STATISTICS OF AVALANCHES IN MARTENSITIC TRANSFORMATIONS .1. ACOUSTIC-EMISSION EXPERIMENTS

We present an experimental study of the transformation avalanches taki ng place during a thermally induced thermoelastic martensitic phase tr ansition of a Cu-Zn-Al alloy. We have studied the statistical distribu tion of amplitudes and durations of the acoustic emission signals rele ased in the avalanches and found them to exhibit power-law behavior in more than one decade. Distributions measured around different tempera tures along the transformation path are found to be equivalent. We hav e measured the exponents for the distribution of amplitudes (alpha = 3 .6 +/- 0.8) and durations (tau = 3.5 +/- 0.8), for the statistical dep endence of amplitudes on durations (x = 1.0 +/- 0.1) and for the power spectrum of trains of measured acoustic signals (phi = 0.9 +/- 0.1).