In situ neutron diffraction study of stresses generated by shape memory alloys

Abstract

In situ neutron diffraction experiments on polycrystalline shape memory alloys/SMA/transforming in thermomechanical cycles were carried out with the aim to learn how to determine stress—strain—temperature responses of SMAs from the in situ neutron diffraction data. Results of a single experiment on NiTi polycrystal deformed in compression at constant temperature are reported. It is found that the macroscopic stress—strain response of the polycrystal can be evaluated from diffraction measured lattice strains (peak position) and integral intensities of a particular well chosen austenite hkl-reflection. The neutron diffraction technique may thus be possibly used to evaluate in situ stress-strain-temperature responses of otherwise inaccessible SMA elements embedded in the smart SMA-composites.

Key Words:

• In situ neutron diffraction
• Shape memory alloy
• Martensitic transformation
• compression—test