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

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 degrees C (well above the austenitic finish temperature). Diffraction patterns were acquired at various stress levels. The growth and decay of different variants during the (beta(1)(1)) 18R monoclinic martensite reorientation under load were identified. Neutron diffraction results at 175 and 200 degrees C were used to study the biased martensitic variant formation during the (beta(1)) cubic austenite to (beta(1)(1)) 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.