Zr-Sn-Nb合金异步轧制过程中初始取向对微观组织演变的影响

Effect of Initial Orientation on Microstructure Evolution of Zr-Sn-Nb Alloy During Asynchronous Rolling

摘要:

异步轧制通过搓轧效应降低了轧制力，能够显著影响锆合金的塑性变形行为，是一种优化Zr-Sn-Nb合金织构特性的有效途径。本研究在异速比1.13下对Zr-Sn-Nb合金板材分别沿RD-TD（0°样品）和RD-ND（90°样品）方向进行异步轧制，结合电子背散射衍射技术和晶粒内部取向差轴（IGMA）分析，深入探究了初始取向、变形量对异步轧制过程中显微组织演变、滑移系激活规律及变形机制的影响。结果表明，随着变形量的增加，2种取向样品的晶粒显著细化，小角度晶界比例逐渐升高。轧制过程中0°样品始终保持双峰织构，而90°样品织构由<0001>∥TD转变为双峰织构。IGMA分析显示，轧制初期2种试样均以柱面<a>滑移主导滑移变形，随着变形量增加，柱面<a>滑移与基面<a>滑移发生竞争。0°样品整个变形过程中由柱面<a>滑移主导，其他变形方式并不显著；而90°样品的塑性变形由｛｝孪晶、柱面<a>滑移、基面<a>滑移和锥面<a>滑移共同主导。

Abstract:

Asynchronous rolling reduces rolling force through the cross-shear effect, significantly influencing the plastic deformation behavior of zirconium alloys, and serves as an effective approach to optimize texture characteristics in Zr-Sn-Nb alloys. In this study, Zr-Sn-Nb alloy sheets were subjected to asynchronous rolling at a speed ratio of 1.13 along the RD-TD (0° sample) and RD-ND (90° sample) directions. By combining electron backscatter diffraction and intra-grain misorientation axis (IGMA) analysis, the effects of initial orientation and deformation amount on microstructure evolution, slip system activation, and deformation mechanisms during asynchronous rolling were investigated. The results demonstrate that with the increase in deformation, both oriented samples exhibit significant grain refinement and a progressive rise in the fraction of low-angle grain boundaries. Throughout rolling, the 0° sample retains a bimodal texture, whereas the 90° sample undergoes a texture transition from <0001>∥TD to a bimodal texture. IGMA analysis reveals that prismatic <a> slip dominates the early deformation stage in both samples. As strain accumulates, competition arises between prismatic <a> slip and basal <a> slip. In the 0° sample, prismatic <a> slip remains the predominant deformation mode, with negligible contributions from other mechanisms. In contrast, plastic deformation in the 90° sample is cooperatively accommodated by {102} twinning, prismatic <a> slip, basal <a> slip, and pyramidal <a> slip.