Grain Boundary Evolution and Forming Mechanism of Non-Equilibrium Grain Boundary of Tungsten in High Pressure Torsion [纯钨高压扭转晶界演化和非平衡晶界形成机理]

作者：Xue K.; Zhou Y.; Wang X.; Li P.^*

来源：Rare Metal Materials and Engineering, 2022, 51(7): 2545-2551.

• grain boundary evolution
• high pressure torsion
• non-equilibrium grain boundary
• pure tungsten

The experiments of high pressure torsion (HPT) subjected to tungsten were conducted under 1, 2, 5 and 10 turn at 550 °C. 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.

• 单位
  合肥工业大学