Effect of Heat Treatments on Microhardness and Roughness of Al-4Ti/1wt% MgO Composite

This work aims to study the effect of annealing, normalizing and tempering on optical microstructure, microhardness and roughness of Al-4Ti and its composite with 1 wt% MgO. The heat treatments were achieved at 500 ^oC. The results showed that normalizing and tempering led to decreasing the presence of main phase in Al-Ti alloy which is Al₃Ti through breaking up the phase in alloy, while the heat treatment led to enhance this phase in composite due to the incorporation between MgO and Al₂O₃ (which formed by convert aluminum to it) to form MgO.Al₂O₃. Therefore, in the optical examination of tempered Al-4Ti/MgO can be seen coarse Al₃Ti platelet particles in addition to MgO particles. Microhardness highly influenced by heat treatments, the base alloy had microhardness more than composite with MgO before heat treatment due to presence of porosity which can occur due to the difficulty in the wetting of the ceramic-based reinforcement elements by the matrix material Al. While heat treatments made the microhardness of composite is more than that for alloy due to the broken in hard intermetallic (Al₃Ti) in Al matrix. The data of roughness were higher for base alloy than composite due to decreasing and increasing the presence of Al₃Ti phase in alloy and composite respectively.

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