中间退火对Al-Mg-Si系铝合金汽车板组织和性能的影响

对Al-Mg-Si系铝合金汽车板进行了不同的中间退火处理(无中间退火、300 ℃×2 h、420 ℃×2 h),并利用光学显微镜、XRD、TEM、拓扑仪、拉伸试验机对板材进行了检测分析。结果表明,中间退火处理对T4P态板材的微观组织、织构、罗平纹和力学性能影响显著,提高中间退火温度有利于获得等轴晶粒、增大应变硬化指数(n值)、降低板材各向异性(Δr值),但塑性应变比(r值)也会有所降低。此外,经过300 ℃×2 h中间退火处理的板材在10%预拉伸后表现出最好的表面质量,无中间退火和420 ℃×2 h中间退火处理的板材在预拉伸后罗平纹缺陷严重。这主要归因于中间退火引发的板材微观组织和织构的差异。300 ℃×2 h的中间退火处理可以使Al-Mg-Si系铝合金板材在不降低力学性能的前提下显著改善罗平纹,表现出最佳的综合性能。

Effect of intermediate annealing on microstructure and properties of Al-Mg-Si series aluminum alloy automobile sheet

Effect of different intermediate annealing (IA) treatment, i.e. without IA, IA at 300 ℃ for 2 h and at 420 ℃ for 2 h, on the Al-Mg-Si series alloy sheet was investigated by means of optical microscopy observation, XRD analysis, TEM analysis, Topology instrument inspection and tensile test. The results indicate that IA treatment has obvious effect on the microstructure, texture, roping line and mechanical properties of the T4P treated sheets. Increasing the IA temperature is beneficial for obtaining equiaxed grains, increasing strain hardening exponent (n value) and reducing anisotropy (Δr value). But the average Lankford coefficient (r value) decreases. Furthermore, the sheet which IA at 300 ℃ for 2 h has the best surface quality after 10% prestretching, but the sheet without IA or IA at 420 ℃ for 2 h have a horrible roping line after pre-stretching. These differences can be attributed to the microstructure and texture transformation during the IA treatment. It can be concluded that the IA treatment of 300 ℃×2 h is better for the comprehensive performance of the Al-Mg-Si series alloy sheet.