AZ31B镁合金板材纵波与平辊轧制宏观织构演变

Macro Texture Evolution of AZ31B Magnesium Alloy Sheet During Longitudinal Wave and Flat Roll Rolling

为探究纵波轧制(LR)对AZ31B镁合金板材基面织构的影响,对AZ31B镁合金板材进行400℃/20min和450℃/20 min热处理以及振幅0.35 mm,周期4 mm的纵波波纹辊和平辊轧制。采用XRD对热处理及轧制后的板材进行宏观织构表征,运用极图及ODF对织构演变进行了分析,同时对金属在轧制变形区的变形行为进行了仿真分析。结果表明:板材热处理后,400℃下的{0002}极图中极密度最大值由11.21降到8.41,450℃下降到7.08,450℃下热处理后的织构强度弱于400℃;LR后板材的基面织构显著弱化,大量晶粒向RD、TD方向发生了偏转,其中向RD方向最多偏转30°,向TD方向最多偏转40°,400℃下的{0002}峰值织构强度降到4.33,450℃下降到5.62,400℃下LR的织构弱化效果比450℃更明显;二道次轧制后的板材,450℃下的基面织构强度要弱于400℃。分析表明:LR使得晶粒的c轴取向由ND向TD、RD方向发生了偏转,这是由于LR过程中存在类似于异步轧制过程中的“搓轧区”,其中产生的剪切力使晶粒沿RD方向发生偏转,弯曲和挤压复合变形下金属流动和剪切促进晶粒TD取向。

To investigate the effect of longitudinal wave rolling(LR) on the macro texture of AZ31B magnesium alloy sheet,the AZ31B magnesium alloy sheet was heat treated at 400 ℃/20 min and 450 ℃/20 min,and was longitudinal-wave rolled and flat-rolled with amplitude of 0.35 mm and period of 4 mm.XRD was used to characterize the macro texture of the heat-treated and rolled sheet,and the texture evolution was analyzed by polar diagram and ODF.Meanwhile,the deformation behavior of the metal in the rolling deformation zone was simulated.The results show that the peak texture intensity of {0002} at 400 ℃ is decreased from 11.21 to 8.41,and to 7.08 at 450 ℃.The texture intensity at 450 ℃ is weaker than that at 400 ℃.After LR,the substrate texture of the sheet is weakened significantly,and a large number of grains are deflected towards RD and TD with a maximum deflection of 30° towards RD and 40° towards TD.The peak texture intensity of {0002} is decreased to 4.33 at 400 ℃ and to 5.62 at 450 ℃.The texture weakening effect is more obvious at 400 ℃ than at 450 ℃.After two passes of rolling,the texture intensity of the substrate at 450 ℃ is weaker than that at 400 ℃.The analysis shows that LR makes the c-axis orientation of grains deflect from ND to TD and RD.The reason is that there is a “cross-shear zone” in the LR process similar to that in the asynchronous rolling process,in which the shear force promotes grains along RD.The metal flow and shear force promote the grain along TD under bending and extrusion combined deformation.