Influence of titanium on structure formation, liquation processes and microhardness of structural components of Al – Ni – Ti alloys synthesized from the oxide phases by SHS metallurgy

The paper is devoted to revealing the regularities of the influence of titanium (0.91, 2.42, 3.19, 3.39, 4.32 and 8.81 wt.%) on structure formation, nature of element distribution and microhardness of structural components in Al – Ni – Ti alloys by aluminothermy during SHS metallurgy. As the initial composition of the charge were selected the following materials in fractional parts: Al:NiO 2 :CaF 2 :NaNO 3 :TiO 2 = 10:10:12:6: X , where X = 1.5, 4.5, 5.0, 7.0, 10.0. X The structural components in Al – Ni – Ti alloys have been identified by electron microscopy and X -ray spectral analysis XX of elements. In the alloys with 0.91–4.32 wt.% Ti the following phases crystallize: β′ -phase (solid solution of Ni in the nickel aluminide AlNi) Al 3 Ni 2 , Al 3 Ti, Al 3 Ni and α -solid solution of Ni and Ti in aluminum. In an alloy with 8.81 wt.% Ti the β′ -phase turns into a titanium-doped nickel aluminide Al(NiTi) (composition in at.%: 50.53 Al; 1.47 Ti; 48.0 Ni). The increase of titanium content in Al – Ni – Ti alloys increases the solubility of Ni in the β′ -phase and at titanium concentra- tion in the alloy 8.81 wt.% in the aluminide Al(NiTi) up to 48 at.% Ni is dissolved compared to the solubility of nickel (38 at.%) in the alloy with 0.91 wt.% Ti. Increasing the nickel content in the above phases contributes to their microhard- ness from 13 GPa to 14.8 GPa at 8.81 wt.% Ti. Increasing the titanium content in Al – Ni – Ti alloys to 4.32 wt.% increases the solubility of nickel in the nickel aluminide Al 3 Ni, with a higher concentration of titanium (8.81 wt.%) in the nickel aluminide with titanium Al(NiTi) dissolves up to 48.53 at.% Ni, while in the alloy with 0.91 wt.% Ti – only about 1.0 at.% Ni. At the same time, the Al and Ti content in titanium aluminide Al 3 Ti decreases and its microhardness increases. It was not possible to determine the microhardness of Al(NiTi) aluminide because of the formation of a porous structure. In nickel aluminide Al 3 Ni, an increase in titanium content leads to an increase in nickel concentration to 4.32 wt.% Ti followed by a slight increase to 8.81 wt.% Ti. Despite increasing the nickel content and decreasing the aluminum concentration, the microhardness of the nickel aluminide decreases. Apparently, this circumstance is caused by the formation of a porous structure in this phase.