纯钨高压扭转晶界演化和非平衡晶界形成机理  

Grain Boundary Evolution and Forming Mechanism of Non-Equilibrium Grain Boundary of Tungsten in High Pressure Torsion

作　　者：薛克敏[1] 周玉峰[1] 王雪[1] 李萍[1] Xue Kemin;Zhou Yufeng;Wang Xue;Li Ping(School of Materials Science and Engineering,Hefei University of Technology,Hefei 230000,China)

机构地区：[1]合肥工业大学材料科学与工程学院,安徽合肥230000

出　　处：《稀有金属材料与工程》2022年第7期2545-2551,共7页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51675154,51705118,51875158)。

摘　　要：本研究在550℃下对纯钨分别进行了1、2、5和10圈的高压扭转变形,并对变形前后的微观组织进行了EBSD和TEM表征。结果显示,纯钨经过大塑性变形后,晶粒得到细化,大角度晶界比例上升,同时晶内位错逐渐向晶界处移动并产生有序化排列。采用修正位错模型对变形前后的晶界能量进行了计算,计算结果表明纯钨在经过大塑性变形后,晶界上的能量升高并且能量主要来自于变形过程中在晶界处积累的额外位错。同时在变形后的试样中观察到了一种特殊的非平衡晶界,分析可知非平衡晶界的形成条件是材料晶粒尺寸在位错平均自由程以下,并且是在大塑性变形材料中形成的。其在TEM高分辨下的形貌特征表现为较宽的晶界厚度和晶面干涉形成的莫尔条纹。The experiments of high pressure torsion(HPT) subjected to tungsten were conducted under 1, 2, 5 and 10 turn at 550 ℃. The microstructures of sintered and HPT-processed tungsten were characterized by electron backscatter diffusion(EBSD) and transmission electronic microscopy(TEM). The results show that after the large plastic deformation of W, the grains of sintered tungsten are refined and the proportion of high angle grain boundary increases. Meanwhile, the dislocations move towards the grain boundary and rearrange orderly during HPT process. The grain boundary energy of sintered and HPT-processed tungsten were calculated by modified dislocation model. It is found that the grain boundary energy keep increasing after large plastic deformation and the energy mainly comes from the excess dislocation accumulated at the grain boundaries during the deformation process. Also, the non-equilibrium grain boundary is observed in the deformed sample. It is only formed in materials with grain size below the mean free path of dislocations and in materials with severe plastic deformation. In high resolution TEM, it shows the features of thick grain boundary thickness and Moire fringes caused by crystal plane interference.

关 键 词：纯钨 高压扭转 晶界演化 非平衡晶界 

分 类 号：TG301[金属学及工艺—金属压力加工]