Effect of processing temperature on the microstructure of Al-7Ti master alloy and on refinement of  α-Al dendrites in Al-7Si alloys 

¹R & D Centre, Dept. of Mech. Engg, Siddaganga Institute of Technology, Tumkur 572 103, Karnataka, India

²R & D Centre, Dept. of Mech. Engg., Basaveshwar Engineering College, Bagalkot 587 102, Karnataka, India

Adv. Mater. Lett., 2015, 6 (3), pp 252-259

DOI: 10.5185/amlett.2015.5646

Publication Date (Web): Feb 22, 2015

Copyright © IAAM-VBRI Press

E-mail: vsauradi@gmail.com

Abstract

The present work aims at evaluating the grain refining performance of Al-7Ti master alloys with different microstructures on Al-7Si alloys. Al-7Ti master alloys were prepared in an induction furnace by salt route involving the reactions between K₂TiF₆ and molten Al. Reaction temperatures chosen for producing Al-7Ti master alloys were 800^oC, 900^oC and 1000^oC while reaction time was kept constant at 60min. These indigenously prepared master alloys at different temperatures were characterized by chemical analysis; particles size analysis, XRD and SEM/EDX microanalysis. Results of particle size analysis suggest that mean size of Al₃Ti intermetallic particles in Al-7Ti master alloys were increased from 15.8µm to 22.4 µm as temperature is increased from 800^oC-1000^oC. SEM/EDX studies revealed fine blocky morphology, large blocky and flaky/petal morphologies of Al₃Ti intermetallic particles in Al-7Ti master alloys at 800^oC, 900^oC and 1000^oC respectively. Results of grain refinement studies suggest that Al-7Ti master alloy prepared at reaction temperature of 800^oC shows better grain refinement performance on Al-7Si alloy when compared to the Al-7Ti prepared at 900^oC and 1000^oC. In future, the influence of reaction time on microstructural and grain refining behaviour of Al-7Ti master alloys will be evaluated and the performance of these Al-7Ti master alloys will be compared with Al-B and Al-Ti-B master alloys.

Keywords

Master alloy, grain refinement, Al-7Si alloy, microstructure.