Mechanical properties of a Cr-Ni-Mo-Al-Ti maraging steel in the process of martensitic transformation

Mechanical properties of a Cr-Ni-Mo-Al-Ti maraging steel are studied experimentally in the process of martensitic transformation. The transformation-start and -finish temperatures are determined from the dilatometric curves under a tensile, compressive or shear hold stress. An anomalous temperature-dependence of the yield stress is investigated. By checking the closing of the dilatometric loop in a full heating-annealing-cooling thermal cycle under the applied hold stress, a back stress is confirmed to exist in both the axial and radial directions in the thin-walled tubular specimen, and its initial value is identified. The annealing condition is proved to have a marked effect on the initial value of the back stress. The back stress is shown to evolve in the progress of transformation. The evolution of the TRIP strain is evaluated under the hold stress in both the axial and shear direction. Especially when the hold stress is removed in the process of transformation, a backflow, due to the Magee effect, is observed.