Effect of Ti/C additions on the formation of Al3Ti of in situ TiC/Al composites

A novel technique for fabricating TiC particulate-reinforced commercial purity Al composites was introduced. The mechanism of formation of brittle Al3Ti up to 30 mum in size produced in the composites was studied and a method of eliminating them was put forward. The results show that: (1) the brittle Al3Ti phase is always present in the composites when the Ti:C molar ratio is 1:1. In this case, the tensile elongation of the composite was only 4%, much lower than the value of unreinforced aluminum (20%); and (2) the formation of the brittle Al3Ti phase can be eliminated entirely from the final product by using a proper Ti:C molar ratio of 1:1.3 in the Ti-C-Al preforms. In this case, the tensile elongation of this composite was 10%, higher than the value of the composite with a lot of Al3Ti (4%). Moreover, improvement in the tensile elongation of the composite was accompanied by an increase of the ultimate tensile strength. (C) 2001 Elsevier Science Ltd. All rights reserved.