Atomic ordering in TiVAl shape memory alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 1991-02, Vol.132, p.237-244
• Main Authors: Lee Pak, J.S., Lei, C.Y., Wayman, C.M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Metals. Metallurgy; Physics; Structure of solids and liquids; crystallography
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/0921-5093(91)90380-6

Newly developed TiAlV shape memory alloys have been investigated in detail to determine the origin of shape memory effects. The crystal structure identification and microstructure observations of Ti15.4V4.0Al and Ti16.1V4.0Al alloys (in weight per cent) have clearly revealed that a martensitic transformation in the Ti15.4V4.0Al alloy occurs during quenching from an ordered tetragonal phase (denoted β 1) to an ordered face-centered orthorhombic (f.c.o.) phase (denoted β 1′). This finding is significant in order to understand shape memory behavior in titanium-based alloys since these alloys are all reported in previous literature to have disordered parent and martensite phases. The volume change associated with the tetragonal-to-f.c.o. transformation is small. This small volume change coupled with the structural ordering found in the present alloys are considered to be primary reasons for why titanium-based alloys show shape memory behavior.