Crystallographic characterization of pseudoelastic phase transformation in Cu–13.1Al–4.0Ni (wt.%) single crystal high temperature shape memory alloy using neutron diffraction

Abstract

This paper reports neutron diffraction experiments on high temperature Cu–13.1Al–4.0Ni (wt.%) shape memory alloy single crystals. The Cu–13.1%Al–4%Ni (wt.%) single crystal wires having nominal dimensions of 2.0 mm (diameter) and 100 mm (length) were subjected to tensile load at room temperature and at 175°C (well above the austenitic finish temperature). Diffraction patterns were acquired at various stress levels. The growth and decay of different variants during the (β¹₁ 18R monoclinic martensite reorientation under load were identified. Neutron diffraction results at 175 and 200°C were used to study the biased martensitic variant formation during the (β₁) cubic austenite to (β¹₁) 18R monoclinic martensite transformation under load. The observed results are correlated with stress-overall strain data obtained from experiments carried out at different test temperatures in an Instron machine with a high temperature environmental chamber.