Mechanical Behavior and Stress-Induced Martensitic Transformation in Nanocrystalline Ti_49.4Ni_50.6 Alloy

Abstract:

Amorphous-nanocrystalline Ti49.4Ni50.6 alloy in the shape of a disc 20 mm in diameter has been successfully produced using high pressure torsion (HPT). Application of HPT and annealing at temperatures of 300–550°C resulted in formation of a nanocrystalline (NC) structure with the grain size (D) about 20–300 nm. The HPT samples after annealing at Т = 400°C with the D= 20 nm possess high yield stress and high ultimate tensile strength (more than 2000 MPa). There is an area of strain-induced transformation B2-B19’ on the tensile curve of the samples with the grain size D =20 nm. The stress of martensitic transformation (σm) of samples is 450 MPa, which is three times higher than σm in the initial coarse-grained state (σm ≈ 160 MPa). The HPT samples after annealing at Т = 550°C with the D= 300 nm possess high ductility (δ>60 %) and high ultimate tensile strength (about 1000 MPa).

• Periodical: Materials Science Forum (Volumes 584-586)
• Pages: 470-474
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.584-586.470
• Online since: June 2008
• Authors: Egor Prokofiev, Dmitriy Gunderov, Alexander Lukyanov, V.G. Pushin, Ruslan Valiev
• Keywords: Mechanical Property, Nanocrystalline (NC) Structure, Severe Plastic Deformation (SPD), Shape Memory TiNi Alloy

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