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

• TiB2 particles were identified to coexist with and the SPs.
• The TiB2 around SPs should act as particle shells to influence dissolution of SPs.
• A modified model was proposed for diffusion-controlled dissolution.

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 θ 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 °C, which was higher than ST (500 °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.

The TiB2 aggregates around second phases should act as particle shells to reduce the effective contact area between the alloy matrix and second phases.Figure optionsDownload as PowerPoint slide