Al–Ge–Ti: Phase equilibria and structural characterization of new ternary compounds

•Three partial isothermal sections of Al–Ge–Ti are established.•Crystal structure of three new compounds is investigated.•Partial Scheil diagram and liquidus surface projection are constructed.

Phase equilibria of Al–Ge–Ti have been investigated using scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and differential thermal analysis (DTA). Partial isothermal sections at 400 °C, 520 °C and 1000 °C were obtained with focus on the titanium-poor part up to 50 at.% titanium. Three ternary compounds were found to exist. The compound Al3GeTi (τ1) crystallizes in an own structure type (P4/nmm, tP10). Two structurally closely related compounds were found at the composition Al1−xGe1+xTi: τ2 (0.61 ≤ x ≤ 0.73), Al4Si5Zr3-type, I41/amd, tI  24 and τ2′ (0.36 ≤ x ≤ 0.57), Si2Zr-type, Cmcm, oC12. DTA data were used to construct a ternary reaction scheme (Scheil diagram) up to approximately 1300 °C, a partial liquidus projection and two vertical sections, at 10 at.% Ti and at a constant Al:Ti ratio of 1:1. A total number of 12 ternary invariant reactions were identified.