Tensile Flow Behavior of 9Cr–2WVTa Reduced-Activation Ferritic/Martensitic Steel

Tensile flow behavior of 9Cr–2WVTa ferritic/martensitic (RAFM) steel in normalized-tempered condition has been studied based on Voce equation over the temperature range of 25–600 °C. Yield strength (YS) and ultimate tensile strength (UTS) decrease with increase in temperature. However, the elongation decreases with increase in temperature up to 400 °C and then increases beyond 400 °C. True stress–true plastic strain curves at all temperatures are adequately described by the Voce equation. While saturation stress (σs) decreases with temperature, the rate at which the stress approaches the saturation value (nV) increases with temperature. The variation of the stress increment up to saturation stress (σun) with temperature shows a plateau in the temperature range of 200–400 °C. Moreover, the product of σun and nV (σun·nV) is inversely proportional to the elongation. The relation of elongation to σun·nV can be described by a power law with the exponent of −1.63.

Unified Tensile Work Hardening Behaviour of Thin Section Plate and Forged Thick Section 9Cr-1Mo Ferritic Steel

Detailed investigation has been performed on tensile work hardening behaviour in terms of the variations of instantaneous work hardening rate (θ = dσ/dεp, where σ is true stress and εp is true plastic strain) with stress and true plastic strain rate (ε̇p) for temperature range 300–873 K in two different material conditions, (i) normalised and tempered plate and (ii) quenched and tempered tubeplate forging of 9Cr-1Mo ferritic steel. Both plate and tubeplate forging exhibited two-stage work hardening and three different temperature regimes in the variation of θ with σ. The variations of θ with respect to ε̇p exhibited unified work hardening in terms of a single master curve independent of temperature and initial microstructure. θ varied linearly with reciprocal of plastic strain rate, i.e. 1/ε̇p, and as a consequence, linear correlation between the rate of change of true stress and true plastic strain rate independent of temperature and microstructure has been obtained.

Strain-Resistivity Behavior of a Ti-45Ni-5Cu Shape Memory Alloy during Superelastic and SATWME Cycling

The strain-resistivity behavior of Ti-45.0Ni-%.0Cu wires has been measured during superelastic cycling. The results are in good agreement with previous results, showing that the main changes of resistivity during superelastic cycling are due to Austenite ↔ Martensite phase changes and anisotropic variant orientation. The true plastic strain (dislocations) does not seem to play an important role for this alloy.