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. © 2002 Elsevier Science Ltd. All rights reserved.