Study of viscoelastic transition in heat-resistant polycrystalline alloy VZhl71 of the Ni - Co - Cr system

Abstract

Heat-resistant materials used, for example, in aircraft parts, are exposed to high temperatures and are heated under the impact of variable external forces. At a certain point in time, the material that first experienced a small deformation ceases to be simply elastic and graduates into a viscoelastic state. Microyield thus developed in the material, subsequently leads to the creep. We present the results of studying the microyield in a heat-resistant polycrystalline alloy VZhl71 of the Ni - Co - Cr system. A high-temperature background of the internal friction was studied by mechanical spectroscopy. It is shown that the transition of the alloy from an elastic to a viscoelastic state proceeds in two stages and is accompanied by microyield resulted from the dislocation movement. The first and second activation energies of the high-temperatureinternal friction background are determined for the state of the material under consideration. An expression for calculating the transition temperature is derived. The results obtained can be used in the study of the states of heat-resistant, high-temperature and structured materials, as well as amorphous metals and alloys.