Investigation of Reaction Mechanism, Structure and Mechanical Properties of the In-situ Composites Fabricated in Al-V2O5-NiO System

Abstract

In this research, fabrication of an in-situ composite via aluminothermic combustion synthesis in Al–V2O5 system has been investigated. For this purpose, the mixed powders of Al and V2O5 with molar ratio of 28 to 3 were ball milled and then compressed. Differential thermal analysis was used to evaluate the temperatures of phase transitions. Using the peak temperature of the reactions, the samples were subjected to heat treatment. It was shown that the reduction reaction of V2O5 by Al is a stepwise process and V2O4 and V2O3 as the main intermediate phases and γ-Al2O3 and Al23V4 as the transmission phases were formed before the formation of Al3V and α- Al2O3. Microstructural studies showed that after sintering at the temperatures up to 1000 oC, Al8V5 phase is formed at the interface between the two phases of Al3V and α-Al2O3. Hardness and compression test results also showed that the hardness and strength of the samples increase with increasing heating temperature due to the formation of greater volume fraction of intermetallic compounds and ceramic phases, however, the compressive strain decreased because of the formation of a greater amount of the brittle phase Al8V5.