The shape memory effect and superelasticity are usually found in alloys exhibiting spontaneous martensitic transformation. Thus it is hard to imagine that such interesting effects can appear in a system without a martensitic transformation. In this Letter we show shape memory and the superelasticity effect in a nonmartensitic Ti48.5Ni51.5 alloy, which has no martensitic transformation but undergoes a "strain glass" transition. In situ x-ray diffraction experiment showed that the shape memory and superelasticity in strain glass stem from a stress-induced strain glass to martensite transformation and its reverse transformation. The new shape memory and superelasticity in strain glass extends the regime of the shape memory effect and superelasticity and may lead to novel applications.

A recent study has indicated that there exists a different class of glass, the strain glass, in the nontransforming composition regime of Ti-Ni alloys. However, the critical proof for a glass, the evidence for the nonergodicity in the glassy state, has been missing in this system. By a zero-field-cooling/field-cooling measurement of static strain, we show experimentally that the ergodicity of the frozen strain glass is indeed broken. The creep measurement clearly shows the slowing down of kinetics upon strain glass transition. These features are physically parallel to other well-known glasses such as cluster-spin glasses and ferroelectric relaxors; thus, we introduce the notion of a ferroic glass and suggest a common underlying physics.

A new method for the determination of clay swelling thermodynamics from computer simulation is discussed and evaluated. This method allows for the determination of temperature, pressure, and water chemical potential dependence of clay swelling from simulations at a single thermodynamic state point. The temperature dependence and pressure dependence of clay swelling are shown to be directly related to the composite system entropy and volume change, respectively, that accompany swelling. Expressions for the chemical potential dependence of clay swelling are used to determine constant pressure layer spacing and adsorption isotherms, quantities that are well suited for comparison with experimental measurements. This method is evaluated through grand isoshear ensemble simulations of Na-montmorillonite, a prototypical swelling clay. Approximations associated with all expressions are discussed with explicit calculations used to demonstrate their regimes of validity.