annealing at 300℃for 4 h prior to solution treatment enhances the yield strength and the tensile strength of the alloy cold-rolled sheet with T8 ageing,but the elongation is kept unchanged.