$crystaldiffract manual$

$crystaldiffract manual$

Nishiyama, Martensitic Transformation ( Elsevier, 2012). Wayman, Shape Memory Materials ( Cambridge University Press, 1999). Shape memory alloys (SMAs) are functional materials characterized by their specific properties of shape memory and superelastic effects, which are based on a reversible first order diffusionless structural phase transition, called martensitic transformation (MT), taking place between the high temperature phase, austenite, and the low temperature phase, martensite, via an atomic lattice shearing responsible for the change of shape.

$crystaldiffract manual$

The neutron experiments have allowed a complete description of the strains during martensitic transformation, and the obtained conclusions can be extrapolated to other SMA systems. In addition, the thermal expansion coefficients of both martensite and austenite phases were measured. The observed effects and the measured strain relaxations are in agreement with the predictions of the model proposed to explain this behavior in previous calorimetric studies. The evolution of the stresses is measured through the strain relaxation, which is accessible by neutron diffraction. These changes are associated with the relaxation of the mechanical stresses elastically stored around the martensitic variants, due to the different self-accommodating conditions after uncompleted transformations. Two different effects are observed, the d-spacing position shift and the narrowing of various diffraction peaks, along uncompleted transformation cycles during the thermal reverse martensitic transformation.

$crystaldiffract manual$

A careful study of the influence of partial cycling on the neutron diffraction spectra in the martensitic phase is presented. This work is focused on the analysis of the strain evolution along the temperature memory effect appearing in these alloys after partial thermal transformations. In situ neutron diffraction is used to study the strain relaxation on a single crystal and other powdered Cu-Al-Ni shape memory alloys (SMAs) around martensitic transformation temperatures.

$crystaldiffract manual$

Crystaldiffract manual