Growth kinetics of an athermal martensitic transformation by time-resolved optical diffraction from a Ni ₆₃AI ₃₇ (001) surface

Abstract
The vertical and lateral growth process of single martensitic bands on the (001) surface of a Ni ₆₃Al ₃₇ single crystal was investigated using time-resolved diffraction of He-Ne laser light. Our extended kinephotometric setup provided spatial information through an analysis of the Fraunhofer pattern created by diffraction from the surface relief, while temporal resolution was achieved with a fast-response photodiode. On continuous cooling through the martensitic phase transition at a rate of 10 K/min, discontinuous changes in the diffraction pattern occurred on time scales ranging from 100 microseconds up to some tens of milliseconds. Each change in the pattern corresponded to a burst-like upheaval of the relief by a few hundred nanometers. The bands were fully developed within 150-250 ms and reached final heights of about 1.5  m.