Heterostructured and Gradient Materials (HGM IV): Tailoring Heterogeneity for Superior Properties: Heterostructured Materials II: Mechanical Properties
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 2:00 PM
March 15, 2021
Room: RM 46
Location: TMS2021 Virtual
Session Chair: Mingxin Huang, The University of Hong Kong; Ruslan Valiev, Ufa Aviation Technical University; Xiaolong Ma, Pacific Northwest National Lab.
2:00 PM Invited
Grain-boundary Delamination-induced Toughening in 2 GPa Deformed and Partitioned Steel: Li Liu1; MingXin Huang1; 1University of Hong Kong
The present work demonstrates that exceptional damage-tolerance can be achieved in an ultra-strong deformed and partitioned (D&P) steel with a yield strength of ~2GPa. We demonstrate that increasing the yield strength is not detrimental to the toughness, but instead it can facilitate the activation of a delamination toughening mechanism. Specifically, the ultrahigh yield strength enables a secondary fracture mode, delamination cracking, at interfaces normal to the primary fracture surface. Delamination toughening associated with intensive but controlled cracking at Mn-enriched prior-austenite grain boundaries normal to the primary fracture surface provides an extra energy release rate for fracture as well as enhancing crack-tip blunting, collectively elevating the overall fracture toughness. Such delamination toughening combined with transformation-induced plasticity (TRIP) toughening are rarely realized simutaneously in structural materals. The combination enables an intringuing combination of strengh, ductility and toughness properties in the D&P steel.
2:25 PM
Enhanced Mechanical Properties in 3D Interface Metallic Multilayers: Justin Cheng1; Jon Baldwin2; Nan Li2; Shuozhi Xu3; Irene Beyerlein3; Nathan Mara1; 1University of Minnesota Twin Cities; 2Los Alamos National Laboratory; 3University of California, Santa Barbara
The role of nanoscale interfacial gradients in enhancing mechanical properties is a topic that is not been fully explored. Here we introduce nanoscale chemical and structural inhomogeneities in 3 dimensions at heterophase interfaces in Cu/Nb nanolaminates to form 3D interfaces. These materials are ideal for studying defect-gradient interface interactions due to their high interfacial content and ability to consistently vapor deposit materials with known chemistry and microstructure. We have found that the introduction of nanoscale 3D interfaces strengthens Cu/Nb in micropillar compression perpendicular to the interfaces without sacrificing deformability. We investigate the origins of this phenomenon by performing micropillar compression tests in isostrain, isostress, and 45° tilted loading conditions. These conditions quantify the barriers facing interfacial shear and shear transfer across interfaces, allowing us to explain how shear localization is mediated by defects in 3D interface Cu/Nb under different loading conditions.
2:45 PM
Enhanced Mechanical Properties of Interface-strengthened UFG Tungsten and Tungsten-based Nanocomposites: Michael Wurmshuber1; Simon Doppermann1; Markus Alfreider1; Michael Burtscher1; Daniel Kiener1; 1Montanuniversitaet Leoben
Ultra-fine grained and nanocrystalline materials are making a strong case for deployment in high-performance applications, due to the interesting material properties arising from the large amount of interfaces within the material. However, these interfaces also play an important role in fracture processes in such materials, as they can provide a relative easy path for crack propagation. In order to improve the fracture performance of ultra-fine grained and nanostructured materials, doping with interface-cohesion enhancing elements is performed in this work. Ultra-fine grained tungsten was chosen as a model material, due to its inherent brittleness and its exciting possible application in nuclear fusion facilities. After this proof of concept, nanocrystalline W-Cu composites, combining the advantages of a hard and a soft phase, were fabricated with and without doped interfaces. A series of micromechanical in-situ experiments was performed to investigate the effect of the interface doping on strength, ductility and fracture toughness.
3:05 PM
Effect of Alloying Additions on the Strength of Confined Nanocrystalline Layers: Sevda Fathipour1; Amir Motallebzadeh2; Özgür Duygulu3; Sezer Ozerinc1; 1Middle East Technical University; 2Koç University; 3TÜBİTAK Marmara Research Center
Nanolayered metals are nanostructured materials composed of alternating metals with submicron layer thickness. Their outstanding mechanical properties and thermal stability have been the subject of many studies in the last two decades. Almost all of these studies have focused on nanolayers composed of pure metals. On the other hand, little is known about the effect of alloying additions on the mechanical behavior of metallic nanolayers. In this work, we prepared magnetron sputtered films of Cu-Cu50Nb50 and Cu90Nb10-Cu50Nb50 nanolayers with layer thicknesses in the range of 10 – 100 nm. The size-independent nature of the Cu50Nb50 amorphous layers enabled us to focus on the effect of alloying additions in the crystalline layers. The results show that alloying additions to Cu considerably enhances the hardness of the nanolayered composite. Similar to the behavior of pure-metal nanolayers, the strength of alloyed nanolayers increases with decreasing layer thickness.
3:25 PM Invited
Heterostructured Ultrafine-grained Metallic Materials with Enhanced Superplasticity and Superior Strength: Ruslan Valiev1; Maxim Murashkin1; Nguyen Chinh2; 1UFA State Aviation Technical University; 2Eötvös Loránd University
Herein, the possibility of ultrafine-grained (UFG) materials to demonstrate superplasticity at unusually low temperatures maintaining its high-strength state is reported for the first time. The UFG structure with the segregation of alloying elements at grain boundaries has been formed a number of commercial Al alloys by using severe plastic deformation (SPD) techniques. The obtained heterostructured UFG alloys exhibited good thermostability when testing or annealing up to 170 °C. Deforming by tensile test at a strain rate of 10-4 s-1 and 10-3 s-1, the elongation to failure at 120 and 170 °C exceeds 250% and 500%, respectively, whereas the strain rate sensitivity reaches 0.45, which is a typical value characterizing superplastic deformation. After superplastic deformation, the UFG alloy maintains up to 50% higher strength characteristics at RT than that after conventional heat treatment T6. The origin of such superior behavior of the UFG alloys resulting from GB segregations is discussed.
3:50 PM Invited
Hierarchical 3D Nanolayered Duplex-phase Zr with High Strength, Strain Hardening, and Ductility: Weizhong Han1; 1Xi'an Jiaotong University
Nanolayered, bimetallic composites are receiving increased attention due to an exceptional combination of strength and thermal stability not possible from their coarse-layered counterparts or constituents alone. Yet, due to their 2D planar, unidirectional arrangement, they are highly anisotropic, which results in limited strain hardening and ductility. Here we present the formation of a novel hierarchical microstructure, comprised of crystals consisting of 3D nanolayered alpha/beta-Zr networks. By direct comparison with coarse-layered material of the same chemistry, we show that the unusual hierarchical 3D structure gives rise to high strain hardening, high strength and high ductility. We discovered that the 3D randomly oriented bi-phase boundaries result in progressively dispersive rather than localized slip with increasing strain. Dislocation activity in the alpha-Zr lamellae transitions from single slip to multi-slip and eventually to multi-modal slip as strain increases. Ref. PRL-2019-255501 and MRL-2020-8-307.