Advanced Solid Phase Processing Symposium: Fundamental Deformation Mechanisms
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Mechanical Behavior of Materials Committee, TMS: Shaping and Forming Committee
Program Organizers: Suveen Mathaudhu, Colorado School of Mines; Cynthia Powell, Pacific Northwest National Laboratory; Kester Clarke, Los Alamos National Laboratory; Anthony Reynolds, University of South Carolina; Mostafa Hassani, Cornell University

Monday 2:30 PM
February 24, 2020
Room: Balboa
Location: Marriott Marquis Hotel

Session Chair: Anthony Reynolds, University of South Carolina; Bharat Gwalani, Pacific Northwest National Laboratory


2:30 PM  Invited
Phase Transformations Induced by Large Plastic Deformations under High Pressure: Four-Scale Theory and in Situ Experiments: Valery Levitas1; 1Iowa State University
    Superposing large plastic shear on high pressure in rotational diamond anvil cell (RDAC) leads to numerous new phenomena, including drastic reduction in phase transformation (PT) pressure and appearance of new phases. Here, recent advances in our four-scale theory, corresponding simulations, and in situ XRD experiments for plastic strain induced PTs will be presented. Atomic simulations were used to determine crystal lattice instability conditions under action of all six components of the stress tensor. At the nano- and microscales, coupled evolution of PT and dislocations is studied utilizing developed nano- and microscale phase field approaches, leading to microscale kinetic equation. This equation is utilized in the large-strain macroscopic theory for coupled PTs and plasticity. At the macroscale, the behavior of the sample in RDAC is studied using finite element approach. The obtained results offer new understanding of strain-induced PTs under pressure and methods of controlling PTs and searching for new phases.

2:55 PM  Invited
Plastic Flow Instability, Surface Folding and a Mechanochemical Effect in Large Strain Deformation of Metals: Srinivasan Chandrasekar1; Anirudh Udupa1; Tatsuya Sugihara2; Koushik Viswanathan3; James Mann4; 1Purdue University; 2Osaka University; 3Indian Institute of Science; 4University of West Florida
    Utilizing high-speed in situ imaging and a model 2-D deformation system, we explore evolution of plastic flow at surfaces in large strain deformation of highly strain-hardening metals. We demonstrate the occurrence of a plastic buckling stability that triggers a highly redundant flow mode - sinuous flow - characterized by large-amplitude folding and large energy dissipation. Key features of the sinuous flow field and buckling are elucidated, quantitatively. We show that the sinuous flow can be suppressed and replaced by a much more favorable (low-energy) flow mode, by application of very thin surface-active films that effect a local ductile-to-brittle transition in the deformation. Implications of this mechanochemical effect for cutting and deformation processing of metals, and for environmentally-assisted cracking are discussed.

3:20 PM  
Multimodal Analysis of Microstructural Evolution of Metallic Alloys under Shear Deformation: Arun Devaraj1; Bharat Gwalani1; Tamas Varga1; Changyong Park2; Luciano Bergmann3; Jorge Santos3; Peter Staron3; Benjamin Klusemann3; Tiffany Kaspar1; Peter Sushko1; Suveen Mathaudhu1; Cynthia Powell1; 1Pacific Northwest National Laboratory; 2High Pressure Collaborative Access Team; 3Helmholtz-Zentrum Geesthacht
    In order to develop shear-based solid phase processing methods for achieving bulk nanostructured metallic alloys, 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 employed synchrotron-based in situ and ex situ high-energy x-ray diffraction capabilities under high pressure, with or without shear deformation. We used a diamond anvil cell, as well as the FlexiStir in-situ friction stir and processing system. The obtained synchrotron-based XRD results were correlated with detailed microstructural characterization before and after shear deformation using transmission electron microscopy and atom probe tomography. Our results on shear induced structural and chemical modifications of several model metallic alloys such as Al-Si, Cu-Nb and Cu-Ni provide new insights on the potential role of shear deformation in formation of metastable states, as well as in modifying the phase transformation pathways of these alloy systems.

3:40 PM  
Strain in Friction Extrusion: Tony Reynolds1; Md. Reza-E-Rabby2; Xiao Li2; Komarasamy Mageshwari2; Jeffrey Holliday1; 1University of South Carolina; 2PNNL
    Previous work has demonstrated the ability to measure redundant strain components in friction extruded wires using marker materials and mechanical tomography. However, relationships between the primary process parameters, die rotation rate, extrusion rate/force, die geometry, and imposed strains are poorly understood. In this presentation, results of an extensive marker study of strain imposed during friction extrusion will be presented. Total strains have been measured using markers deforming compatibly with the matrix under several different extrusion conditions. Extrusions were performed under extrusion rate control and process responses including extrusion force, torque, and temperature are measured along with the strain.

4:00 PM Break

4:20 PM  Invited
Hybrid Cutting-Extrusion for Sheet Metal Production with Exceptional Microstructure Control: Kevin Trumble1; B. Stiven Puentes1; Mohammed Issahaq1; Mojib Saei1; Anirudh Udupa1; James Mann2; Srinivasan Chandrasekar1; 1Purdue University; 2University of West Florida
    Machining-based processes for sheet and foil production via large-strain deformation are under development at Purdue University. A hybrid cutting-extrusion (HCE) process imposes highly confined shear with intense adiabatic heating and high hydrostatic pressure for direct production of sheet at high rates in a single stage of deformation. Unlike rolling, the total strain is imposed all at once and is controllable independent of sheet thickness. The process enables sheet production in alloys of low workability that are challenging to produce economically by rolling, while offering microstructure control ranging from severe plastic deformation structures to dynamic recrystallization, and unique shear textures. Recent progress in scaling up the process using a 50-HP lathe will be highlighted, along with application to high-silicon electrical steels of low workability. Surface quality, microstructure and texture development in electrical steels, as well as aluminum alloys and brass, will be discussed.

4:45 PM  
Microstructural Analysis and Modeling of Grain Refinement During Tribometric Surface Deformation: Aashish Rohatgi1; Yulan Li1; Bharat Gwalani1; Shenyang Hu1; Yang He1; Arun Devaraj1; Erin Barker1; Tiffany Kaspar1; Jinhui Tao1; Chongmin Wang1; Petr Sushko1; Suveen Mathaudhu2; 1Pacific Northwest National Laboratory; 2University of California Riverside
    The goal of this work is to understand and model the microstructural evolution in the sub-surface region of metals and alloys under surface shear deformation. Pure Al and cast Al-Si alloy were selected as model materials and subjected to repeated surface shear using a pin-on-disk type linear reciprocating tribometer. The resulting sub-surface microstructure was analyzed using optical and electron microscopy and analytical techniques and was observed to undergo significant grain-size refinement. A model combining FFT-based crystal plasticity (CP) and phase field method (PFM) was developed to simulate the microstructural evolution - The CP simulations determine the dislocation density distribution and stored energy resulting from plastic deformation while the PFM is used to model grain refinement and evolution under plastic strains. The results of this work will provide insights into mechanisms associated with unique microstructures and properties that are often observed in materials subjected to solid phase processing.

5:05 PM  
Structural and Compositional Changes During Shear Assisted Processing of Materials: Bharat Gwalani1; Matthew Olszta1; Yang He1; Jinhui Tao1; Chongmin Wang1; Tiffany Kaspar1; Aashish Rohatgi1; Peter Sushko1; Arun Devaraj1; 1Pacific Northwest National Laboratory
    Solid phase processing (SPP) of materials uses frictional and shear forces to transforms materials resulting in a noticeable microstructural refinement and nanoscale phases enhancing mechanical properties while fully avoiding melting route. High-speed mass redistribution with concurrent heating of the material, make the atomic-scale mechanisms in such processes quite complex. To understand this process and guide future modifications in SPP techniques we are developed a systematic experimental approach to decouple the effects of shear force, temperature, material properties, and deformation rates, and develop a fundamental atomic-scale understanding of microstructural evolution during processing. We synthesized model binary alloys with well-controlled structural and compositional features. Then we used a tribometer to emulate SPP conditions in small material volumes, thus enabling us to reveal micro-to-atomic length-scale mass transfer. Compositional patterning, forced solutionization, and grain refinement are observed in the immiscible and partially miscible systems.

5:25 PM  
Electrical Conductivity and Wear Properties of Pure Copper Processed by High Pressure Sliding: Evander Ramos1; Takahiro Masuda2; Yoichi Takizawa3; Zenji Horita2; Suveen Mathaudhu1; 1University of California Riverside; 2Kyushu University; 3Nagano Forging Co.
    A variety of severe plastic deformation approaches, such as high-pressure torsion, have been used to apply large strains, and thus engender extreme grain refinement in metallic materials, however scalability has often been limited. In this study, high pressure sliding (HPS), a linear analog of high-pressure torsion, has been utilized to process high purity copper under ambient high-shear, large strain conditions. The influence of this processing on the microstructure, electrical conductivity, and mechanical properties has been explored. These properties are compared to the literature for copper processed by well-established SPD methods to validate the viability of HPS as a scalable SPD process.

5:45 PM  
Simultaneously Reducing Mechanical Anisotropy and Enhancing Ductility in Mg Alloys by Advanced Solid Phase Processing: Dalong Zhang1; Vineet Joshi1; Jens Darsell1; Nicole Overman1; Scott Whalen1; Darrell Herling1; 1Pacific Northwest National Laboratory
     Solid phase processing techniques such as friction stir welding, Shear assisted processing and extrusion (ShAPE)/ friction extrusion and cold spray have been successfully demonstrated as promising thermomechanical methods to produce metallic materials with enhanced performance. In this study, AZ series Mg alloys in the as-received forms, i.e., as-cast or as-extruded, were processed using friction extrusion. Microstructural characterization was performed using EBSD and TEM and revealed that as compared to the feedstock materials/ billets, the friction extruded Mg alloys had more uniform microstructure, equiaxed grains, finer and homogeneously distributed precipitates and chemical homogeneity. It was also observed that the basal planes were not oriented parallel to the extrusion axis. As a result, the rod products exhibited significantly reduced or eliminated the mechanical anisotropy and achieved enhanced ductility, which were uncommon or difficult to attain using conventional processing techniques. In addition, the modified texture likely suppressed deformation twinning under compressive deformation.