The solution treatment of in-situ sub-micron TiB2/2024 Al composite

In this work, we studied the solution treatment of in-situ TiB2/2024 Al composite. In the composite, TiB2 particles have ranged from 30 to 500 nm, and the second phases (SPs) of theta and S were identified to coexist with TiB2. Furthermore, mechanical properties subjected to different solution temperatures (STs) for T4 state were investigated. It was found that the increase of ST can effectively improve mechanical properties of composite. The optimum ST for the composite was 505 degrees C, which was higher than ST (500 degrees C) typically used in 2024 Al alloy. To understand this phenomenon, a modified diffusion-controlled dissolution model for the composite has been proposed. In the classical model for the alloy, the dissolution process should depend on the initial radius of SP, solution time and ST. However, the TiB2 aggregates around SPs should act as particle shells to reduce the effective contact area between the alloy matrix and SPs. This covering effect has hindered the dissolution of SPs in the composite. In consideration of this effect, a modified diffusion-controlled dissolution model was proposed for the composite. The increase of the ST that was more approaching to the eutectic temperature was a required strategy to enhance the SP dissolution. (C)2016 Elsevier Ltd. All rights reserved.