Heterostructured and Gradient Materials (HGM V): New Mechanistic Discoveries Enabling Superior Properties: Deformation Mechanisms
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Shaping and Forming Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Yuntian Zhu, City University of Hong Kong; Kei Ameyama, Ritsumeikan University; Irene Beyerlein, University of California, Santa Barbara; Yuri Estrin, Monash University; Huajian Gao, Nanyang Technological University; Ke Lu, Institute of Metal Research; Suveen Mathaudhu, Colorado School of Mines; Xiaolei Wu, State Institute of Mechanics, Chinese Academy of Sciences
Tuesday 2:30 PM
March 21, 2023
Room: Aqua 314
Location: Hilton
Session Chair: Nan Li, Los Alamos National laboratory; Megumi Kawasaki, Oregon State University
2:30 PM Invited
In Situ Pillar Compression to Understand Dislocation-grain Boundary Interactions in Cu: Nan Li1; Dongyue Xie1; Muh-Jang Chen2; Mohammed Zikry2; Darby Luscher1; Abigail Hunter1; Saryu Fensin1; 1Los Alamos National Laboratory; 2North Caroline State University
Grain boundary is one of the most important planar defects in materials. Correlated mechanical response leads to localized strain accumulation and structural evolution. This can determine whether dislocations can nucleate, transmit, or just be blocked at the boundary. In order to understand this process, we have performed in situ pillar compression in a scanning electron microscope coupled with electron backscatter diffraction scanning. The bicrystalline pillars, with the chosen boundary in the middle, are prepared in a shape of rectangular cuboid. Depending on the boundary structure, various interactions with dislocations at the boundary are captured. Correlated with the electron backscatter diffraction mapping at different strain states, we are able to quantify the lattice rotation and local strain tensor along the loading axial. Such information has helped us to better understand the mechanical role of grain boundaries and provided a unique validation for the modeling at both atomic and mesoscales.
3:00 PM Cancelled
Is an Internal Length Gradient (ILG) Extension of Classical Laws Necessary for Understanding Gradient Materials?: Elias Aifantis1; 1Aristotle University of Thessaloniki
A recently advanced framework of Internal Length Gradient (ILG) material mechanics, lead to a robust generalization of classical laws of material physics; in particular, Hooke’s law of elasticity, Fick’s law of diffusion, and von Misses law of plastic flow. A similar extension also applies to the various forms of interatomic/intermolecular potentials used in numerical material behavior simulations. After a brief outline of this methodology, a number of examples for gradient materials are discussed for which conventional models do not suffice to interpret the observed behavior.
3:30 PM
Strain-dependent Phase Transformation Mapping of Diffusion-bonded Nanocrystalline Aluminum-magnesium by High-energy Synchrotron X-rays: Megumi Kawasaki1; Klaus-Dieter Liss2; 1Oregon State University; 2Guangdong Technion – Israel Institute of Technology
Separate metal disks of Al and Mg were mechanically bonded through high-pressure torsion processing for a shear strain of >3,000 under 6.0 GPa compressive pressure. Such high straining through HPT processing synthesized a bulk nanostructured metastable Al alloy with grain sizes of 35-40 nm in a state of supersaturated solid solution with the maximum Mg solubility of ~38.5 at.% via formation of Al-Mg intermetallic phases. This study highlights the capability of high-energy synchrotron X-rays to investigate the polymorphous phase transformation towards the formation of the metastable Al-Mg alloy. The measurements providing diffraction peak profiles at a series of local positions over the sample volume allow mapping of gradual yet significant structural changes in the Al-Mg alloy. The results reveal strain-dependent transformations between f.c.c and h.c.p. phases with a sharp dissolution at strains of ~2500 and subsequent homogenization towards the formation of the metastable Al-Mg alloy.
3:50 PM Invited
Significant Bauschinger Effect and Back Stress Strengthening in an Ultrafine Grained Pure Aluminum Fabricated by Severe Plastic Deformation Process: Nobuhiro Tsuji1; Si Gao1; Kota Yoshino1; Daisuke Terada2; Yoshihisa Kaneko3; 1Kyoto University; 2Chiba Institute of Technology; 3Osaka Metropolitan University
Bauschinger test in uniaxial tension-compression mode was carried out for the first time on the pure Al specimens having homogeneous ultra-fine grained (UFG) microstructures fabricated by equal-channel an- gular pressing (ECAP) and subsequent annealing processes. Significant Bauschinger stress (transient soft- ening), Bauschinger energy parameter and their strong dependences on the tensile plastic pre-strain at the very early stage of the tensile deformation were measured in the UFG specimens, in sharp contrast to their coarse-grained (CG) counterpart. The grain size dependence of the Bauschinger effect in pure Al was qualitatively discussed in terms of the back stress arising from the formation of dislocation pile-up against the grain boundary during plastic deformation.
4:20 PM Break
4:40 PM Invited
Understanding Interfacial Kinetic Processes during Sintering to Enable Heterostructuring: Fadi Abdeljawad1; Omar Hussein1; Keith Coffman2; Eric Lang3; Khalid Hattar3; Shen Dillon4; 1Clemson University; 2University of Illinois; 3Sandia National Laboratories; 4University of California at Irvine
Recent advances in sintering-based manufacturing have enabled the fabrication of hierarchical microstructures with intricate nanoscale features. Examples include nanolattices, nanoporous materials, and stochastic nanostructures. Microstructure here refers to grain and pore size and spatial distributions and pore network topology. In this context, porosity is not treated as an undesired defect, but rather a feature that can be tailored for specific applications. For example, porous microstructures with high surface-to-volume ratio are desired for their electrochemical activity. Herein, we present recent work aimed at understanding interfacial kinetic processes that govern microstructure formation and evolution during nanoscale sintering. Atomistic simulations reveal large variations in sintering rates as a function of grain boundary geometry. Theoretical and computational studies demonstrate the paramount role of local particle packing in coarsening and densification rates and interfacial instabilities during nanoscale sintering. Our work provides much needed process-structure linkages related to the processing of heterostructured materials.
5:10 PM
Strengthening of 3D Printed Cu Micropillar in Cu-Ni Core-shell Structure: Manish Jain1; Amit Sharma2; Patrik Schürch3; Nicolo Maria Della Ventura2; Wabe Koelmans3; Xavier Maeder2; Jakob Schwiedrzik2; Johann Michler2; 1University of New South Wales; 2Empa-Swiss Federal Laboratories for Materials Science and Technology; 3Exaddon AG
In this work, we demonstrate a unique Copper-Nickel (Cu-Ni) core-shell structure for improved strength, while maintaining the shape of 3D printed Cu. An additive micromanufacturing technique based on localized electrodeposition, with a submicron spatial resolution, was utilized to fabricate micropillar-shaped Cu cores. These cores were subsequently coated by pulse reverse electrodeposition with Ni of two different thicknesses: 250nm and 670nm. A combination of in-situ micropillar compression and finite element (FE) simulation demonstrated a remarkable strengthening (~3 times) of the Ni coated Cu micropillar. Transmission Kikuchi diffraction and transmission electron microscopy were utilized to study the microstructure before and after deformation. Data obtained from both experiments and FE simulation were in good agreement suggesting the strengthening depends on the combination of interface characteristics, stress distribution and geometrical effects. The findings of this work can be extended to other material systems and provide a pathway to develop stronger composites for future applications.
5:30 PM
Strengthening Mechanisms in a Heterostructured and Antimicrobial Stainless Steel: Liliana Romero Resendiz1; Yuntian Zhu1; 1City University of Hong Kong
A heterostructured and antimicrobial stainless steel (HS&A SS) consisting of a 316L SS with Cu nanoparticles (NPs) was developed by combining conventional thermo-mechanical techniques. Three different HS microstructures were studied; 1) austenitic ultrafine-grained matrix with homogeneously dispersed Cu NPs (UFG-NP), 2) lamella-like recrystallized austenitic grains surrounded by ultrafine matrix and dispersed Cu NPs (HLS-NP), and 3) lamella-like recrystallized austenitic grains surrounded by ultrafine matrix and ultrafine Cu regions (HLS). An effective contribution of hetero-deformation induced (HDI) strengthening was obtained for all the HS conditions. However, the long-range stress generated by geometrically necessary dislocation pile-ups at the interfaces was higher for the HLS and HLS-NP. The HDI strengthening mechanism had a synergistic effect with the strain-induced phase transformation of austenite to martensite, twinning, high density of grain boundaries, and second phase dispersion. A reduced strength to ductility trade-off of the HS&A SS compared to conventional nanometric and micrometric SS was obtained.