Phase transformation of pure tungsten subjected to multi-directional compression

P Li and T Wu and JJ Shu and YF Zhou and X Wang and KM Xue, INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS, 86, 105086 (2020).

DOI: 10.1016/j.ijrmhm.2019.105086

Multi-directional compression (MDC) under the reduction of 30% with 1, 2 and 3 passes was subjected to tungsten at the temperature of 900 degrees C. The microstructure characteristics of the initial sintered and MDC- processed tungsten (W) specimens were comparatively investigated by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). The phase transformation from alpha-W to gamma-W was observed during the MDC deformation due to the crossed-shear deformation mode and high stored strain energy. An obvious crystallographic relationship of 110 alpha // 111 gamma was found between alpha-W and gamma-W. And a new crystalline slip path along 101 direction was presented. Molecular dynamics simulations were performed to investigate the phase transformation mechanism of pure W during MDC. A large number of defect clusters and shear bands were formed along <110> direction. Defect clusters huddled around the slip bands with the accumulation of strain, which caused dislocation tangling with the slip bands, resulting in stress concentration leading to phase transformation. The crystalline slip direction of alpha-W to gamma-W phase transformation was a complex of 100 and 001. The simulation results showed that the process of microstructural evolution under multiple passes of MDC was in good agreement with the experiment. This study is significant for the phase transformation path and mechanism of pure W during plastic forming.

Return to Publications page