In situ Al3Ti-Al2O3 intermetallic matrix composite: Synthesis, microstructure, and compressive behavior

A fully dense in situ Al3Ti-Al2O3 intermetallic matrix composite containing about 30 vol% Al2O3 particles was prepared by combining squeeze casting wi th combustion synthesis using the chemical reaction between TiO2 and Al. Th e microstructure of the in situ composite was examined using x-ray diffract ion, scanning electron microscopy, and transmission electron microscopy tec hniques. Compressive behavior of the composite was investigated in the temp erature range of 25-600 degrees C and compared with that of the as-cast Al3 Ti alloy. The in situ formed spherical alpha-Al2O3 particles with a size of 0.2-1 mu m were uniformly distributed in the Al3Ti matrix. The grain size of the Al3Ti matrix containing a small amount of Al2Ti precipitate was 2-10 mu m. The compressive strength of the in situ composite was about 6-9 time s that of the as-cast monolithic Al3Ti alloy and could be maintained at tem peratures up to 600 degrees C. This was mainly attributed to the fine grain size of Al3Ti matrix and the rule of mixture strengthening of Al2O3 partic les. The existence of Al2Ti phase and high dislocation density in the matri x also contributed positively to the composite strength.