Crystal rotation during alloy heating

TL;DR

This study visualizes unexpected crystal rotation during alloy heating using in situ 3DXRD microscopy, revealing its relation to residual strain relief and thermal effects, thus advancing understanding of microstructural dynamics during heating.

Contribution

First visualization of crystal rotation during alloy heating with in situ 3DXRD microscopy, linking it to residual strain relief and thermal effects.

Findings

Crystal rotation occurs during alloy heating, related to residual strain relief.

Intermittent diffraction spot dynamics are linked to thermal expansion and crystal distortion.

Residual strain analysis and simulations elucidate strain relief mechanisms during heating.

Abstract

Over past decades, high energy X-ray diffraction techniques at synchrotron beamline offer us the unique possibility to follow concomitantly some mechanisms on the grain level in metallic materials. Crystal rotation, as one important factor for the crystal orientation distribution, usually influences the anisotropic properties of materials. Crystal rotation has been visualized in deformation, recrystallization, and chemical reaction processes. In this study, we firstly visualized an unexpected crystal rotation during heating up of superalloys as well by in situ 3DXRD scanning microscopy which has not been previously reported yet. The crystal rotation was found to be related to the locked-in first order residual strain relief during the annealing treatment. In addition, intermittent dynamic, i.e., some individual diffraction spots from Debye-Scherrer rings appearing, disappearing, and reappearing, occurred in this study which has ever been thought to be caused by subgrain formation in deformation experiments. However, by residual strain analysis coupled with finite element simulation, we found that the intermittent dynamic is married with thermal expansion, crystal distortion, and crystal rotation as well. This finding opens a new world for deeply understanding the residual strain relief during materials, particularly metal, heating.