Structure and phase transformations in TiNiFe ternary alloys subjected to plastic deformation by high-pressure torsion and subsequent heat treatment

• Published in: Physics of metals and metallography Vol. 115; no. 4; pp. 365 - 379
• Main Authors: Pushin, V. G., Kourov, N. I., Kuranova, N. N., Pushin, A. V., Uksusnikov, A. N.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.04.2014; Springer; Springer Nature B.V
• Subjects: Alloys; Annealing; Chemistry and Materials Science; Crystals; Degassing of metals; Diffraction; Diffusion; Dislocations; Electric properties; Heat treatment; Martensitic transformations; Materials Science; Metallic Materials; Metals; Nanostructure; Phase Transformations; Plastic deformation; Specialty metals industry; Structure; Ternary alloys; Torsion; X-rays; thermoelastic martensitic transformations; recrystallization; high-pressure torsion; crystallization; titanium nickelide; megaplastic deformation; annealing
• ISSN: 0031-918X; 1555-6190
• DOI: 10.1134/S0031918X14040127

The results of a complex study of ternary TiNiFe alloys with a low-temperature shape-memory effect subjected to megaplastic deformation by high-pressure torsion (HPT) with subsequent heat treatment are presented. Investigations have been performed using X-ray diffraction, transmission and scanning electron microscopy, and measurements of electrical properties. It has been established that, at moderate degrees of reduction, the plastic deformation in the Ti 50 Ni 49 Fe 1 alloy induces a B 2 ↔ B 19′ thermoelastic martensitic transformation and the formation of a developed banded dislocation and twin structure in the B 19′ martensite; in the Ti 50 Ni 47 Fe 3 alloy, a mainly analogous dislocation substructure is formed, but in the B 2 austenite. The megaplastic deformation by HPT at room temperature leads to the amorphization of the Ti50Ni49Fe1 alloy and to the high-angle nanofragmentation of the Ti50Ni47Fe3 alloy. Specific features of the evolution of the structure and martensitic transformations in the TiNiFe ternary alloys after plastic deformation and heat treatment have been established. It has been found that the heat treatment of both alloys after HPT at temperatures of 553–773 K results in the formation of a nanocrystalline or mixed nano-submicro-crystalline structure.