Reversible effect of memory of form as the result of thermal cycling conditioning under load

Abstract

1. The amount of the REMF formed as the result of thermal cycling under load is not proportional to the residual deformation, which is a violation of the known rule valid in the case of isothermal loading. 2. The amount of the REMF depends substantially upon the number of preliminary thermal cycles under load. With the same amount of plastic deformation the greater the number of thermal cycles, the greater the effect. Such an influence of repeated martensite⇌austenite transformations may be explained by features of the processes of inheritance of defects of the crystalline lattice in the martensite transformations. 3. Thermal cycling treatment of titanium nickelide-base alloys under the action of an external load may lead to the occurrence of two REMF's of opposite signs. The possibility of their coexistence and interaction must be taken into consideration both in interpretation of the experimental results and in prediction of the mechanical behavior of parts of various devices. 4. After thermal cycling with significant stresses the spontaneous change in form of the material may have a complex character accompanied by a change in the direction of deformation with a steady reduction or increase in temperature.