Effect of La and Ce alloying on microstructure and the thermal deformation mechanism of commercial Al–Mg–Si alloy

Abstract

The isothermal compression of the commercial Al–Mg–Si alloys with and without La and Ce alloying were carried out at deformation temperature rages from 370 °C to 520 °C with strain rate from 0.01 s−1–10 s−1, the microstructure evolution and deformation behavior were also investigated. The results show that La and Ce alloying induces the formation of La and Ce-rich second phase. Moreover, rare earth element Ce tends to interact Fe/Si elements and La induces precipitation of Mg2Si phase, leading to higher volume fraction of α-AlFeSi, La and Ce-rich intermetallics and Mg2Si phases formed in modified alloy than the La and Ce-free alloy. Due to higher recrystallisation resistance of intermetallic and strengthening effect of Mg2Si phases, the modified alloy exhibits higher flow stress at low deformation temperature. The difference in mechanical behavior between La and Ce-free and La and Ce alloying alloy gradually decreases because of the weakening recrystallisation resistance ability of intermetallic and the absence strengthening effect of Mg2Si phases at high deformation temperature. The processing map as well as constitutive equation of the alloys are established and verified to be accurate based on the flow stress. It indicates that La and Ce alloying could contribute to microstructural modification and strength improvement without compromising formability of commercial Al–Mg–Si alloy.

Keywords

• Al–Mg–Si–La–Ce alloy
• Thermal deformation
• Processing map
• Flow instability
• Constitutive equation