Zr-4合金压缩形变行为的研究∗

摘要

密排六方结构的Zr 呈现弹塑性各向异性， 轧制工艺会使材料内部产生晶间应力。 准确地评估Zr 合金内部的晶间应力分布并明确其微观形变机制， 对其服役能力和使用寿命的准确评判具有重要的科学意义和应用价值。 利用中子原位衍射技术结合弹塑性自洽(EPSC) 模拟分析了Zr-4 合金的压缩形变行为， 加载方式为沿轧板厚度方向压缩。 研究中辅以非原位的背散射电子衍射测试进行织构演化分析及透射电镜(TEM) 测试分析缺陷形态。 EPSC 模拟可以定量地给出不同形变量下的形变机制， 并且计算结果可由TEM 实验佐证。 研究表明： 当形变量较小(< 0：55%) 时， 柱面{1010}<1120> ( 型) 滑移起主导作用； 随着塑性形变量的增加， 锥面滑移的作用增强， 且锥面{1011}<11¯23> (型)滑移的作用大于柱面 {10¯10}<11¯20>(型)滑移， 少量的锥面{10¯11}<11¯20>(型)和{10¯12}<11¯20>(型)滑移也存在。%Zirconium (Zr) has a hexagonal close-packed crystal structure, which exhibits elastic and plastic anisotropy. Internal stresses can be easily generated in the rolling process and the subsequent plastic deformation process. It is critical to evaluate the internal stresses and the deformation mechanisms of Zr alloy materials. The deformation behaviors of Zr alloy influence directly its service life and safety. In this work, compression deformation behaviors of zircaloy-4 (Zr-4) alloy have been studied by the in situ neutron diffraction technique combined with the elastic-plastic self-consistent (EPSC) simulation. A compressive external load is applied along the thickness direction of the rolled plate, which is called through-thickness compression. Electron back-scattered diffraction is used to analyze the texture evolution during the plastic deformation. Transmission electron microscopy (TEM) is used to measure the distribution of the defects in the deformed sample. The EPSC simulation provides the deformation mechanism quantitatively by fitting the in situ neutron diffraction data, and the simulated results is confirmed by the TEM observations. Results show that when the true strain is small (less than 0.55%), prismatic {10¯10}⟨11¯20⟩ (⟨a⟩ type) slip dominates; however, as the plastic strain is increased, the percentage of pyramidal{10¯11}⟨11¯23⟩(⟨c+a⟩type) slip becomes larger than that of prismatic{10¯10}⟨11¯20⟩ (⟨a⟩ type) slip, and the pyramidal {10¯11}⟨11¯20⟩ (⟨a⟩ type) slip and pyramidal {10¯12}⟨11¯20⟩ (⟨a⟩ type) slip may exist.