Microstructural Aspects of Microheterogeneous Deformation and Mechanical Properties of Ni-Ti Based Alloys

¹ Volgograd Architectural Building Academy, Strength of Materials Dep., Akademicheskaya str.1, 400074 Volgograd, Russia
² All-Russia Institute of Light Alloys, Shape Memory Alloys Dep., Gorbunov str. 2, 121596 Moskow, Russia

Abstract

The results of the comprehensive research of the deformation micropicture and mechanical properties of Ni-Ti based alloys are presented. The research of the microheterogeneous deformation on the small bases with the smallest base of 10 micron were made with the help of the elaborated automation method of the deformation measurement in the comparison with different metals. Mechanical properties had been studied on the basis of the deformation diagram research on the results of the deformation measurement with the precision up to 3-10^-5. The distinctive peculiarities of the microheterogeneous deformation of Ni-Ti based alloys were established. The process of the deformation in the microvolumes is extremely heterogeneous. The microheterogeneity of the residual microdeformation distribution is being preserved with the full restoration of the shape under the temperature influence. This explains the difference in mechanical properties of alloys in their proper state and after deformation and restoration of shape. It is shown that deformation of alloys takes place on the account of shifting processes and martensitic transformations. The relation between these micromechanisms of deformations depends on the value of deformation. Heterogeneity of distribution of microdeformation causes the appearance of elastic hysteresis and change of elastisity module in the process of loading and unloading.