Heterostructured and Gradient Materials (HGM IV): Tailoring Heterogeneity for Superior Properties: Poster Session
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
Tuesday 5:30 PM
March 16, 2021
Room: RM 40
Location: TMS2021 Virtual
Effect of Layer Spacing and Elastic-plastic Mismatch on Fracture Toughness of Ti-TiN Multilayers: Ashwini Mishra1; Hariprasad Gopalan2; Marcus Hans3; Christoph Kirchlechner4; Jochen Schneider3; Gerhard Dehm2; Nagamani Balila1; 1Indian Institute of Technology Bombay; 2Max-Planck-Institut für Eisenforschung GmbH; 3RWTH Aachen University; 4Karlsruhe Institute of Technology
TiN is a hard protective coating that suffers from extreme brittleness. The present study explores if multilayering it with an elastically and plastically soft Ti layer can help improve its damage tolerance. Ti-TiN multilayers with different layer spacings and volume fractions are modeled using finite element simulations to derive their stress intensity factor solutions since a homogeneous assumption does not hold true. They are subsequently deposited by physical vapor deposition and their fracture behavior studied through micro-cantilever fracture tests. These values are compared to monolithic TiN. It is seen that multilayers with finer layer spacing lead to high fracture toughness. This phenomenon can be explained based on the stress distributions in individual layers. A secondary aspect of test geometry in achieving stable crack growth in multilayers is also discussed as a means of studying its R-curve behavior.
Evolution of Diffusion Joint of Al-steel Clad Strip during Heat Treatment: Barbora Krivska1; Michaela Šlapáková1; Rostislav Králík1; Lucia Bajtošová1; Miroslav Cieslar1; Mykhailo Stolbchenko2; Olexandr Grydin2; Mirko Schaper2; 1Charles University; 2Paderborn University
Aluminum-steel clad composite is a material of great potential for various industrial applications due to a combination of a low density of Al and a high strength of steel. A high corrosion resistance and a low cost of both monomaterials makes the clad strip even more attractive. A suitable option of a flat composite preparation is twin-roll casting, which is supposed to be an energy and material saving method. Additionally, a subsequent heat treatment could be applied to enhance the diffusion joint. However, using high-temperatures procedures is limited by a formation of a brittle intermetallic layer in the interfacial region between steel and aluminum, which essentially influences the final mechanical properties of the composite. In the study, effect of subsequent annealing was investigated. Experimental methods including electron microscopy and resistometrical measurements were complemented by finite element method calculations for further interpretation of the measured data.
Hierarchical Morphologies in Co-sputter Deposited Immiscible Alloy Thin Films: Max Powers1; 1University of Michigan
Co-sputtered immiscible alloys form a number of interesting morphologies depending on the processing conditions. Recent research of co-deposited Cu-Mo and Cu-Ta thin films have revealed a novel morphology consisting of hiearchical structures which mean there are distinct features present at different length scales in the film. To determine the underlying thermodynamics and kinetics that lead to this unique morphology a series of immiscible alloy pairings were studied: Cu-Mo, Cu-Ta, Cu-Ag, Cu-Fe, Mo-Ag, and Cu-Mo-Ag. Experimentation revealed the presence of hierarchical structure is tied to the disparate kinetics of the depositing constituent elements at elevated deposition temperatures. With disparate kinetics, the element with a melting temperature comparable to the processing temperature will diffuse large distances and agglomerate, trapping the immobile element as nano-precipitates. Adjacent, macroscopic phase separation for immiscible systems occurs. In the case of constituent elements with similar kinetics, e.g. Cu-Fe, Cu-Ag, the resultant microstructure only contains macroscopic features.
Origin of Enhanced Ductility in Laser Rapid Solidified Heterogeneous Hypereutectic Al-20Si Alloy: Slip Interactions between Soft Al Matrix and Hard Si Fibers?: Huai-Hsun Lien1; 1University of Michigan
Micropillar compression revealed enhanced flow strength for laser rapid solidified (LSR) heterogeneous Al-20Si as compared to as-cast Al-12Si. This strength increase can be attributed to the refined Si fiber with diameter averaging 50 nm and reduced interfiber spacing with similar length scale. In addition, much higher degree of uniform deformation was observed for LSR alloy. Postmortem SEM and TEM suggested co-deformability between Al matrix and Si fibers, which dislocations was observed in both phases. Several length scales exist within the LRS Al-Si alloy: the μ m-size primary Al dendrites, which is embedded in nm-size Al-Si ultrafine eutectic, and nanotwins within the Si fibers. in-situ SEM and in-situ TEM further reveal the deformation behavior and slip mechanisms for LRS microstructures. These findings are crucial to understanding the interactions between nanoscale hard soft phases and to constructing the microstructure to mechanical property map for tailoring the mechanical properties.
Work Hardening of Gradient FeCrAl Alloy: An In- situ Micropillar Compression Study: Tianyi Sun1; Zhongxia Shang2; Jaehun Cho2; Jie Ding2; Yifan Zhang2; Tongjun Niu2; Bo Yang2; Dongyue Xie3; Jian Wang3; Haiyan Wang2; Xinghang Zhang2; 1Purdue University; 2Purdue University, School of Materials Engineering; 3University of Nebraska-Lincoln
FeCrAl alloy is a promising cladding material for next generation nuclear reactor as it has excellent high temperature oxidation resistance necessary for accident scenarios. In this study, a model FeCrAl alloy, C35M, was processed by surface mechanical grinding treatment. Microscopy studies show the formation of gradient microstructures, and the outermost layer contains nanolaminates with less than 100 nm in thickness. In situ micropillar compression studies were performed at various treated regions and showed the treated FeCrAl alloy has good work hardening ability. Furthermore, the work hardening ability appears to be grain size dependent. A modified Kocks-Mecking model was utilized to explain the grain size-dependent work hardening behavior. This study sheds lights on the design of gradient steels with high-strength and good work hardening ability for future nuclear reactor applications.