Experimental Evidence for Universality of Acoustic Emission Avalanche Distributions during Structural Transitions

Acoustic emission avalanche distributions are studied in different alloy systems that exhibit a phase transition from a bcc to a close-packed structure. After a small number of thermal cycles through the transition, the distributions become critically stable (exhibit power-law behavior) and can be characterized by an exponent $\alpha$. The values of $\alpha$ can be classified into universality classes, which depend exclusively on the symmetry of the resulting close-packed structure.