Deformation Induced Microstructural Modification: Session II: In Situ Interrogation of Microstructural Evolution During Deformation
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Shaping and Forming Committee
Program Organizers: Arun Devaraj, Pacific Northwest National Laboratory; Suveen Mathaudhu, Colorado School of Mines; Kester Clarke, Los Alamos National Laboratory; Bharat Gwalani, North Carolina State Universtiy; Daniel Coughlin, United States Steel Corp
Monday 2:00 PM
March 15, 2021
Room: RM 38
Location: TMS2021 Virtual
Session Chair: Bharat Gwalani, Pacific Northwest National Laboratory
2:00 PM Invited
Probing Microstructural Evolution in Deformation with Electrons and X-rays: Anthony Rollett1; Robert Suter1; Rachel Lim1; Matthew Wilkin1; Yueheng Zhang1; Patcharapit Promoppatum2; Carter Cocke3; Ashley Spear3; Ricardo Lebensohn4; Jerard Gordon1; 1Carnegie Mellon University; 2KMUTT; 3University of Utah; 4Los Alamos National Laboratory
Synchrotron x-rays are uniquely useful as a probe of microstructural evolution during deformation. A brief update will be given of progress on developing Bragg Coherent diffraction imaging (BCDI) for strain mapping in polycrystalline samples. Also, microstructural evolution in cyclic deformation in Ti-7Al shows general changes in strain (& stress) states with stronger outlier changes in a minority of grains. Preliminary results from an experiment to determine CRSS evolution in a high entropy alloy are reviewed. A recent AFRL Modeling Challenge provided HEDM data for a tensile test of an additively manufactured (AM) superalloy sample: simulating the test with the FFT method showed good agreement for strain tensors from grains selected for their high confidence values. Simulation of laser melting in AM shows that, in addition to residual stress, a small amount of plastic strain can be developed. This is being investigated via orientation mapping in printed metals.
2:30 PM
In Situ Analysis of Microstructural Evolution of Metallic Alloys under High Speed Rotational Shear Deformation: Arun Devaraj1; Tingkun Liu1; Bharat Gwalani1; Matthew Olszta1; changyong Park2; Stanislav Sinogeikin3; Cynthia Powell1; Suveen Mathaudhu4; 1Pacific Northwest National Laboratory; 2High pressure collaborative access team; 3DAC tools; 4University of California Riverside
In order to develop shear-based solid phase processing methods, we aim to better understand the fundamental atomic scale mechanisms of mass and energy transfer in materials under shear deformation. To achieve this aim, we developed a first of its kind synchrotron-based in situ high-energy x-ray diffraction capability using a high-speed rotational diamond anvil cell (HSRDAC). HSRDAC provided time resolved synchrotron-based XRD results on lattice strain evolution and change in spatial variation of shear deformation induced alloying in Cu-Ni alloys. These in situ results were correlated with detailed microstructural characterization before and after shear deformation using transmission electron microscopy and atom probe tomography. This HSRDAC capability can provide new insights into the unique role of shear deformation in formation of metastable states, as well as in modifying the phase transformation pathways in a wide variety of alloy systems.
2:50 PM Invited
Deformation at a Single Precipitate Using a Nanocube Model System: Wendy Gu1; Mehrdad Kiani1; Mitsu Murayama2; 1Stanford University; 2Virginia Tech
Understanding deformation at nano-precipitates is critical to the design of next-generation alloys. The theory of precipitate hardening is based on the interaction of dislocations with ensembles of precipitates. It has been challenging to study the mechanical behavior of dislocations at an individual precipitate experimentally, but is important for the predictive modeling of precipitate strengthened systems. Here, we look study the mechanical behavior of metallic nanocubes that contain individual precipitates with well-defined size, shape and interfacial dislocations. Colloidal synthesis is used to create bimetallic Au@Cu core-shell nanocubes with overall size of ~60-100 nm, and precipitate size of 14 and 24 nm. Nanocubes are compressed inside of a SEM to obtain stress-strain behavior. TEM strain mapping is used to characterize the region around the precipitate. Au@Cu core-shell nanocubes are found to have higher strength, and pronounced strain hardening that we relate to Orowan looping, Orowan stress, back stress and image stress.
3:20 PM
In-situ Analysis of Microscale Deformation and Fracture in Severely Deformed Polycrystalline Tungsten: Lara Draelos1; Zachary Levin1; Ankit Srivastava1; 1Texas A&M University
At room temperature polycrystalline tungsten undergoes intergranular brittle fracture with no appreciable ductility. The brittle fracture of tungsten poses significant hurdles for many applications that would benefit from its other attractive properties such as, high density, high melting temperature and high strength. Recent works have shown that the morphology of grains and texture of polycrystalline tungsten can be tuned to significantly enhance its damage tolerance. Here we have carried out in-situ compression tests of polycrystalline tungsten processed via severe plastic deformation to yield lamellar grain morphology and strong texture. In addition, the effect of relatively low temperature post-process annealing is also considered. Our in-situ tests coupled with microscale digital image correlation allows us to capture both the macroscopic response and the distribution of microscopic deformation and strains. In this presentation we attempt correlate the material microstructure, microscale deformation and strain measurements with the observed macroscopic response of the material.