淬火速率对汽车用新型高强韧铝合金晶间腐蚀的影响

Influence of quenching rate on intergranular corrosion of novel high strength and toughness automobile aluminum alloys

采用晶间腐蚀实验结合扫描和透射电镜分析,研究淬火速率对汽车用新型高强韧铝合金晶间腐蚀的影响。结果表明:淬火速率从960℃/s降低至1.8℃/s,晶界淬火析出相的长度及无沉淀析出带PFZ宽度分别从24.3 nm和23.7 nm增加至94.5 nm和97.8 nm,晶间腐蚀等级从3级增加至4级,最大腐蚀深度和平均腐蚀深度从71.6μm和60.3μm分别增加至174.2μm和157.9μm。随着淬火速率的减小,晶界析出相的粒径增加,晶界析出相的相间距增加,晶界PFZ宽度也相应增大,晶界析出相的Zn含量增加最快,Mg含量的增加次之,Cu含量的增加最慢,从而导致晶间腐蚀深度增加。

The influence of quenching rate on intergranular corrosion of novel high strength and toughness automobile aluminum alloys was investigated by intergranular corrosion experiments,scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that,when the quenching rate decreases from 960℃/s to 1.8℃/s,the size of the precipitates on the grain boundary and the width of precipitate free zone(PFZ)increase from 24.3 nm to 94.5 nm and 23.7 nm to 97.8 nm,respectively.In addition,the corrosion grade increases from 3 grade to 4 grade.The maximum corrosion depth and average corrosion depth increase from 71.6μm to 174.2μm and 60.3μm to157.9μm,respectively.The element contents of grain boundary precipitates are also altered during the quenching rate changing.That is to say,the increasing of Zn content is the fastest,followed by Mg content,and the increase of Cu content is the slowest,which results in the deepening of intergranular corrosion depth.