Microstructure and viscosity of particles reinforced 7075 Al matrix composites

Abstract

In-situ TiB2 particle reinforced 7075 Al alloy was produced by molten salt method (LSM). The effects of TiB2 content on the microstructure, the melting behavior and the viscosity of 7075 Al alloy were investigated. The experimental results have shown that the microstructure became uniform rosette grains and the grain size decreased with increasing TiB2 particles. The morphology of grains became bigger with dendritic structure when the TiB2 particles content is more than 4.5%. The liquidus and solidus temperatures of the TiB2/7075 composites were firstly increased and then decreased with the increase of the content of TiB2 particles. The semisolid processing temperature window of 7075 Al alloy became narrow after adding TiB2 particles, and the liquid fraction of TiB2/7075 composites with increasing temperature was more sensitive than 7075 Al alloy. The apparent viscosity of the 4.5%TiB2/7075 composite was the lowest among 3.0, 4.5 and 9.0%TiB2/7075 aluminum matrix composites respectively. The apparent viscosity of the 9.0%TiB2/7075 was less than that of 7075 alloy but was greater than that of 4.5%TiB2/7075 composite under the same conditions. The viscosities of the composites decreased sharply with increasing shear rate, and the change with the shear rate were more sensitive than that of the 7075 alloy.