Adjusting the Si Phase and Forming Nanoprecipitation to Improve the Mechanical Properties of Al–Si–Cu–Mg Alloy by Heat Treatment

Abstract

To adjust the morphology of the Si phase and improve the mechanical properties of Al–Si–Cu–Mg alloy formed by semisolid squeeze casting, the effects of solution time on microstructure evolution and mechanical properties are systematically studied. Results show that spheroidization occurs in the Si phase, and the content of Cu in the matrix increases simultaneously after solution treatment at 525 °C for 1 h. As solution time increases to 8 h, the content of Cu in the matrix increases from 1.15% to 1.41% and the dislocation density decreases. After an aging treatment at 180 °C for 12 h, the β′, θ′, and Q′ phases precipitate. After heat treatment, the alloy strength value shows a “double peak” phenomenon. After a 1 h solution treatment, the tensile strength of the alloy reaches the first peak, which is mainly ascribed to the large dislocation density induced by the semisolid squeeze casting process. When the solution time is 8 h, the tensile strength of the alloy is 323 MPa and the tensile strength reaches the second peak, which is ascribed to the rounding of the Si phase and the strengthening effects of fine precipitates.

Effect of Heat Treatment Process and Optimization of Its Parameters on Mechanical Properties and Microstructure of the AlSi11(Fe) Alloy

“…Temperature of the solution treatment should be within range of 510–540 °C, while the artificial ageing temperature should be below 200 °C. Increasing the solution treatment temperature caused grain growth and the insoluble phases aggregated and coarsened, resulting in an enhancement of tensile strength [ 61 ], while low solution treatment temperature enables obtaining a large amount of homogeneously distributed phases, dispersing and hardening the alloy.…”

Effect of Heat Treatment on the Microstructure and Mechanical Properties of Al–9Si–0.4Mg–0.1Cu Alloy

“…[ 1–4 ] With the development of science and technology, higher requirements are put forward for the performances of Al–Si alloys to effectively alleviate energy consumption and environmental protection prospects. [ 5–7 ] Generally, alloying is the most frequently used method to optimize the composition of Al–Si alloys. For hypoeutectic Al–Si alloys, increasing the content of Si properly can not only improve the strength, but also promote the uniform precipitation of strengthening phases.…”