The ternary system Al–Ni–Ti Part I: Isothermal section at 900°C; Experimental investigation and thermodynamic calculation

Abstract

Phase relations in the ternary system Al±Ni±Ti have been experimentally established for the isothermal section at 900 C for concentrations 0.1 4 x Al 4 0.7. The investigation is based on X-ray powder diraction, metallography, SEM and EMPA-techniques on about 40 ternary alloys, prepared by argon-arc or vacuum-electron beam melting of proper elemental powder blends. The existence of four ternary compounds, t 1 to t 4 , is con®rmed, however, in contrast to earlier investigations at signi®cantly dierent compositions and with dierent shape of the homogeneity regions. This is particularly true for the phase regions of t 3-Al 3 NiTi 2 with the MgZn 2-type structure ranging from Al 30 Ni 28 Ti 42 (composition lowest in Al) to Al 50 Ni 16 Ti 34 (composition richest in Al) and for t 2-Al 2 NiTi. The complex atom site substitution mechanism in t 3 changing from Ti/Al exchange at Al-poor compositions towards Ni/Al replacement for the Al-rich part was monitored in detail by quantitative X-ray powder diraction techniques (Rietveld analyses). In contrast to earlier reports, claiming a two-phase region Ni{Al x Ti 1-x } 2 +t 3 , we observed two closely adjoining three-phase equilibria: a 2-AlTi 3 +Ni{Al x Ti 1-x } 2 + t 4-AlNi 2 Ti and a 2-AlTi 3 +t 3-Al 2 NiTi 2 +t 4-AlNi 2 Ti. The earlier reported ``homogeneous phase at Al 23 Ni 26 Ti 51 H '' was shown by high resolution microprobe and X-ray diraction measurements to be an extremely ®negrained eutectic. The experimental results are in ®ne agreement with the thermodynamic calculation.

First-Principles Investigations of the Structural, Anisotropic Mechanical, Thermodynamic and Electronic Properties of the AlNi2Ti Compound

“…It can be seen that the lattice parameters at 0 K in this study are close to other theoretical and experimental data [22,35,36,[47][48][49][50][51][52][53][54]. The average deviation of results in this work to references for lattice parameters is less than 1%.…”

“…data in [47]; f Exp. data from [48]; g Data calculated from the selected area electron diffraction pattern in [22]; h Exp. data from [49]; i Data from handbook [50]; j Exp.…”

The Heusler Phase Ti25(Fe50 − x Ni x )Al25 (0 ≤ x ≤ 50); Structure and Constitution

“…[6,12,19,25,26] On the other hand, atom substitution in binary alloys can drastically increase the transition temperature to enlarge the range of the Heusler phase, specifically, in binary Fe 3 Al with BiF 3 -type structure and/or in ternary MnCu 2 Al-type by substitution of Al by Si [27] or of Fe by M (M = Ti, [4,16] V, Cr, Mn, and Mo [26,28] ), respectively. For the ternary alloys, TiFe 2 Al and TiNi 2 Al, past efforts focused on physical properties, [3,8,11,12,[29][30][31] lattice parameters, [6,19,[32][33][34][35][36][37][38][39][40] and structure evaluations. [36] However, no investigation is known dealing with detailed atomic site preference in the Heusler phase of the quaternary system Ti-Fe-Ni-Al.…”

Property-Control of TiNi System Intermetallics and Their Characteristics

“…In contrast, TiNi-12Cu or TiNi-12Al had also B19 type structure or both AlNi 2 Ti and Ti 2 Ni phases, respectively, in addition to B2. Three phases of B2, B19 0 and Ti 2 Ni were identified on TiNi-4.5Al at the room temperature, although this composition showed the mono phase of B2 at 1273 K. 37) For Ti-50Ni, TiNi-1Cr, TiNi-5Cr, TiNi-1.5Fe, TiNi12Cu, TiNi-12Al and TiNi-0.5Re alloys, their homogeneously heat-treated microstructures are shown in Fig. 7, their grain sizes are 105, 90, 75, 90, 120, 85 and 60 mm respectively.…”