AZ31B镁合金板材波-平与平-平轧制微观取向研究

Micro-orientation of AZ31B Magnesium Alloy Sheet Prepared by Longitudinal Wave Rolling and Flat Roll Rolling

为探究纵波轧制(longitudinal wave rolling,LR)对AZ31B镁合金微观取向的影响,对AZ31B镁合金板材400℃/20 min和450℃/20 min热处理后,利用振幅0.35 mm,周期4 mm的纵波波纹轧辊和平轧辊进行了波-平和平-平二道次轧制。借助EBSD分析了轧制后板材波谷、波腰及波峰处的晶粒度及取向。结果表明:板材热处理后,基面织构强度和平均晶粒尺寸均降低,其中450℃/20 min热处理后基面织构强度下降显著,但其平均晶粒尺寸增加;400℃/20 min+LR后板材的平均晶粒尺寸显著降低,波峰和波谷处的基面织构强度较热处理试样增强,波腰基面织构强度几乎不变,然而因波峰和波谷大量晶粒分别沿RD的相反方向发生了偏转,故整体宏观织构强度显著降低;二道次轧制后,400℃/20 min+纵波-平辊轧制(longitudinal wave rolling+flat rolling,LFR)后波峰和波谷处的基面织构强度较400℃/20 min+LR后对应位置显著降低,而波腰强度显著增强,同时各处平均晶粒尺寸进一步降低。400℃/20 min+平辊-平辊轧制(flat rolling+flat rolling,FFR)后相比400℃/20 min+LFR,其基面织构强度弱于波腰而强于波峰和波谷处。故400℃下LFR后板材与FFR后板材的整体基面织构强度接近。450℃/20 min+FFR后板材相比400℃/20 min+FFR后板材,其基面织构强度显著降低,{0001}<1120>类型织构占比更低,同时平均晶粒尺寸增大。

Longitudinal wave rolling+flat rolling(LFR)and flat rolling+flat rolling(FFR)was employed to roll AZ31B magnesium alloy sheet with the heat treatment of 400℃/20 min and 450℃/20 min,in order to investigate the influence of longitudinal wave rolling(LR)on the microscopic orientation of magnesium alloy.The amplitude of the corrugated roll was 0.35 mm and the period was 4 mm.The grain size and orientation at wave trough,wave waist and wave peak were analyzed by EBSD.The results show that both the basal texture strength and average grain size decrease after heat treatment.The basal texture strength decreases significantly after heat treatment of 450℃/20 min,while the average grain size increases.After 400℃/20 min+LFR,the average grain size of the plate decreases significantly,the basal texture strength at wave peaks and troughs increases compared with that of heat treated samples,and the basal texture strength of the wave lumbar is almost unchanged.However,due to the deflection of a large number of grains at wave peaks and troughs along the opposite direction of RD,the overall macro-texture strength decreases significantly.After the second pass,the surface basal texture strength at the peak and trough of 400℃/20 min+LFR is significantly lower than the counterpart after 400℃/20 min+LFR,while the wave waist strength is significantly enhanced,and the average grain size is further reduced.Compared with the case of 400℃/20 min+FFR,the texture strength of base plane is weaker than that of wave waist but stronger than that of wave peak and trough.Therefore,the overall base texture strength of LFR and FFR plates is close to each other at 400℃.The substrate texture strength of the plate after 450℃/20 min+FFR is significantly lower than that after 400℃/20 min+FFR,the texture proportion of{0001}<1120>type is lower,while the average grain size increases.