Heterostructured and Gradient Materials (HGM V): New Mechanistic Discoveries Enabling Superior Properties: Gradient and Nano-twinned Materials
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
Wednesday 8:30 AM
March 22, 2023
Room: Aqua 314
Location: Hilton
Session Chair: Darcy Hughes, Sandia National Laboratories; Gianna Valentino, John Hopkins Applied Physics Lab
8:30 AM Invited
Gradient Bulk Nanostructures with Exceptional Strength via High Load Sliding: Darcy Hughes1; 1Sandia National Labs (ret.)
Plowing of tailored wedge shaped micro-asperities along the surface of Cu induces steep gradients with increasing subsurface depth that include size scales from 3.5 nm to 150,000 nm with a high hardness of 3.4 GPa at the finest scale. substructural gradients are measured with transmission electron microscopy. Microprobe and STEM show that the nanoscale structure is stabilized by Fe.Subsurface stresses are calculated based on the measured structural parameters in a linear addition of the Hall-Petch formulation for the inverse spacing of geometrically necessary boundaries, 〖1/D〗avGNB, plus Taylor dislocation hardening, ρavIDB . A further unification of these parameters is made since the density ρavIDB is directly proportional to〖1/D〗avGNB. A quantitative energy balance between the friction and deformation energies corroborate the high hardness for application to hard components and metal processing.
9:00 AM
Defect-interface Interactions and Nanomechanical Behavior of 3D interfaces in Ti/Nb Nanolaminates: Mauricio De Leo1; Justin Cheng1; Shuozhi Xu2; Jon Baldwin3; Irene Beyerlein4; Nathan Mara1; 1University of Minnesota; 2University of Oklahoma; 3Los Alamos National Lab; 4University of California, Santa Barbara
Chemically sharp interfaces in nanolayered composites or “2D interfaces”, enhance mechanical properties such as strength and hardness, yet their ductility and toughness limit applications. Widening these heterophase interfaces chemically and crystallographically provides a region of crystallographic transition, or “3D interfaces”, increasing the ductility and toughness of the material by attenuating the transmission of dislocation pileups. Here, we introduce 3D interfaces to DC magnetron sputtered hcp/bcc Ti/Nb nanolayered composites to enhance their mechanical behavior. 3D interface layer thicknesses (h’) introduced range from 5 to 40 nm on composites with pure layer sizes (h) from 5 to 40 nm respectively. Corresponding 2D interface composites were studied as well. We report Berkovich nanoindentation, micropillar compression, and transmission electron microscopy results to visualize the structure-property relationships leading to mechanical enhancement due to 3D interfaces, and discuss our findings in the context of atomic-level modeling of dislocation-interface interactions including dislocation transmission, blocking and storage.
9:20 AM
Influence of Strain Gradients in Heterostructured Nanomaterials: Daniel Goodelman1; Andrea Hodge1; 1University of Southern California
Heterostructured nanomaterials are a promising solution for optimizing strength-ductility synergy, due to hard and soft domains that deform at different rates. Recently, we developed heterostructured Inconel 725 films with complex microstructures after heat treatment. Features including abnormally large grains, nanocrystalline and nanotwinned regions, as well as delta phase, rafted structures, and precipitates were observed. The strain gradient in the film appears to drive the mechanisms that lead to such complex microstructures, although these effects are not yet fully understood. In this work, nanotwinned Inconel 725 films were synthesized using magnetron sputtering, where variations in the deposition conditions contribute to differences in the stress and strain states of the film. Extensive characterization before and after heat treatment is performed to evaluate the microstructural complexity for various stress and strain values. Mechanical behavior is examined in both the as-sputtered and heat treated state to understand the deformation mechanisms correlated to the microstructure.
9:40 AM Invited
Ultrahigh Strength and Strain Localizations in Nanotwinned Ni-Mo-W Alloys: Gianna Valentino1; 1Johns Hopkins Applied Physics Laboratory
The engineering of mechanical properties and performance of materials has traditionally relied on the exploitation of the processing-structure-property relations as a design tool to synthesize new materials. Nanostructured materials are no exception and have received considerable attention in recent years for thin film protective coatings, microelectromechanical systems, and many other engineering applications aimed to achieve a balance of strength and ductility. Sputter-deposited Ni-Mo-W films have been shown to possess ultrahigh strength, highly anisotropic plasticity, low electrical resistivity, and low thermal expansion that stem from finely spaced growth twins (<5 nm). Here we report on in-situ SEM micropillar compression and post-mortem microstructural analysis to elucidate the fundamental deformation mechanisms that underpin the extreme strength and plasticity in nanotwinned Ni-Mo-W. Emphasis will be placed on the loading orientation with respect to the coherent twin boundaries and local strains, both of which are key to uncovering the mechanisms underpinning the unique deformation behavior.