Solid state sintering and consolidation of Al powders and Al matrix composites

Abstract

As an attempt to depart from conventional transient liquid phase sintering practice, solid state vacuum sintering was studied in loose powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized (CIGA) or high purity Al powder. The high purity Al powder was generated by a gas atomization reaction synthesis (GARS) technique that results in spherical powder with a far thinner surface oxide. After vacuum sintering at 525 °C for up to 100 h, SEM results showed that the GARS Al powder achieved significantly advanced sintering stages, compared to the CIGA Al powder. Tensile results from the forged samples also showed that although its ultimate tensile strength is lower, 95 vs. 147 MPa, the ductility of the GARS pure Al sample is higher than the CIGA Al sample. Forging also consolidated a model powder-based composite system composed of an Al matrix reinforced with quasi-crystalline Al–Cu–Fe powders, where the same powder synthesis methods were compared. Auger surface analysis detected evidence of increased matrix/reinforcement interfacial bonding in the composite sample made from GARS powder by alloy interdiffusion layer measurements, consistent with earlier tensile property measurements. The overall results indicated the significant potential of using Al powders produced with a thin, high purity surface oxide for simplifying current Al powder consolidation processing methods.