Intermittent plasticity in individual grains: A study using high energy x-ray diffraction

What did the Scientists Discover? 

A metal component is polycrystalline, composed of many crystals or grains. At the scale of millimeters, the deformation of a metal appears to proceed smoothly, whereas at the microscopic scale the underlying processes occurring in individual grains proceed in fits and starts.  In this collaboration between researchers at Cornell University, the University of Illinois at Urbana-Champaign, the Air Force Research Laboratory and the Advanced Photon Source of Argonne National Laboratory, a high-speed detector was used to study these microscale deformation bursts in a grain-by-grain manner.

Two alloys were studied, one titanium alloy and the other magnesium based.  Distinct and isolated bursts of deformation were observed in grains of the titanium alloy, with these events varying considerably in magnitude.  In contrast, while discrete deformation events were observed in the magnesium alloy, the size of these localized deformations did not vary so much and were relatively mild.  The results suggest that existing models for metal deformation may be applicable for many alloys, like the magnesium alloy studied. However, for other complex structural alloys -- used in demanding applications like aerospace -- deformation models can be advanced to better account for action at the grain-scale using data acquired by a high-speed detector.

Impact:

As metallic alloy systems become more complex, and demands for light-weighting, efficiency, performance and safety increase, it becomes necessary to advance engineering fundamentals to consider the microscale behavior as part of the design process.

Collaborators:

Armand Beaudoin, Mechanical Science & Engineering, University of Illinois and Cornell High Energy Synchrotron Source, Cornell University

K. Chatterjee, Mechanical Science & Engineering, University of Illinois

D. Pagan, Cornell High Energy Synchrotron Source, Cornell University

P. A. Shade, Materials and Manufacturing Directorate, Air Force Research Lab

H.T. Philipp, Laboratory of Atomic and Solid State Physics, Cornell University

M.W. Tate, Laboratory of Atomic and Solid State Physics, Cornell University

S.M. Gruner, Cornell High Energy Synchrotron Source, Laboratory of Atomic and Solid State Physics, Kavli Institute for Nanoscale Science, Cornell University

P. Kenesei, Advanced Photon Source, Argonne National Lab

J.-S. Park, Advanced Photon Source, Argonne National Lab

Publication citation:

Chatterjee, K., Beaudoin, A., Pagan, D.C., Shade, PA, Philipp, H.T., Tate, M. W., Gruner, S.M., Kenesei, P., Park J.-S. "Intermittent Plasticity in individual grains:  A study using high energy x-ray diffraction," Structural Dynamics 6(1):014501.  January 2019. DOI: 10.1063/1.5068756

Funding: