Development of TiB2 reinforced aluminum foundry alloy based in situ composites - Part II: Enhancing the practical aluminum foundry alloys using the improved Al-5 wt%TiB2 master composite upon dilution

This is Part II of the two part study. Part I we dedicated to optimization of the fabrication of in situ TiB2 particulate reinforced aluminum matrix composites. In this part, efforts were made to confirm the strengthening effects of the Al-5 wt% TiB2 composite, as a "master composite", on the practical foundry alloys, i.e. AlSi7Mg0.3, AlCu4.5Si1.1 and AlZn6Mg0.5. Experimental work and theoretical analysis are presented to interpret the improved yield strength of the diluted composites as influenced by their microstructures. The theoretically predicted and fitted values were in good agreement with the observed microstructural features and particle distribution, strongly supporting the mechanisms we proposed. The remelting and diluting approach can achieve superior improvement in UTS with respect to the conventional halide salt route, while compromising less ductility of the final composite. This characteristic is attractive from both technological and economic standpoints. Technologically, the present work can assist in providing strengthening strategies for different aluminum foundry alloy systems. (C) 2014 Elsevier B.V. All rights reserved.