Progress towards Understanding the Synthesis and Behavior of Metals Far from Equilibrium: A SMD Symposium Honoring Enrique Lavernia on the Occasion of His 60th Birthday: Nanostructured Metals III
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Composite Materials Committee
Program Organizers: Haiming Wen, Missouri University of Science and Technology; Suveen Mathaudhu, Colorado School of Mines; Yuntian Zhu, City University of Hong Kong; Manoj Gupta, National University of Singapore; Kaka Ma, Colorado State University; Troy Topping, California State University Sacramento; Yizhang Zhou, University of California, Irvine; Joshua Yee, Sandia National Laboratories; Dalong Zhang, Pacific Northwest National Laboratory; Yaojun Lin, Wuhan University of Technology; Fei Chen, Wuhan University of Technology
Tuesday 8:30 AM
February 25, 2020
Room: 31B
Location: San Diego Convention Ctr
Session Chair: Timothy Rupert, University of California – Irvine; Jessica Krogstad, University of Illinois, Urbana-Champaign
8:30 AM Invited
Controlling Grain Boundaries (GBs) in Processing and Properties: From Computing GB Diagrams to Understanding Embrittlement and Stabilizing Nanoalloys: Jian Luo1; 1University of California, San Diego
Grain boundaries (GBs) can be considered as 2-D interfacial phases that are also called “complexions” to differentiate them from bulk Gibbs phases. In this talk, I will first review a series of our studies to compute GB “phase” (complexion) diagrams via interfacial thermodynamic models [see, e.g., APL 92:101901 (2008), Current Opinion 2:81 (2008) & 20:268 (2016), PRB 84:014105 (2011), JACerS 95:2358 (2012), Acta 91:202 (2015) & 130:329 (2017), and Scripta 130:165 (2017)], hybrid molecular dynamics (MD) and Monte Carlo (MC) atomistic simulations [PRL 120:085702 (2018) and Scripta 158:11 (2019)]] and (most recently) machine learning. Second, recent observations of GB complexions in two classical GB embrittlement systems, Ni-Bi [Science 333:1730 (2011) & 358:97 (2017)] and Ni-S [Nature Comm. 9:2764 (2018)], will also be discussed. Third, I will discuss our recent studies to successfully stabilize nanocrystalline alloys at high temperatures (>1000 C) via utilizing high-entropy GBs [Scripta 124:160 (2016) and beyond].
9:00 AM Invited
High-strength and Thermal Stability of Nanotwinned Al Alloys: Qiang Li1; Sichuang Xue1; Yifan Zhang1; Jian Wang2; Haiyan Wang1; Xinghang Zhang1; 1Purdue University; 2University of Nebraska, Lincoln
Lightweight Al alloys show widespread applications, but are subjected to limitations, such as inherently low strength and low service temperature. Age hardened Al alloys have mechanical strength less than ~ 700 MPa and readily experience grain growth at low homologous temperature. We have used far-from-equilibrium approach to fabricate various Al solid solution alloys. Some of the selected Al alloys have flow stresses exceeding 1.5 GPa, making them one of the strongest Al alloys. Our in situ studies show that the nanotwinned Al alloys possess obvious anisotropy under both tension and compression tests in SEM microscope. The solid solution Al alloys have superb thermal stability and mechanical stability at elevated temperatures. These studies shed light on the design of lightweight high strength Al alloys in harsh environment.
9:30 AM
Review of Thermal Stability of Nanocrystalline and Nanostructured Materials and Methods how to Control it: Lilia Kurmanaeva1; 1INT, KIT (Germany); MSE, University of California, Davis (USA)
Downsizing is still one of the main trends in the research for a commercial application, and nanostructured (NS) metal and alloys are a possible solution to obtain the desired properties in small size and volume. However, usually, there is a strong dependence of the advanced properties upon the grain size. The far from equilibrium nanocrystalline structures contain a high fraction of grain boundaries, which makes the system thermodynamically unstable, especially in a single component NS metals; and the slight temperature increase could often lead to rapid grain growth and be detrimental for the required properties. There are several approaches for the structure stabilization and the suppression of the grain boundary migration. The recent work will present an overview of methods on how to maintain advanced properties and to stabilize the structure, for example by the retardation of boundary migration by the action of solutes and second-phase particles.
9:50 AM
Thermal Stability of Nanostructured Ferritic and Austenitic Stainless Steels: Maalavan Arivu1; Andrew Hoffman1; Jiaqi Duan1; Haiming Wen1; 1Missouri University of Science and Technology
Nanostructured steels have recently gained attention due to the roles of grain boundaries (GBs) in enhancing mechanical strength and absorbing irradiation induced defects. In order to produce bulk nanostructured steels, severe plastic deformation (SPD) techniques such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT) have been developed as effective grain refinement techniques. One concern for nanostructured materials, however, is their thermal stability as the stored strain energy and GB energy can act as driving forces for recrystallization and grain growth. In this study, ECAP and HPT processed Kanthal-D (FeCrAl, ferritic) and 304SS (FeCrNi, austenitic) were annealed at temperatures ranging from 500-700 oC. Microhardness was used to determine temperatures at which these steels become thermally unstable. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to determine microstructures after annealing. In both ECAP processed steels recrystallization occurs, while the HPT processed steels show grain growth.
10:10 AM Break
10:30 AM Invited
Novel Microstructures from Non-equilibrium Processing of Metal Powder: Kenong Xia1; 1University of Melbourne
Materials in the form of powder have been used by nature and humans since ancient times. The relatively young metal powder has been playing an increasingly important role in such advanced fields as nanotechnology and additive manufacturing. In conventional powder metallurgy, metal particles are sintered at high temperatures for long times, destroying any non-equilibrium microstructures that might be desirable. We have used emerging technologies based on severe plastic deformation (SPD) and selective laser melting (SLM), respectively, to produce far-from-equilibrium metals consisting of sophisticated combinations of phases and microstructures. Examples of novel alloys processed by SPD consolidation and SLM of powder will be presented, including Al-C and Al-Al2O3 nanocomposites, hierarchy-structured dual-phase Al/Ti and hybrid titanium alloys. The hybridisation of microstructures, in particular, leads to properties significantly superior to those of the ingredient alloys, heralding a new strategy for future alloys.
11:00 AM Cancelled
Microstructures and Tensile Mechanical Properties of Ultrafine Grained Al and Cu Matrix Nanocomposites Fabricated by High Energy Mechanical Milling and Thermomechanical Powder Consolidation: Deliang Zhang1; Lei Cao2; Wei Zeng2; Wenjing Wang2; Jiamiao Liang2; Enrique Lavernia3; 1Northeastern University; 2Shanghai Jiao Tong University; 3University of California, Irvine
High energy mechanical milling of Al or Cu powder together with stearic acid powder (as process control agent) and other metal powders such as Nb powder leads to formation of nanocrystalline Al or Cu matrix nanocomposite powders. Thermomechanical consolidation of these powders by spark plasma sintering and hot extrusion produces bulk ultrafine grained Al or Cu matrix nanocomposites reinforced with Al3C4/Al2O3, C and NbC nanoparticles. The enhancement of atomic bonding of interparticle boundaries and presence of coarse grains in the microstructure facilitated by processing or heat treatment can effectively improve the tensile ductility of the material, leading to excellent combinations of relatively high strength and high tensile ductility. This talk will present the major findings of our work in this area and discuss correlations between microstructure and mechanical properties of the materials fabricated.
11:30 AM
Electrodeposition of Nanostructured Nickel Foils: Alan Jankowski1; 1Sandia National Laboratories
There are many synthesis methods through phase space to produce nanostructures in metals. Condensation methods with rapid solidification are extensively explored from the gas or liquid phase. In particular, electrodeposition using pulsed currents favors continuous nucleation in the processing of structures to produce free-standing sheets as well as protective coatings for surfaces. An analysis approach used to develop the method for refining the structure and surface finish for nanocrystalline gold-copper alloy coatings relates the energy in each deposition pulse to the constituent grain size that forms during growth. Application is now pursued to predetermine the grain size of nanocrystalline nickel foils formed by pulsed electrodeposition. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
11:50 AM
Severe Plastic Deformation Enhanced Segregation and Precipitation in Nanostructured Steels: Andrew Hoffman1; Maalavan Arivu1; Haiming Wen1; 1Missouri University of Science and Technology
During severe plastic deformation (SPD) processing, materials are subjected to high strains and often moderate to high temperatures. SPD therefore creates a state far from equilibrium, which can affect the stability of the system significantly. In this study, austenitic 304L and Kanthal-D Fe-Cr-Al stainless steels were both subjected to SPD using high pressure torsion (HPT) and equal channel angular pressing (ECAP). Samples were studied using various electron microscopy techniques as well as atom probe tomography (APT). APT results on the 304L steel showed that after HPT at 300°C Ni, Mn, and Si segregated towards grain boundaries, causing the formation of Ni-Mn-Si precipitates. After both ECAP at 500°C and HPT at 300°C Kanthal-D was found to contain a large number density of Cr enriched M23C6 carbides, which was associated with Cr and C segregation towards and Al depletion at grain boundaries.