本文利用显微硬度测试、拉伸试验、差示扫描量热法(DSC)和透射电子显微镜观察,研究了预时效对汽车车身板用6016铝合金烤漆前后微观组织和力学性能的影响.结果表明:经预时效处理的铝合金在室温放置1个月后硬度可保持在65 HV以下,延伸率可保持在25％以上,再经短时间烤漆处理后其硬度和屈服强度分别可提高至100 HV和220 MPa以上.与单级预时效处理后的合金相比,多级预时效处理后的铝合金烤漆前的力学性能更为稳定,烤漆后的硬度和强度更高.6016铝合金快速的烤漆强化效应与预时效处理后合金中形成的细小析出相在烤漆过程中快速长大有关.合金经预时效处理后铝基体内会形成非常细密且与基体完全共格的析出相,其长度约为2～3 nm,而经过烤漆处理后析出相沿〈001〉Al显著增长,长度大于10 nm.高分辨透射电镜分析显示烤漆后样品中形成的是具有单斜结构的针状GP区和β"前驱相.%The effects of pre-aging treatment on the microstructures and mechanical properties before and after paint bake cycle for a 6016 aluminium alloy were investigated by micro-hardness measurement, tensile test, differential scanning calorimetry ( DSC) , and transmission electron microscopy (TEM) . The experimental results show that the hardness and elongation rate of the alloy treated by pre-aging after 1 month's duration at room temperature could remain below 65HV and above 25% , respectively. Then, after paint bake cycle for a short time, the hardness and yield strength increased to over 100HV and 220MPa, respectively. Compared with samples through one-step pre-aging, the stability of the mechanical properties of samples treated by two-step pre-aging were higher, and the hardness and strength after paint bake were even higher. The quick bake hardening response in 6016 alloy was associated with the marked growth of the fine precipitates formed in the pre-aged samples during paint bake cycle. The fine, dense, and coherent particles, whose lengths were about 2 ~3 nm, precipitated in the pre-aged alloys. These particles grew remarkably in the paint bake cycle and became needle-like precipitates with a length above 10 nm. High-resolution TEM observations revealed that the precipitates were monoclinic GP zones and pre-β".
展开▼
