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A titanium‐aluminum composite coating was successfully fabricated on magnesium‐lithium alloy substrate by mechanical nano‐alloying treatment (SMNAT). The effects of aluminum content and mechanical nano‐alloying time on the microstructure and properties of titanium‐aluminum composite coatings were investigated. The experimental results showed that the ratio of titanium‐aluminum powder has a significant effect on the preparation of the coating. Low aluminum content and high aluminum content in the mixture powder resulted in the formation of the coatings with inhomogeneous thickness. The titanium‐aluminum ratio of 3 : 1 was considered to be optimal for fabricating the coating with homogeneous thickness under the selected milling parameters. The hardness of top surface layer on titanium‐ aluminum coatings decreased from 292.0 HV 0.01 to 121.4 HV 0.01 with the increase of aluminum content. Additionally, the prolongation of treatment time facilitated to increase the thickness and density of the coatings, resulting to enhance their hardness and corrosion resistance.

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In the present work, six specimens of hypo-eutectic Al-3Si-0.45Mg-0.45Cu-0.2Sc-0.2Zr cast alloys were made by a traditional casting process. The changes in microstructure and mechanical properties of the alloys at different Sr concentrations were studied using metallographic observation, tensile strength testing, and SEM analysis. The results show that, when the Sr content increased, the grain morphology underwent significant changes, from dendrites to isometric grains, and the Si phase in the eutectic region was greatly transformed and its grain sizes became smaller. However, over-modification, in excessive Sr content samples affected the mechanical performance overall. The best morphology with regards grain size and the silicon phase appeared in 0.06 % and 0.08 % Sr concentration specimens. The mechanical properties of the alloy were maximised and then decreased with increasing Sr concentration. The tensile test results indicated that the alloy with the best mechanical properties was that at 0.08 % Sr addition as evinced by its optimal morphological parameters.