Pacific National University, Khabarovsk, Russia:

E. H. Ri, Head of the Department of Steel Casting and Technology of Metals
Hosen Ri, Professor at the Department of Steel Casting and Technology of Metals
M. V. Kolisova, Postgraduate Student at the Department of Steel Casting and Technology of Metals

National University of Science and Technology MISiS, Moscow, Russia:

V. B. Deev, Professor at the Department of Casting and Materials Working, e-mail: deev.vb@mail.ru.

With the help of optical and electron scanning microscopy and X-ray microanalysis, the authors of this paper looked at the formation of structural components in the АМ4.5Cd alloy and their properties when the alloy was doped with a growing amount of scandium (from 0.1 to 0.5% (wt)) with the interval of 0.1% (wt). The first stage of the research focused on identifying the structural components of the scandium alloy (2.0% (wt) Sc) that consists of 73.64% (at) Al and 26.34% (at) Sc (Al_73.64Sc_26.34 = Al_2.8Sc ≈ Al₃Sc) and the metal matrix comprised of Al + eutectic (Al + Al₃Sc), % (at): 99.67 Al and 0.33 Sc. The scandium aluminide particles are of compact quadrangular shape and are evenly distributed in the matrix. The authors analysed how scandium doping influenced the structure, segregation and properties of the АМ4.5Cd alloy. Microstructural analysis of scandium alloys in backscattered electrons in a scanning microscope and in an optical microscope showed that a bigger addition of scandium would contribute to the refinement of the structural components — i.e. solid α-solution and eutectic. The authors established and provided scientific evidence to substantiate how the composition of the solid α-solution and the eutectic of different compositions and origins, as well as their microhardness correlate with the amount of scandium added. The doped eutectic is crystallized when 0.1% (wt) Sc is added. When the scandium dope is raised to 0.5% (wt), the concentration of copper and scandium in the solid α-solution rises (to 1.5 and 0.74% (at), respectively, in comparison with the undoped solution — 1.0% (at) Cu). Correspondingly, the microhardness of the solid α-solution rises 1.85 times. The hardening effect becomes stronger due to fine-dispersed particles of the Al₂Cu and Al₃Sc phases that precipitate when the casting is cooling down. The microhardness of the eutectic is influenced by the distribution of elements in the eutectic components of different alloys of various origins: Al – Cu, Al – Cu – Sc, Al – Cu – MnFe and others. The scandium dope raised to 0.5% (wt) leads to the formation of eutectic components with increased concentrations of Cu and Sc. Thus, in the eutectic Al + Al₃Sc, the concentration of copper rises from 25% (at) for the undoped solution to 30% (at) Cu, and in the eutectic Al – Cu – Sc (Al + Al₃Sc + Al₂Cu) – to 32% (at) Cu and 5.5% (at) Sc following the addition of 0.5% (wt) Sc. The microhardness of the eutectic rises 3.0 times. The overall hardness HB rises ~1.4 times. Decreased solubility of copper and manganese is observed in other cadmium and iron containing eutectics.
This research was funded by the Ministry of Education and Science of the Russian Federation under the Governmental Assignment No. 11.3014.2017/4.6 “Understanding the possibility of producing REM containing addition alloys for metal alloy doping”. The research was conducted on the equipment owned by the Prikladnoe Materialovedenie centre of the Pacific National University with the funding provided by the Ministry of Education and Science of the Russian Federation under the Governmental Assignments No. 11.7208.2017/7.8 and 11.7213.2017/7.8.

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