S. Miura

Pseudoelasticity in Au-Cd thermoelastic martensite

Abstract Thermoelastic martensitic transformation has been studied by the analysis of stress-strain curves in binary Au-Cd alloys, containing 46·5, 47·5, 48·5, 49, 49·5, and 50 at. % Cd, respectively. The pseudoelastic characteristics, i.e. superelastic and ferroelastic behaviour upon tension compression test and that the origin of the shape memory effect bears a close relation to the ferroelastic loop, have been explained on the basis of the lattice softening, that is. the shear elastic constant, C′ = (C11-C12)/2, decreases toward zero in the vicinity of the transition temperature. In particular the critical condition for obtaining the ferroelastic loop can be experimentally determined by assuming a critical stress, which is termed ‘ferroelastic limit’. The ferroelastic limit may depend upon the elastic anisotropy of alloys and lies in the region 6 Kg/mm- in the Au-Cd alloy.

Ferroelasticity and memory effect in the β-phase alloys

Abstract Ferroelastic behavior in the stress-strain curve has been found in the β-AuCd and AuCuZn alloys, which involves the origin of ‘memory effect’.

Pseudoelastic behavior and its strain rate dependence in thermoelastic In-Tl martensite

Experimental results are reported for single crystals of In-21 and 22 at. percent Tl alloys: (1) The superelastic behavior associated with the Martensitic transformation, shape memory effect, and superelasticity in the martensite phase. (2) The strain rate dependence of the pseudoelastic behavior in the Martensite phase.

Pseudoelastic behaviour associated with thermoelastic martensitic transformation in an Au52.5 x Ag x Cd47.5 pseudobinary alloy

Abstract The relation between pseudoelastic behaviour and the thermoelastic martensitic transformation has been studied by means of the measurement of stress–strain curves in the temperature range above and below the martensitic transition temperatures in an Au52.5− x AgxCd47.5 pseudobinary β–phase alloy. It is of special interest that the so–called superelastie loops accompanying two–stage yieldings in stress–strain curves were observed just above M8 , (the martensite–start temperature on cooling). These are thought to be due to successive formation of martensite phases. In conjunction with the measurements of heat capacity and of electrical resistivity, the thermoelastic martensitic properties of the present alloys are discussed from a thermodynamic point of view.