Acoustic emission related to the properties of copper-aluminium martensite

The martensitic transformation in a beta phase, Cu=12 wt.% Al alloy was studied by three different techniques; acoustic emission (AE), electrical resistivity (R), and electron microscopy. By changing the heat treatment it was possible to change the size of the ordered domains, and consequently both AE ringdown counting (N) and the hardness number (H) of the martensite were strongly increased, H and N were found to be related by the equation N=(0.042H-12.28)*106 counts. Amplitude analysis of the AE bursts showed that increasing the size of the ordered domains increases the amplitude of bursts and the number of ringdown counts, while the number of bursts is constant since the number and average size of plates are the same, as shown from transmission electron micrographs.