Study on Flake-Forming Behavior of Metal Powders by MA and Application of the Flaky Metal Powders to Al₂O₃ Composites

Abstract

New simultaneous toughening and strengthening method for Al₂O₃ composites has been reviewed. The flake-forming behavior of refractory metal powders such as Mo, Ta and Nb by MA process, and three-point flexural strength and fracture toughness of Al₂O₃ composites reinforced with flaky Mo particles have been investigated. The flake-forming behavior of Mo powders mixed with Al₂O₃ powders becomes prominent with increasing Mo particle size, while remaining almost independent of Mo volume percent. The fracture toughness increases with increasing Mo particle size which corresponds to an increase of the flake-forming tendency of these particles. Furthermore, the fracture toughness and flexural strength can be simultaneously improved by increasing the volume percent of flaky Mo particles. The microstructural observations indicate that the improvement in fracture toughness may be due to plastic deformation of Mo particles at a crack tip and crack-deflection or crack-bridging which are accelerated more by the flaky rather than the small. spherical shape.