Thermal cycling characteristics of in-situ Al-based composites prepared by reactive hot pressing

Aluminum-based composites reinforced with in situ Al3Ti plate and Al2O3 particle or with in situ TiB2 and Al2O3 particles were prepared by means of the reactive hot pressing method. These composites were fabricated from the TiO2–Al and TiO2–Al–B systems, respectively. Dilatometric testing was used to determine the influence of in situ reinforcement on the thermal expansion behavior of composites, and the effects of thermal cycling between 50 and 300 °C. Each cycle of thermal cycling process consisting of fast heating (15 °C/min) and relatively slow cooling rates (5 °C/min). The results showed that the in situ Al3Ti plate and Al2O3 particle formed from the TiO2-Al reaction leads to a decrease in the coefficient of thermal expansion (CTE) of Al. Moreover, in situ TiB2 and Al2O3 particles developed from the TiO2–Al–B system could further reduce the CTE of Al. Thermal cycling resulted in a net dimensional change of pure Al on the basis of the analysis of the thermal strains in the hysteresis loop. However, insitu composites exhibited a lower degree of damage compared to Al during thermal cycling.