超塑预处理01420铝锂合金层状晶粒组织的形成机制

Formation mechanism of layered grain structure during superplastic pre-treatment in 01420 Al-Li alloy

采用形变热处理法制备01420铝锂合金细晶板材,研究时效第二相对位错分布和层状再结晶组织形成的影响。结果表明:时效第二相沿板材法向呈梯度分布,在表面层分布均匀且含量较大,而在中心层主要沿平行轧制方向分布且含量较小;第二组粒子的这种分布方式导致轧制过程中在其周围形成的高应变区域也呈梯度分布,这是导致层状再结晶组织形成的主要原因;板材表面层为细小等轴的再结晶晶粒,平均粒径约为10μm;板材中心层再结晶晶粒呈长条状,平均尺寸约为30μm×12μm;各层约占板材总厚度的1/3。

Fine grained 01420 Al-Li alloy sheet was produced by thermo-mechanical processing. The precipitation behavior of the second phase particles and their effects on the distribution of dislocations and gradient recrystallized grains were investigated. The results show that after aging, a gradient distribution of the large particles through the thickness occurs. The particles in the surface layer （SL） distribute homogeneously with larger content whereas the particles in the center layer （CL） mainly distribute parallel to the rolling direction with smaller content. The subsequent rolling results in a corresponding gradient distribution of high strained regions around these particles, which is the main reason for the formation of the gradient grain structure. The SL contains a fine, equiaxed grain structure with an average grain diameter of 10 μm whereas CL contains coarse elongated dimension with average grain size of 30 μm × 12 μm, each layer accounts for about 1/3 of the whole thickness.