Synthesis of Al -TiC in-situ composites: Effect of processing temperature and Ti:C ratio

Abstract

Al-TiC insitu composites are gaining increasing importance because of good wettability of TiC with Al melt and its favourable properties. However, incomplete reaction between the released Ti and C in Al melt leads to formation of undesirable phases like Al₃Ti which is detrimental to the properties. In this investigation, Al-TiC composites are processed at different temperatures from 700 °C to 1200 °C and with different Ti:C ratios to asses the effect of these two parameters on the formation of TiC particles. Microstructural features and X-ray diffraction results show that at temperatures below 1000 °C blocky type Al₃Ti forms. As the temperature is increased the blocky nature of Al₃Ti changes to needle like indicating release of Ti to a greater extent and as a result more and more TiC particles form. At 1200 °C there is no evidence of Al₃Ti formation after a reaction time of 30 minutes. Increasing the carbon content (Ti:C ratio) to two fold of the stoichimetric amount does not show any significant effect. Though a four fold increase in carbon content showed some promise, however, some amount of free carbon was found to remain.