Heterostructured and Gradient Materials (HGM IV): Tailoring Heterogeneity for Superior Properties: Heterostructured Materials I: Fundamentals
Sponsored by: TMS Structural Materials Division, 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; Yves Brechet, Grenoble Institute of Technology; Huajian Gao, Nanyang Technological University; Hyoung Seop Kim, Pohang University of Science and Technology; Ke Lu, Institute of Metal Research; Xiaolei Wu, State Institute of Mechanics, Chinese Academy of Sciences
Monday 8:30 AM
March 15, 2021
Room: RM 46
Location: TMS2021 Virtual
Session Chair: Cem Tasan, Massachusetts Institute of Technology; Jongun Moon, POSTECH; Yujie Wei, Institute of Mechanics, CAS; Deliang Zhang, Northeast University
8:30 AM Invited
Gradients, Singularities and Interatomic Potentials: K. Parisis1; Elias Aifantis1; 1Aristotle University of Thessaloniki
First a review is given on gradient theory which has been shown to eliminate singularities from dislocation lines and crack tips, provide thickness and spacing of shear bands and modeling hardening vs. softening behavior. Then its applicability to derive enhanced interatomic potentials is illustrated.References [1] E.C. Aifantis, A Concise Review of Gradient Models in Mechanics and Physics, Front. Phys. 7, 239 (2020).[2] E.C. Aifantis, Gradient Extension of Classical Material Models From Nuclear & Condensed Matter Scales to Earth & Cosmological Scales, arXiv:1909.08616 (2020). [3] E.C. Aifantis, Internal length gradient (ILG) material mechanics across scales and disciplines, Adv. Appl. Mech. 49, 1–110 (2016).
8:55 AM Invited
Microstructure Dependence of Strain Partitioning and Localization in Heterostructured Metals: C. Tasan1; 1Massachusetts Institute of Technology
Plastic deformation is an intrinsically heterogeneous process that proceeds through iterative strain localization and delocalization processes at the micro-scale. The extent of the strain localization, however, depends on the microstructural characteristics. For example, in multi-phase alloys, strong partitioning of the strain is typically observed that governs the microscopic strain patterns that develop. Recently, development of novel in-situ scanning electron microscope deformation methods has enabled access to a realm of information regarding both microstructure and micro-strain evolution, in a coupled manner. Over the last decade, we have employed these methods to test steels, titanium alloys, high entropy alloys, and others, exploring the factors that govern strain partitioning and localization in heterostructured metals. In this talk, these results will be discussed, to provide an overview of these key factors. A further discussion point will be regarding the opportunities such data enable towards alloy and microstructure design.
9:20 AM Invited
Nanoscale Heterogeneity and Gradients Engineered by Compositional Defect Decoration and Manipulation: The Atomic Scale Basis of Segregation Engineering: Dierk Raabe1; 1Max-Planck Institute
Defects can be chemically manipulated by solute decoration through partitioning between defect and matrix at equal chemical potential. Such Gibbsian equilibrium segregation effects do not only lead to strong confined partitioning but also to low-dimensional transformations, altering the defects’ energy, mobility, structure, and cohesion. Some of these phenomena have been described already long ago: Examples are Cottrell atmospheres at dislocations, Suzuki partitioning to stacking faults and grain boundary segregation according to the adsorption isotherm. However most of these models only consider interaction-free partitioning, with the implicit assumption that the decorated defects behave like low-dimensional solid solutions. The lecture shows that real segregation phenomena are thermodynamically far more complex, characterized by substantial interaction among the segregating species, leading to a wide variety of low-dimensional phase-like states.
9:45 AM Invited
Cu-Fe Based Immiscible Medium-entropy Alloys with Excellent Tensile Properties: Jongun Moon1; Jeong Min Park1; Jae Wung Bae1; Peter Liaw2; Hyoung Seop Kim1; 1POSTECH; 2The University of Tennessee
In the present work, Cu-Fe based immiscible medium-entropy alloys with excellent mechanical properties are proposed. Alx(CuFeMn)100-x (x = 0, 7.5, and 15 atomic percent, at.%) alloys were developed by utilizing the immiscible nature of Cu-Fe alloys. The phase separation into Cu-rich and Fe-rich dual domains induces microstructural and compositional heterogeneities to the alloys, and the addition of Al transforms the crystal structure from dual face-centered-cubic to face-centered-cubic and L21 structures. The alloys exhibit high strengths because of hetero-deformation-induced strengthening caused by heterogeneous microstructures. The presence of nano-scale twins also enhances the strength of the alloys. In particular, the twinning-mediated martensitic phase transformation from L21 to 18R-type martensite phases plays a significant role in strengthening the alloys at cryogenic temperatures.
10:10 AM Invited
Thickness-dependent Shear Localization in Cu/Nb Metallic Nanolayered Composites: Caizhi Zhou1; Shujing Dong1; 1University of South Carolina
Metallic nanolayered composites (MNCs) are a special class of composite materials made from alternative layers of different constituents with the layer thickness at nanometer scale. Recent studies have shown clear length scale-dependent plastic deformation instability in MNCs, as the shear band formed in samples with layer thickness below a critical value. In this work, we performed molecular dynamics simulations to study the effect of layer thickness on the shear localization in Cu/Nb MNCs. Our simulation results achieve good agreement with experimental results that the inverse size effect in the strength occurs in samples with layer thickness below 2.0 nm. The strain softening observed in those samples was triggered by the shear localization. The quantitative analysis revealed that the unsymmetrical dislocation transmission across the interface induces the shear localization and promotes the shear band formation in Cu/Nb MNCs. The plastic strain mainly comes from the interface sliding within the shear band.
10:30 AM
Heterostructured Materials: An Emerging Materials Field with Great Potential: Yuntian Zhu1; Xiaolei Wu2; Chongxiang Huang3; 1North Carolina State University; 2Institute of Mechanics, CAS; 3Sichuan University
Strong and tough materials are desired for light-weight applications such as electric cars and aerospace applications. Recently, heterostructures are found to produce unprecedented strength and ductility that are considered impossible from our textbook knowledge and materials history [1]. Heterostructured materials consist of heterogeneous zones with dramatic (>100%) variations in mechanical and/or physical properties. The interaction in these hetero-zones produces a synergistic effect where the integrated property exceeds the prediction by the rule-of-mixtures [2]. Importantly, HS materials can be produced by current industrial facilities at large scale and low cost. There are many scientific issues with such materials that challenge the communities of experimental materials science and computational material mechanics. Heterostructured materials is quickly becoming a hot research field in the post-nanomaterials era. In this talk I’ll present the current advances as well as future challenges and issues in this emerging field.