The structure, segregation and microhardness of the structural components of the Al – Ni – Zr alloys synthesized from nickel oxide NiO and brazilite concentrate by means of SHS metallurgy

Abstract

Intermetallide Al – Ni alloys can potentially be used to create materials with unique properties. Alloying with refractory transition metals plays an important role in building a strong combination of physico-mechanical and performance properties in alloys. Such alloys serve as an innovative material in various fields of technology. Aluminothermic reduction of oxides of various metals (including mineral concentrates such as scheelite, brazilite and other concentrates) and the use of SHS metallurgy help obtain complex alloyed aluminides of nickel. Thus, the production process becomes much simpler and the cost of producing new high-temperature materials decreases. The authors applied the technique of ladle aluminothermic reduction to nickel oxide NiO and brazilite concentrate to obtain zirconium alloys with the following concentrations of zirconium: 0.47, 1.05, 1.67 and 3.52 wt %. Optical and scanning electron microscopes were used to study the microstructure of the alloys. It was found that the addition of 0.47 wt % Zr leads to a dramatic refining of the structural components of nickel aluminides Al3Ni2 and Al3Ni. Nickel aluminide AlNi is quite rare to be found. A further increase in the addition of zirconium to 3.52 wt % resulted in slightly coarser structural components of the Al – Ni – Zr alloys. With the help of scanning electron microscopy and electron probe microanalysis, a multiphase structure was established and the structural components of the Al – Ni – Zr alloys were identified. It was established how the distribution of elements (segregation processes) and the microhardness of the structural components tend to change in the Al – Ni – Zr alloys.1. Apart from nickel aluminide AlNi, which solidifies primarily as small compact inclusions, Al3Ni2 and Al3Ni form in the initial Al – Ni alloy. The crystals of Al3Ni envelope the grains of Al3Ni2.2. The conducted research helped establish how elements tend to distribute in the structural components, and the structural components were identified – nickel aluminides AlNi, Al3Ni2 and Al3Ni with strengthening phases – alloyed with nickel aluminides with Zr, Si and others, as well as with aluminium zirconides.3. A relationship was established between the changing microhardness and the distribution of elements in the structural components of the Al – Ni – Zr alloys.This research was funded by the Ministry of Education and Science of the Russian Federation under the Governmental Assignment No. FEME-2020-0010 “Physico-chemical and process basis of metallothermic synthesis of metals in ion melts of alkaline metals and complex alloyed nickel aluminides by SHS metallurgy”. The research was carried out as part of research and development covered by the Scholarship of the President of the Russian Federation: SP-1904.2019.1 (2019–2021) using the equipment of the Shared Knowledge Centre “Applied Materials Science”, a part of the Pacific National University.