Kazuo Kasahara1, Kenki Hashimoto1, Haruo Doi1 and Tokuzou Tsujimoto1
1National Research Institute for Metals, Tokyo
The composition, crystal structure and hardness of TiAl(γ) phase contained in Ti-48--54 at%Al-0--12 at%Zr alloys annealed for 1 week at 1273 K have been studied. Obtained results are as follows: Soluble Zr atoms enter only into the Ti-sites of sublattice and increase only the a value of the lattice parameters, while, an increase of Al content increases only the c value. These anisotropic effects of the elements on the lattice parameters are attributed to the fact that covalent-like bonds are formed between the Ti atom layer and the Al layer. A region of a high degree of order shifts from (Ti1-xZrx)Al to Ti-rich side on the high Zr side. This cause is considered to be that Ti atoms play the same role as Al in the high Zr phase. A region of a low degree of order is located on the high Zr and high Al side, which is attributed to the existence of a degenerated ternary compound. The hardness depends not on the axial ratio c/a but on the degree of order. The solution hardening by Zr is observed only when the amount of the addition is small.
intermetallic compound, TiAl(γ) phase, titanium-aluminum-zirconium alloys, hardness, crystal structure, lattice parameter, degree of order, slip system, alloying elements
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