Effect of Si addition on mechanical alloying behavior and creep properties bf Al-10Ti-xSi alloys

Abstract

Al-10Ti-xSi alloys (x=0 similar to 6wt.%) have been mechanically alloyed under Ar atmosphere using an attritor and the alloying process has been investigated. From Al-10Ti composite powders, supersaturated Al(Ti) powders were obtained after mechanical alloying. In the ternary mixture, fine Si particles were observed to be distributed in the AI(TI) matrix due to both the negligible solid solubility of Si in the Al matrix and the weaker chemical interaction of Si with Al, as compared with Ti. The sealed compacts were hot extruded to full density at 450 degrees C with an extrusion ratio of 12:1. The microstructures and creep properties of the hot extruded alloys were examined. During consolidation, Si particles were dissolved in Al3Ti up to 4 wt.% Si to form the (AI(Si))(3)Ti phase, and the Ti7Al5Si12 phase was formed beyond the solubility limit of Si in Al3Ti. The transition from the Coble creep mechanism at low stresses and temperatures to dislocation one at high stresses and temperatures was observed. The stress and temperature of the transition from diffusional to dislocation creep became higher as Si concentration increased. This was due to an enhancement of Al3Ti particle strength with increasing Si content as a result of Si incorporation. Thus, the addition of Si enhances the creep resistance of the MA Al-10Ti alloy.