The Evolution Of Microstructure And Texture Of Zr-Sn-Nb Sheet Druing Processing And Investigatation Of Deformation Mechanism Of Zr-Sn-Nb Sheet During Cold Rolling

In this paper, the characteristic of the evolution of microstructure and texture of Zr-Sn-Nb alloy sheets after different process were studied by EBSD and SE technology equipped in SEM and XRD. In addition, quantitative and qualitative study investigation of deformation mechanisms during cold rolling were studied applying in grain misorientation axis (IGMA) and crystal plasticity simulation respectively. Main conclusions drew from the research are as following:1) Grains in plate before hot rolling are equiaxial. Deformation bands along grain boundary are observed, and grains are elongated along RD after50%hot rolling. Elongated grains are split into several small grains after80%hot rolling. Deformation bands in80%hot rolled sheet are30°to RD. Remarkable growth of second phase particles is observed after annealing. Rolling after annealing will cause the decrease of the size of second phase particles. However, with the increase of the reduction, the size of SPP will increase slightly. The texture will change from random to typical tilt basal texture at the end of hot rolling. Texture nearly keeps stable during the subsequent cold rolling.2) Results of XRD and EBSD study on90°sheets and0°sheets show that initial orientation has significant effect on texture evolution of Zr-Sn-Nb sheet during cold rolling. There is a substantial change in the texture of90°sheet during cold rolling, from C(?)ND to double tilt basal texture. However, the texture of0°sheet keeps stable as double tilt basal texture during cold rolling.3) IGMA analysis illustrates that orientation plays a key role on the deformation mechanism.90°sheet is deformed by both slip including basal slip, prismatic slip and pyramidal slip and{102} tensile twinning. At small strain, the main deformation mechanisms are prismatic slip and{102} tensile twinning. However,0°sheets are only deformed by slip, and no twinning is observed in them. The relative activity of prismatic in0°sheet is less than that in90°sheet, however non-prismatic slip contributes more to the deformation of0°sheet than to that of90°sheet. At the same time, it was found that there is competition mechanism between pyramidal slip and twinning. The CRSS for the growth of{102} tensile is less than that for pyramidal slip, however, the CRSS for growth of{112} compressive twinning is higher than that for pyramidal slip. It is considered as the main reason that causes the difference of the deformation mechanism between0°and90°sheets.4) Relaxed constrain model is used to simulating texture evolution of the0°and90°sheets during cold rolling.The ratio of critical resolved shear stress of prismatic slip,{101} pyramidal<c+a> slip, basal slip and{102} tensile twinning is identified as1:5:9:2. The formation of the double tilt basal texture is ascribed to the combination of the operation of{102} tensile twining,{101} pyramidal<c+a> slip and basal slip, while the stability of texture during late stage of cold rolling is owing to the fact that the ratio of activation of basal slip and pyramidal slip keep constant. The<100>//RD texture is interpreted as a result of prismatic slip, and basal texture is due to the heterogeneity of deformation.