Real-time analysis of martensitic phase transition of cobalt

Professor K. F. Ludwig (Boston University, USA) and his colleagues have recently reported their real-time X-ray scattering studies on heterogeneous microscale dynamics in the martensitic phase transition of cobalt. During the transformation of the high-temperature fcc phase to the low-temperature hcp phase, first, a rapid local transformation happens, and then, strains are relaxed slowly. The research group employed coherent X-ray scattering measurements to see the latter part of the transformation. It was found that the kinetics is dominated by discontinuous sudden changes - avalanches. The spatial size of observed avalanches varies widely, from 100 nm to 10μm, the size of the X-ray beam. For more information, see the paper, "Direct Measurement of Microstructural Avalanches during the Martensitic Transition of Cobalt Using Coherent X-Ray Scattering", C. Sanborn et al., Phys. Rev. Lett. 107, 015702 (2011).