Effect of hot-working process on interface structure and ductile-to-brittle transition temperature of tungsten alloy reinforced by Al₂O₃ particles

The W-0.25 wt%Al₂O₃ alloy was fabricated by a powder metallurgy processing route, including hydrogen reduction, induction sintering and hot swaging. Al₂O₃ particles are absorbed on the surface of W particles with size ranging from 50 to 1000 nm. The microstructure of sintered alloy presents equiaxed grains with an average size of 8.6 μm and TEM result shows that a semi-coherent relationship exists in between W and Al₂O₃. After swaging, the swaged W-0.25 wt%Al₂O₃ alloy with fully dense was obtained. EBSD result indicates most of grains are obviously elongated and the average aspect ratio of W grains is 2.3:1. There is an obvious transition layer with a thickness of approximately 20 nm between W and Al₂O₃. The interface displays an amorphous feature because of uncoordinated deformation occurred in swaging process. 3-point bend tests show that the ductile-to-brittle transition temperature of sintered alloy is in the range of 350–400 °C. Moreover, the swaged alloy begins to exhibit obvious ductile behavior at 100–200 °C and the bending strength increases with increasing temperature, which reaches a maximum value of 1762 MPa at 400 °C.