Effect of anisotropic mechanism of W-2%wt Y2O3 alloy on DBTT and fracture analysis under small punch testing

Abstract

The high brittle-to-ductile transition temperature (DBTT) of tungsten is a significant concern that hinders its use as a structural material. This study employs small punch testing over a broad temperature range to investigate the anisotropic mechanism of DBTT in as-hot rolled W-2%wt Y2O3 specimens. RD-TD specimen exhibits the highest EUS(0.75/J), highest ELS(0.08/J) and lowest TSP (∼336 °C) in three oriented materials. Multiple factors were conducted individually, revealing that the similar dislocation density, and fraction of LAGBs are not the primary determinant of the observed variations in DBTT performance. RD-TD specimen with strong {111}<112> γ-fiber texture exhibits the highest Fm that is nearly twice as high as that of RD-ND specimen and almost three times as high as that of TD-ND specimen. The relationship between the grain morphology, such as aspect ratio present on the DBTT as well as fracture mode of the material is apparent. RD-TD specimen boasts superior plastic properties, which displays an annular crack with the dome-like structure at the core and small incisions at the periphery. While, the plasticity of TD-ND and RD-ND specimens are deemed inadequate, as evidenced by the emergence of multiple lengthy and linear cracks in a particular orientation upon initial cracking. The utilization of numerous superimposed loads and the sandwich configuration of Y2O3 particles in tungsten matrix have been discovered to promote the occurrence of delamination in the thickness direction of the RD-TD specimens. The stratified structure, texture, screw dislocations, and grain aspect ratio have been identified as the pivotal factors influencing the anisotropy on DBTT and fracture analysis.