Effects of trace C addition on the microstructure and refining efficiency of Al-Ti-B master alloy

The effects of a trace amount of C addition on the microstructure and refining performance of Al-Ti-B master alloy were studied and the Al-5Ti-0.8B-0.2C master alloy was prepared. Particles were extracted from the Al-5Ti-1B and Al-5Ti-0.8B-0.2C master alloys. In the Al-5Ti-1B master alloy, TiB2 particles exhibit hexagonal platelet and layered stacking morphologies, and agglomerate seriously in grain boundaries. After a trace amount of C is added, many paragenetic particles form in the Al-5Ti-0.8B-0.2C master alloy. They are composed of TiB2 particles and small TiC particles. The small TiC particles grow on the surface of TiB2 particles or are enchased in TiB2 particles. The existence of TiC particles weakens the TiB2 particle agglomerations obviously. Due to the microstructure improvement, the Al-5Ti-0.8B-0.2C master alloy shows much better refining performance than the Al-Ti-B master alloy. The average grain size of alpha-Al refined by 0.2 wt.% the prepared Al-5Ti-0.8B-0.2C master alloy is about 190 mu m. In addition, the refining efficiency of the Al-5Ti-0.8B-0.2C does not fade within 60 min. (C) 2010 Elsevier B.V. All rights reserved.