预变形对LY12铝合金板热处理后晶粒度的影响

为了制定合理的铝合金板多道次成形工艺,需确定每道次的粗晶临界应变.通过将单向拉伸试件拉伸到不同预应变,然后热处理测定晶粒度的方法,分别研究了不同预变形对退火和淬火热处理后LY12铝合金板晶粒度的影响.结果表明,不同预变形对退火热处理后晶粒度无影响;对淬火热处理后晶粒度影响显著,而且存在一个临界应变,当预应变大于该临界应变时,晶粒突然长大.对于包铝层,该临界应变小于0.8%;对于基体,该临界应变在4%左右.对于LY12铝合金板多道次成形工艺设计,退火前道次极限变形量的制定不需考虑粗晶影响,淬火前道次变形量的制定需考虑粗晶临界应变.

Effect of predeformation on the grain size of LY12 aluminum alloy sheet after heat treatment

The critical strain of grain coarsening needs to be determined in order to define reasonable process parameters in multistage forming of aluminum alloy sheet. The effects of predeformation on the grain size of LY12 aluminum alloy sheet after anneal and quench heat treatment are investigated respectively by determination of the grain size of uniaxial tension specimens with different predeformation after heat treatment. It is shown that the effect of predeformation on the grain size after anneal heat treatment is negligible. However,the effect of predeformation on the grain size after quench heat treatment is remarkable and there exists one critical strain. If the prestrain is larger than it,the grain size will increases largely. It is less than 0. 8% for the cladding and about 4% for the core. The effect of strain coarsening needs not to be considered in defining the limit deformation in the stage before annealing and the critical strain of grain coarsening needs to be considered in defining the limit deformation in the stage before quenching when the multistage forming process of LY12 aluminum alloy sheet is designed.