Affiliation:
1. Siberian Physical Technical Institute, National Research Tomsk State University, Lenin Ave. 36, 634050 Tomsk, Russia
Abstract
Hydrogen’s effect on the shape memory effect (SME) of [1¯17]-oriented Ti49.7-Ni50.3 (at.%) alloy single crystals, with a B2–B19′ martensitic transformation (MT), was studied after being electrolytically hydrogenated at a current density of 1500 A/m2 for 3 h at room temperature under isobaric tensile deformation. It was shown that, under the used hydrogenation regime, hydrogen was in a solid solution and lowered the elastic modulus of B19′ martensite. The hydrogen in a solid solution increased (i) the yield strength σ0.1 of the initial B2 phase by 100 MPa at Md temperature, (ii) the σ0.1 of the stress-induced B2–B19′ MT by 25 MPa at Ms temperature, and (iii) the plasticity of B19′ martensite relative to the hydrogen-free crystals. At the same level of external stresses, the SME in the hydrogenated crystals was greater than that in hydrogen-free crystals. At external tensile stresses σex = 200 MPa, the SME was 4.4 ± 0.2% in the hydrogenated crystals and 1.8 ± 0.2% without hydrogen. Hydrogen initiated a two-way SME of 0.5 ± 0.2% at σex = 0 MPa, which was absent in the hydrogen-free crystals. The physical reasons leading to an increase in the SME upon hydrogenation are discussed.
Funder
Decree of the Government of the Russian Federation
Tomsk State University Development Programme
Subject
General Materials Science,Metals and Alloys
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