Features of formation of the Al–Ni–Zr system alloy structure obtained by reducing oxide compounds by aluminothermy using SHS metallurgy

Abstract

This work is focused on establishing the regularity of the effect of zirconium (2.21; 3.29; 3.69 and 6.92 wt.% Zr) on structure formation, the nature of distribution of elements and the microhardness of structural components in the Al–Ni–Zr system alloys obtained by aluminothermy using the SHS metallurgy. Regularities of the formation of structural components and their microhardness depending on the content of zirconium in Al–Ni alloys (50 wt.%) have been identified and scientifically substantiated. Structural components were identified by the methods of electromicroscopic studies and X-ray microanalysis of elements. The structure of the initial alloy consists of Al3Ni2 (β′-phase) and Al3Ni nickel aluminides. Zirconium doping of the alloy in the amount of 2.21 wt.% leads to crystallization of zirconium nickel aluminide Al2(Ni,Zr). With further increase in the content of zirconium (more than 2.21 wt.% Zr), complex alloyed intermetallic compounds crystallize – Zr, W, Si aluminides and Ni zirconides. A regularity was established in the decrease of the solubility of nickel in nickel aluminides Al3Ni2 and Al3Ni and their microhardness as the zirconium content increases in the Al–Ni–Zr alloys from 2.21 to 6.92 wt.%. In nickel aluminide with zirconium Al2(Ni,Zr), this contributes to a decrease in the solubility of Ni, Al and increase in the concentration of Si and Zr. Zirconium doping of the Al–Ni alloy in the amount over 2.21 wt.% contributes to an increase in hardness (HRA), despite a decrease in the microhardness of the metal base (Al3Ni2, Al3Ni and Al2(Ni,Zr)). The main reason for increasing the hardness of the Al–Ni–Zr alloys is the crystallization of complex-alloyed intermetallides – Zr, W, Si aluminides and nickel zirconide, which probably have an increased microhardness. Thus, zirconium doping of the Al–Ni alloy makes it possible to obtain a plastic metal base from nickel aluminides Al3Ni2, Al3Ni and Al2(Ni,Zr) and complex-alloyed intermetallides with high hardness.