Influence of Rare Earth Additions on the Microstructure and Mechanical Properties of Al7Si0.3Mg Alloys Processed by Semi-Solid Die Casting and Gravity Die Casting


Article Preview

Microstructures with fine globular grains and refined eutectic structures are important to enhance the mechanical properties of A356 alloys processed by semi-solid and gravity die casting. Rare earth (RE) additions have been shown to be capable of refining both the α-Al particles as well as modify the eutectic phase of alloys. In semi-solid die casting, Al7Si0.3Mg alloys with RE concentrations (0, 0.1 and 0.4 wt.%) were used to prepare semi-solid slurries using the SEED (Swirling Enthalpy Equilibrium Device) method, and subsequently semi-solid die cast. The same compositions of alloys were also applied to gravity die casting. The microstructure and mechanical properties of castings in two processes have been characterized. Compared to the grains produced in gravity die casting, globular grains with small size (260 μm) in the semi-solid die casting significantly enhance the UTS and elongation of alloys. Although the size of grains had no change with increasing RE concentrations in alloys. The Al-Si eutectics were changed to refined morphology with the 0.1 wt.% RE addition, which enhanced the ductility of alloys in two processes. When increasing the RE addition to 0.4 wt.%, the RE-rich phases precipitated at grain boundaries, which decreased the UTS and elongation of alloys.



Solid State Phenomena (Volume 285)

Edited by:

Qiang Zhu, Ahmed Rassili, Stephen P. Midson and Xiao Gang Hu




L. F. Li et al., "Influence of Rare Earth Additions on the Microstructure and Mechanical Properties of Al7Si0.3Mg Alloys Processed by Semi-Solid Die Casting and Gravity Die Casting", Solid State Phenomena, Vol. 285, pp. 69-74, 2019

Online since:

January 2019




* - Corresponding Author

[1] J. Langlais, A. Lemieux, The SEED technology for semi-solid processing of aluminum alloys: a metallurgical and process overview, Solid State Phenom. 116-117 (2006) 472-477.


[2] X.K. Liang, D.Q. Li, P. Côté, S. Midson, Q. Zhu, Comparison of Microstructure and Mechanical Properties of Semi-Solid Castings Produced Using Billets Made by EMS and SEED, Solid State Phenom. 217-218 (2015) 332-339.


[3] W.M. Jiang, Z.T. Fan, Y.C. Dai, C. Li, Effects of rare earth elements addition on microstructures, tensile properties and fractography of A357 alloy, Mater. Sci. Eng., A 597 (2014) 237-244.

[4] Z. Liu, Y.M. Hu, Effect of yttrium on the microstructure of a semi-solid A356 Al alloy, Rare Met. 27 (2008) 536-540.


[5] B. Nami, S.G. Shabestari, S.M. Miresmaeili, H. Razavi, Sh. Mirdamadi, The effect of rare earth elements on the kinetics of the isothermal coarsening of the globular solid phase in semisolid AZ91 alloy produced via SIMA process, J. Alloys Compd. 489 (2010) 570-575.


[6] X.M. Liu, Z. Liu, Y.M. Hu, Research on effect of La on microstructure in semi-solid A356 alloy, Adv. Mater. Res. 139-141 (2010) 693-697.


[7] M. Silva, A. Lemieux, X.G. Chen, Characterization of semi-solid slurry using a novel Rheo- Characterizer, apparatus, J. Mater. Process. Technol. 209 (2009) 5892-5901.


[8] B. Pourbahari, M. Emamy, Effects of La intermetallics on the structure and tensile properties of thin section gravity die-cast A357 Al alloy, Mater. Des. 94 (2016) 111-120.


[9] S.Z. Lu, A. Hellawell, The mechanism of silicon modification in aluminum silicon alloys: Impurity induced twinning, Metall. Mater. Trans. A. 18 (1987) 1721-1733.


[10] X.C. Song, H. Yan, X.J. Zhang, Microstructure and mechanical properties of Al-7Si-0.7Mg alloy formed with an addition of (Pr+Ce), J. Rare Earths, 35 (2017) 412-418.