Abstract
The effect of La addition (0, 0.1, 0.2, 0.4, wt.%) on the microstructure, tensile properties and fracture behavior of Al-7Si alloy was investigated systematically. It is found that the La appears in the Al-7Si alloy in the form of Al4La and Al2Si2La phases. La addition can refine the secondary dendrite arm spacing (SDAS) and eutectic Si particles, which are decreased by 7.9% and 7%, respectively, with the optimal La content of 0.1wt.%. Because when 0.1wt.% La is added, a relatively higher nucleation undercooling of 37.47 °C is observed. Higher undercooling degree suggests that nucleation is accelerated and subsequent growth is restrained. After T6 heat treatment, compared with the without La, the ultimate tensile strength of the alloy with 0.1wt.% La is enhanced by 5.2% from 333 MPa to 350.2 MPa and the elongation increases by 73% from 7.37% to 12.75%, correspondingly. The fracture mode evolves from the ductile-brittle mixed fracture to ductile fracture mode. However, when La element content reaches a certain value of 0.4wt.%, serious segregation takes place during the solidification process. The formed brittle phases deteriorate the tensile properties of the alloy and the fracture mode of Al-7Si-0.2/0.4 La changes to mixed ductile-brittle fracture mode.
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Acknowledgements
This work was supported by the Fundamental Research Funds for the Central Universities (Grant number FRF-TP-19-083A1), the Guangxi Special Funding Programme for Innovation-Driven Development (Grant number GKAA17202008).
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Hai-tao Jiang Male, born in 1976, Ph.D, Professor. His research interests mainly focus on the processing and fabrication of metal materials. He has published above 200 papers in international and domestic journals so far.
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Wu, Xy., Luo, W., Zhang, Hr. et al. Effect of La addition on microstructure and mechanical properties of hypoeutectic Al-7Si aluminum alloy. China Foundry 18, 481–487 (2021). https://doi.org/10.1007/s41230-021-0137-4
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DOI: https://doi.org/10.1007/s41230-021-0137-4