Influence of thermo-mechanical processing of Al-5Ti-1B master alloy on its grain refining efficiency

Abstract

The influence of extrusion and heat treatment after extrusion on the microstructural changes and the grain refining efficiency of Al-5Ti-1B; master alloy have been studied in detail. Extruded Al-5Ti-1B master alloy has resulted in significant refinement in TiAl3 Particle size and change in its morphology from plate like to blocky type. Mean particle size of TiAl3 has decreased with increase in the extrusion ratio. The grain refining performance of the master alloy has improved with increase in the extrusion ratio. These changes are attributed to the fracture of TiAl3 particles during extrusion, which results in an increase in the number of nucleating sites for Al. However, heat treatment of the extruded master alloy has reduced its grain refining performance. Heat treatment after extrusion at the highest extrusion ratio has resulted in the dissolution of TiAl3 and TiB2 particles in alpha-Al matrix, leading to poorer grain refining efficiency of the master alloy. (C) 2003 Elsevier B.V. All rights reserved.