Online Lecture by prof. Klaus-Dieter Liss

Metals under microstructural evolution –
followed in-situ by synchrotron and neutron radiation

Speaker: prof. Klaus-Dieter Liss,  School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, NSW 2522, Australia.

Title:
Metals under microstructural evolution – followed in-situ by synchrotron and neutron radiation

Abstract:
In-situ neutron and synchrotron X-ray diffraction deliver unique insights into the microstructural evolution of metals under exotic conditions, both in-situ and in real-time.
Comprehensive exploitation of scattering signals includes multi-dimensional reciprocal-space studies on a number of individual grains and local information. For each constituting phase, their statistics and temporal behavior reveal information about grain growth or refinement, subgrain formation, static and dynamic recovery and recrystallization, slip systems, and twinning.
Grain orientation correlations can be revealed, and lattice strain gives complementary insight into the transformation and reaction processes upon heating ramps or other in-situ conditions.

Here, I like to focus on microstructural rearrangements in reciprocal space, such as recrystallization and grain growth. In particular, white-beam Laue diffraction reveals the reorientation processes underlying abnormal grain growth in magnesium alloy, which has been predicted to be erratic and without any practical technique to be observe.
In the scenario, some grain boundaries are spontaneously activated, opening diffusion channels for grain rotation until coalescence. During its reorientation, however, the driving forces can take over from many neighboring grains, such that its reorientation is indeed erratic. Once coalesced into a larger grain, their boundaries remain activated, giving rise to further growth.

The findings present the missing puzzle stone of the initiation of abnormal grain growth.

This session was chaired by dr. S.E. Erik Offerman.