The effect of magnesium on the strength and corrosion of AlSi12 alloy printed on an AA5056 substrate

Together, a scientific team from three laboratories - the laboratory of local metallurgy in additive technologies (LLMAT), surface hardening physics (LSHUP) and quality control of materials and structures (LKKMiK) - studied the structural-phase state, mechanical and corrosion properties of the composite alloy AA5056/AlSi12, created using wire electron beam additive manufacturing (EWAM).

The study showed that when printing AlSi12 alloy on AA5056, magnesium is present both in the transition region and in the printed AlSi12 layers. The highest Mg content was found precisely in the transition region, in which large Mg₂Si particles were formed after solidification.

The tensile strength of the printed AlSi12 alloy was higher than that of the original AlSi12 alloy, proving that mixing the printed AlSi12 alloy elements and the AA5056 substrate does not negatively affect the bond strength. The corrosion resistance of printed AlSi12 was also found to be high enough to protect underlying areas.

The most intense corrosion was observed on the surface of the transition zone, where large Mg₂Si eutectics dissolved. The corrosion potential values were found to be -732 mV for the transition zone, -545 mV for the printed AlSi12 layer and -695 mV for the AA5056 substrate.

The process of electrochemical corrosion in a sodium chloride environment was studied. Mg₂Si particles, which are anodic with respect to the aluminum matrix, dissolve, forming Mg(OH)₂ and SiH₄ compounds. The interaction of silane with water leads to the formation of the compound SiO₂·H₂O. Corrosion in the AA5056 substrate begins with the dissolution of the matrix, since the Fe-Mn particles are cathodic with respect to it. The printed AlSi12 alloy contains ?-Al+Si eutectic with small Mg₂Si particles, which form small pittings when dissolved.

Dissolution of Mg₂Si (a), formation of SiO₂ on Mg₂Si particles (b) and dissolution of the aluminum matrix (c)

The work was carried out within the framework of the state assignment of the Institute of Physical Problems and Problems of the Siberian Branch of the Russian Academy of Sciences (project FWRW-2022-0004). The research results were published in the journal Materials Characterization (IF: 4.7, Q1 in the Condensed matter physics category - according to SJR).

The results were published in the article: Veronika Utyaganova, Andrey Vorontsov, Denis Gurianov, Nikolai Shamarin, Andrey Chumaevskii, Konstantin Rubtsov, Nikolai Savchenko, Sergei Tarasov, Effect of Mg admixing on strength and corrosion of electron beam additive manufactured AlSi12 on the AA5056 substrate, Materials Characterization, 2023, 113172, ISSN 1044-5803,
https://doi.org/10.1016/j.matchar.2023.113172.