STRESS- AND STRAIN-DRIVEN MARTENSITIC TRANSITIONS: AN ACOUSTIC EMISSION STUDY IN SINGLE-CRYSTALLINE Cu-Zn-Al

摘要

We report on experiments aimed at comparing stress-strain trajectories under stress- and strain-driven conditions in a Cu-Zn-Al single crystal undergoing a martensitic transition. In the strain-driven case the transition is constrained by the externally imposed length which yields re-entrant behaviour related to retransformation effects. In contrast, when the transition is stress-driven shape-changes are not constrained and thus the strain is free to fluctuate. We show that this different behaviour is reflected in the acoustic emission generated during the transition. In particular, for stress-driven trajectories we were able to show that the acoustic emission associated with the free motion of an interface is proportional to its average velocity.