中间退火及轧制工艺对Al-Mg-Li合金塑性开裂及晶粒细化的影响

Effects of intermediate annealing and rolling on plastic failure and grain refinement of Al-Mg-Li alloy

采用机械热处理法制备Al-Mg-Li合金细晶板材,研究预热温度、中间退火温度及转向轧制对板材塑性开裂及晶粒细化的影响。结果表明:板材在低温(≤300℃)轧制时往往开裂,将轧制温度提高到400℃,可获得无开裂的板材,但经再结晶退火后的晶粒组织粗大,约为16μm;降低中间退火温度虽然可以明显提高晶粒细化程度,但退火后采用单向轧制,当形变量较大时,板材会出现开裂问题;中间退火后采用转向轧制,不但大形变量下板材轧制不开裂,而且细化晶粒及减小板材厚度方向层状分布的程度,再结晶后2个表面层的晶粒细小等轴,平均晶粒粒径为9.26μm;中心层晶粒组织相对粗大略成扁平状,平均晶粒粒径为12.73μm,约占板材总厚度的1/5。

Fine grained Al-Mg-Li alloy sheets were produced by thermo-mechanical processing. The effects of preheating temperatures, intermediate annealing temperatures and cross-rolling on failure and grain refinement of an Al-Mg-Li alloy plate were investigated. The results show that low temperature rolling （≤300℃） usually leads to failure of the plate. Non-fractured sheets can be obtained by rolling at the enhancing temperature of 400℃, which results in a coarse grain structure with grain size of about 16 μm after recrystallization. Intermediate annealing at lower temperatures gives rise to finer grains, but if a unidirectional rolling is applied after annealing, cracks occur when the rolling reduction is too large. However, direction-changing rolling after annealing not only eliminates the cracks during deformation but also enhances grain refinement and decreases layer grain structure through the thickness. The surface layer contains fine equiaxed grains of about 9.26μm whereas central layer contains coarse elongated grains of about 12.73μm which accounts for about 1/5 of the whole thickness.