Crystallographic characterization of pseudoelastic phase transformation in Cu–13.1Al–4.0Ni (wt.%) single crystal high temperature shape memory alloy using neutron diffraction
Affiliations: Smart Materials and MEMS Laboratory, Department of Applied Science, University of Arkansas at Little Rock, 2801 South University, ETAS 575, Little Rock, AR 72204-1099, USA | Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA | Department of Solid State Physics, Ioffe Physico-Technical Institute, St. Petersburg, Russia
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.
Keywords: CuAlNi single crystal, In situ neutron diffraction, Phase transformation, Stress-temperature phase diagram
