Structure, segregation and properties of high-alloy Al – Ti – V – Ni alloys

Abstract

Using optical and electron scanning microscopy, as well as electron probe microanalysis and X-ray diffraction analysis, the authors looked at the structure, segregation and properties (hardness HRA, microhardness HV) of high-alloy Al – Ti – V – Ni alloys. It was established how the structure tends to change and how elements of the structural components of the studied alloys (1–5) tend to distribute as a function of V and Ni concentration. Using electron probe microanalysis, the structural conponents of the studied alloys were identified depending on V and Ni concentration. 1. The initial alloy 1 sees vanadium aluminide Al3(V, Ti) solidify from Al – Ti – V – Ni (wt. %: 24.6 V, 0 Ni), as well as alloyed vanadium carbide. The former solidifies as grey-coloured grains with a minimum size of 25 μm and serves as the base phase, whereas tha latter comes in a spiky shape (<25 μm). A blackish-coloured mixture of Al + Al3Ti + Al21V2 solidifies last. 2. Alloy 2 sees nickel aluminide Al3Ni solidify from Al – Ti – V – Ni (17 wt. % V, 7.2 wt. % Ni) as fine-grained light-coloured inclusions against a background of vanadium aluminate Al2(V, Ti), which is the key structural component of the alloy. Together with the above phases, alloyed titanium carbide (Al, Ti, V)3C forms in the alloy as compact grey-coloured grains. A phase mixture of Al + + Al3Ni + Al3Ti + Al21V2 solidifies last. 3. The following phases solidify in alloys 3–5 from Al – Ti – V – Ni (0–10.7 wt. % V; 13.5–23.8 wt. % Ni): β'-phase – a solid solution of Ni in nickel aluminide AlNi, which comes as fine-grained white-coloured inclusions against a background of nickel aluminide Al3Ni, which is the base phase. The next phase includes compact dark-grey grains of titanium carbide Ti2C. Alloys 4–5 see a new phase form – a complex alloyed titanium aluminide Al3(Ti, V, Ni), which consists of dark-grey oblong-shaped crystals. A phase mixture of Al + Al3Ni + Al3Ti + Al21V2 solidifies last. Even though the stoichiometry of the identified phases fails to match the results of electron probe microanalysis, the results of X-ray diffraction analysis confirms the presence of the key structural components in the studied alloys.This research was carried out using the equipment of the Applied Materials Science Centre at the Pacific National University. It was funded by the Ministry of Education and Science of the Russian Federation under Gove rnmental Assignment No. FEME-2020-0010.