Experimental study of creep and relaxation of steels at the postcritical stage of deformation

Abstract

The work is aimed at experimental and theoretical study of the regularities and effects of the behaviour of metallic materials at the stage of postcritical deformation, which is of both applied and fundamental interest from the point of view of understanding preceding of the fracture processes and the possibility of predicting the survivability and kinetics of structural failure processes. An experimental assessment was made of the influence of the strain rate in a wide range on the postcritical behaviour of X15CrNi12-2 steel samples at the temperature of 500 °C. Experimental data of rheological processes of the steel at various levels of achieved postcritical deformation was obtained. It was shown that during creep holding at the postcritical stage of deformation, a transition to the final creep stage and subsequent destruction of the samples almost immediately were occurs. An analysis of the experimental dependences obtained during exposition in the relaxation mode demonstrates the independence of the stress level at the end of exposition on the speed of preliminary deformation and, therefore, on the initial value of the stresses, which reached at the beginning of the exposition. The data obtained are necessary to develop models of softening media, taking into account the rheological processes that occur in metallic materials under conditions of postcritical deformation at high temperatures.