Find in Library

The mechanical properties of Ti_49.8Ni_50.2 (at %) alloy under tension at room temperature are studied in dependence on the true strain (<i>e</i> = 1.84–9.55) specified during isothermal multi-axial forging (abc-pressing). It was found that the stress at the beginning of the pseudoyield plateau does not depend on the value of the true abc-strain. It was found that after abs-pressing, already at a true strain <i>e</i> = 1.84, the yield stress σ_y was 900 ± 25 MPa, which is more than twice as high as compared to σ_y in the initial state of the specimens. With a further increase in the abc-strain, the yield stress continues to increase slightly and reaches 1000 ± 25 MPa at <i>e</i> = 9.55. In this case, the ultimate tensile strength of the samples increases by about 15%. The strain-hardening coefficient ϴ = dσ/dε at the III (linear) stage of the σ(<i>ε</i>) curve has a similar dependence on <i>e</i>. It is shown that after abc-pressing with <i>e</i> from 1.84 to 9.55, the yield stress and ultimate tensile increase linearly with increasing <i>d</i>^−1/2 in accordance with the Hall–Petch relation, where <i>d</i> is the average grain–subgrain size.