Role of martensite transformation in variation of physicomechanical properties of Nb-Ti (45 and 50 wt% Nb) alloys at low temperatures

Abstract The structural state of Nb-Ti (45 and 50 wt% Nb) alloys after thermomechanical treatment (TMT), and the influence of TMT on their mechanical properties, plastic deformation characteristics and electrical resistance are studied in the temperature range 295–4.2 K. It is shown that the direct and reversible β ⇌ α ″ transformation, which proceeds orientationally, leads to: 1, anomalous temperature dependences of the relative elongation, proportionality limits and yield strength of hardened and drawn samples at 160-77 K, the degree of anomaly being dependent on the TMT; 2, pseudo-elasticity in the stress-strain curves σ ( Δl ), the temperature range of the pseudo-elasticity being dependent on the TMT; and 3, non-monotonous behaviour in the strain dependences of electrical resistance ρ ( Δl ) and stress σ ( Δl ) in all structural states.