Impacts of Rare Earth Element La on Properties and Microstructure of AlMgSi Alloys
Received date: 2022-06-16
Revised date: 2022-07-26
Online published: 2022-08-29
Supported by
National Natural Science Foundation of China(52001119);National Natural Science Foundation of China(51831004);National Natural Science Foundation of China(52171006)
The 6xxx series aluminum alloys Al-Mg-Si(-Cu) are widely used in the automotive industry owing to their high strength-to-weight ratio, good formability, and corrosion resistance. Micro-alloying is an effective technique for enhancing the properties and microstructure of Al alloys. The effects of varying La additions on the microstructure and properties of Al-0.75Mg-0.75Si (mass fraction, %) alloy have been investigated using hardness, electrical conductivity, and tensile tests, as well as SEM and TEM. As the La content increases, the following observations are made: (1) the ductility and electrical conductivity of the alloy gradually increase due to the increase in the fraction of the AlSiLa secondary phases induced by the La addition and the amount of Si solute atoms consumed by these phases; (2) the strength of the alloy first increases due to the increase in the secondary-phase strengthening contribution of the AlSiLa phases and the grain refinement contribution, and then decreases owing to the decrease in the solid-solution strengthening contribution; and (3) the types of precipitates formed during aging gradually change; besides the β″ phase, polycrystalline β″ precipitates are also precipitated in the peak-aged alloys with La addition, while β″/U2, β′/U2, and β′/U2/β″ composite precipitates are precipitated in the over-aging condition of the La-added alloys.
ZHENG Xiong , LAI Yuxiang , XIANG Xuemei , CHEN Jianghua . Impacts of Rare Earth Element La on Properties and Microstructure of AlMgSi Alloys[J]. Acta Metall Sin, 2024 , 60(1) : 107 -116 . DOI: 10.11900/0412.1961.2022.00298
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