Characterization of Minerals, Metals and Materials 2021: Characterization of Mechanical Properties
Sponsored by: TMS Extraction and Processing Division, TMS: Materials Characterization Committee
Program Organizers: Jian Li, CanmetMATERIALS; Mingming Zhang, Baowu Ouyeel Co. Ltd; Bowen Li, Michigan Technological University; Sergio Monteiro, Instituto Militar de Engenharia; Shadia Ikhmayies; Yunus Kalay, Middle East Technical University; Jiann-Yang Hwang, Michigan Technological University; Juan Escobedo-Diaz, University of New South Wales; John Carpenter, Los Alamos National Laboratory; Andrew Brown, Devcom Arl Army Research Office; Rajiv Soman, Eurofins EAG Materials Science LLC; Alex Moser, Naval Research Laboratory

Wednesday 8:30 AM
March 17, 2021
Room: RM 15
Location: TMS2021 Virtual

Session Chair: Bowen Li, Michigan Technological University; Shadia Ikhmayies, Al Isra University


8:30 AM  
Effect of Specimen Dimension on Plasticity Behaviour Below Submillimetre Scale: Arijit Lodh1; Gustavo Castelluccio1; 1Cranfield University
     The mechanical response of metallic materials results from a complex hierarchy of deformation mechanisms across scales. Certainly, recent approaches aimed at predicting these responses of metals have innovated with the formulation and characterization of multiscale strengthening mechanisms. One of such mechanism originates on grains or sample boundaries, which limit the dislocation glide paths and results in the so-called Hall-Petch strengthening effect. However, limited experimental work has quantified the strengthening role for samples with cross sections between 50 μm to 500 μm.In this presentation we first introduce a novel approach to manufacture and test sub-millimetre tensile samples. Various sized metallic samples were prepared using precision micro-milling to examine specimen size effect. The samples were deformed under monotonic deformation till fracture. For polycrystalline copper, the results present a dependence of the yield response on the sample dimension, which is analogous to that observed for different grain sizes.

8:50 AM  
Significant Disparity of Non-basal Dislocation Activities in Hot-rolled Mg and AZ31 Alloy Under Tension: Dexin Zhao1; Xiaolong Ma1; Abhinav Srivastavaa1; Griffin Turner1; Ibrahim Karaman1; Kelvin Xie1; 1Texas A&M University
    AZ31 alloy exhibits much better tensile ductility than pure Mg. However, the underpinning mechanisms remain unexplored at dislocation level. In this work, we deformed hot-rolled pure Mg and AZ31 samples with similar microstructures under tension along rolling direction. We then investigated their deformation mechanisms using transmission electron microscopy. Systematic tilting experiments and statistical analyses at different strain levels revealed a significant disparity of non-basal dislocation activities between them. For pure Mg, <c + a> dislocations were activated since the early stage of plastic deformation. The <c + a> dislocations display much shorter dissociation distance compared to the ones reported from c-axis compression. For AZ31, <c + a> dislocations were largely absent at all strain levels, even in the strain-to-failure samples. The absence of <c + a> dislocations and the presence of profuse non-basal <a> dislocations could be the key to elucidate the much-improved ductility in AZ31 compared to pure Mg.

9:10 AM  
Analysis of Wear Issues in the Rotary Shear Biomass Comminution System: Kyungjun Lee1; Lianshan Lin2; Dave Lanning3; Ercan Cakmak2; James R. Keiser2; Jun Qu2; 111612 Lanesborough Way; 2ORNL; 3Forest concepts
    To understand wear of rotary shear comminution system used for size-reduction of biomass, comprehensive studies of worn components and the extrinsic inorganic particles (EIPs) have been conducted. First, EIPs that came with the biomass during harvesting were characterized. Each component was investigated in terms of the degree of wear, geometry, and mechanical properties according to their materials: 304 SS for spacers, Copper alloy 770 for clearing plates, and A2 tool steel for cutters. Based on the results, the correlation between EIPs and worn components and the wear mechanism were revealed. EIPs caused severe wear of tools, which reduced processing efficiency within a short time. Finally, selected candidate materials and surface treatments were evaluated and compared to the cutter material currently in use. The research was sponsored by the Feedstock Conversion Interface Consortium (FCIC) of the Bioenergy Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE).

9:30 AM  
Characterization of Solidification Structure Morphology in High-carbon Steel Billet by Fractal Dimension: Jianghai Cao1; Zibing Hou1; Zhiqiang Peng1; Dongwei Guo1; Ping Tang1; 1Chongqing University
    High-carbon steel is one of the typical high-end steels, and its solidification morphology have great influence on the quality of steels. In this work, fractal dimension was introduced to describe solidification structure morphology in 82B cord steel billet with 0.82 wt% carbon content. Fractal dimension was calculated using box-counting method (DBox), sandbox method (DSand) and branching method (DBran). It was demonstrated that the fractal dimension is effective to characterize quantitatively the complexity of solidification structure morphology. The value of fractal dimension calculated by the above three methods are not the same due to different calculation methods describe solidification structure characteristics from different angles. In additional, the relationship between fractal dimension and secondary dendrite arm spacing (SDAS) and segregation area ratio (Rseg) was discussed. Fractal dimension calculated by box-counting method was well-correlated with SDAS and Rseg. This result demonstrated box-counting method can better reflect solidification characteristics of the billet than sandbox method and branching method.

9:50 AM  
Dislocation Creep at Low Stresses and High Temperature: Harper-Dorn Creep Revisited: Shobhit Singh1; Michael Kassner2; Praveen Kumar1; 1Indian Institute of Science, Bangalore; 2University of Southern California
    The present investigation deals with the deformation mechanism involved in the high temperature-low stress creep (also known as the Harper-Dorn creep) in ionic crystals (LiF and NaCl) and Al single crystal. After long term annealing at high temperature, a frustration dislocation density is observed in these crystals. This frustration density restricts any further refinement of network density. Hence, a stress independent dislocation density is observed in Harper-Dorn creep. However, crystals initially grown with quite low dislocation density, which is below this frustration limit, can show a stress dependence at such low stresses. The observed creep exponent can be observed to be between 1 and 3 in the Harper-Dorn creep regime based on the initial dislocation density. A model which is based on the higher dependence of dislocation climb velocity on the applied stress is presented to explain the creep exponents observed in Harper-Dorn as well as ‘five’ power-law creep.

10:10 AM  
The Study of Structure-mechanical Properties Relationship in Different Cross-linked SU-8 Thermoset Polymers: Prakash Sarkar1; Prita Pant1; Hemant Nanavati1; 1Indian Institute of Technology Bombay
    SU-8 is a cross-linked thermoset amorphous polymer, which is involved to design micro-electrical mechanical system (MEMs) components. We are interested to measure elastic modulus (Er) and hardness (H) of different cross-linked SU-8. To study this, we have fabricated samples by following standard photolithography process. The amount of cross-linking is estimated by Fourier-transform infrared spectroscopy (FTIR). Nanoindentation experiments are performed to measure Er and H values at 800μN maximum load. By following conventional method, high Er and H values are obtained for less cross-linked samples and vice-versa. The main reasons are adhesion between the tip surface and contact sample surface, viscoelasticity and wrong measurement of contact area (Ac). After minimization of adhesion effect and viscoelasticity, we have considered Ac as residual area obtained from scanning probe microscopy (SPM). Thereafter, for less (~82%) and high (~95%) cross-linked samples, obtained Er is 4.61±0.13GPa and 5.02±0.18GPa, and H is 256.97±1.42MPa and 285.48±1.17MPa respectively.