Seeing is Believing -- Understanding Environmental Degradation and Mechanical Response Using Advanced Characterization Techniques: An SMD Symposium in Honor of Ian M. Robertson: Microstructure-Deformation Relationships
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Chemistry and Physics of Materials Committee, TMS: Corrosion and Environmental Effects Committee, TMS: Mechanical Behavior of Materials Committee, TMS: Nuclear Materials Committee
Program Organizers: Kaila Bertsch, Lawrence Livermore National Laboratory; Khalid Hattar, University of Tennessee Knoxville; Josh Kacher, Georgia Institute of Technology; Bai Cui, University of Nebraska Lincoln; Benjamin Eftink, Los Alamos National Laboratory; Stephen House, University of Pittsburgh; May Martin, National Institute Of Standards And Technology; Kelly Nygren, Cornell University; Blythe Clark, Sandia National Laboratories; Shuai Wang, Southern University of Science and Technology
Wednesday 2:00 PM
March 2, 2022
Room: 207C
Location: Anaheim Convention Center
Session Chair: Kaila Bertsch, Lawrence Livermore National Laboratory; Josh Kacher, Georgia Institute of Technology; Stephen House, University of Pittsburgh/ECC; Blythe Clark, Sandia National Laboratory
2:00 PM Invited
The Influence of Microstructural Anisotropy and Strain Rate on the Shear Response of 6061 And 7039 Aluminum Alloys: George Gray1; 1Los Alamos National Laboratory
While the influence of crystallographic texture on metal plasticity has seen in-depth study over the last 40 years, the role of anisotropy (due to either textural or microstructural anisotropy) on shear deformation and fracture remains poorly understood. The development of predictive damage-evolution and fracture models, requires a detailed understanding of the correlated effects between microstructure and anisotropy since many engineered materials possess directional mechanical properties. A recent specimen geometry, the compact forced-simple-shear specimen (CFSS), has been developed and validated as a means to achieve simple shear testing of metals over a range of temperatures and strain rates. The 2-D plane of shear can be directly aligned along specified directional aspects of a material’s microstructure of interest. In this talk, the utility of the CFSS sample geometry to probe crystallographic / morphological anisotropy on the shear-strain response, damage evolution, and failure of various materials is discussed.
2:30 PM Invited
Uncovering the Limits of Grain Boundary Stability through In Situ and In Operando Characterization: Mitra Taheri1; Jaime Marian2; David Srolovitz3; 1Johns Hopkins University; 2University of California, Los Angeles; 3The University of Hong Kong
Grain boundary (GB) stability may be defined as the ability of a GB to continue to absorb point defects without becoming saturated and without changing its macroscopic degrees of freedom (misorientation, inclination), or degrees of freedom. Much debate revolves around local GB stresses and how they evolve with radiation. Through the use of quantitative in situ microscopy, atomic and mesoscale simulations, and machine learning, we explore how GBs evolve as a function of point defect absorption, and specifically, how local stresses evolve throughout the dynamic radiation process. The results have profound implications in developing thermally stable, bulk nanocrystalline materials, and damage tolerant materials.
3:00 PM Invited
In-situ Materials Micromechanics at Extreme Rates above 106 s-1: Christopher Schuh1; 1Massachusetts Institute of Technology
Whereas many in-situ mechanics methodologies are aimed at fine spatial resolution, this talk will review a technique focused on extreme time resolution. With the LIPIT platform (laser induced particle impact test) and a nanosecond camera, we are able to measure velocities of supersonic particles as they strike and rebound from substrates. This provides both quantitative information about energy dissipation during the impact and direct observations of some dissipation mechanisms. When combined with post mortem microscopy, this method reveals new details about mechanisms of deformation and microstructure evolution. And when combined with temperature control and/or low-melting point materials, it offers new opportunities to understand adiabatic temperature rise during deformation at high rates.
3:30 PM Break
3:45 PM Invited
Grain Boundary Diffusion in Stainless Steel from Atomistic Simulations: Diana Farkas1; 1Virginia Polytechnic Institute
Diffusion, particularly chromium diffusion along grain boundaries plays an important role in the corrosion of stainless steels. Austenitic stainless steels can be susceptible to stress corrosion cracking due the breakdown of the protective nature of the surface oxide, affecting crack initiation. Grain boundary diffusion is critically dependent on the details of grain boundary structure and in the present work we utilize atomistic techniques to study this variation. We use empirical potentials and molecular dynamics techniques in a polycrystalline sample with random misorientations. We report a wide variation of grain boundary diffusion coefficients, depending on the specific details of the local grain boundary structure. This can have important implications for the understanding of phenomena such as stress corrosion cracking in these materials.
4:15 PM Invited
On the Evolution of Dislocation Structures in Irradiated Ferritic-Martensitic Steels: G. Robert Odette1; Ben Eftink2; Jack Haley3; David Sprouster4; 1University of California-Santa Barbara
; 2Los Alamos National Laboratory; 3Oxford University; 4Stoneybrook University
Unlike the case of fcc austenitic steels, network dislocation evolution has not been well characterized and modeled in irradiated bcc ferritic martensitic steels. This knowledge gap is very significant, since the evolution of loops and pre-existing dislocation structures affect point defect sink strengths and their biases, as well as the irradiated alloy constitutive properties. TEM shows initially straight screw dislocations evolve into helical configurations, in a simple Fe-Cr binary alloy, due to vacancy bias driven climb. Similar behavior is observed in more complex steels, along with increases in both loop and network dislocation densities. APT studies show dislocations are sites for strong solute segregation and precipitation, including non-equilibrium phases. This talk is divided into three parts: a) an overview the critical need for comprehensive experimental dislocation characterization; b) results from TEM studies; and, c) results from XRD studies, including data from the literature.
4:45 PM Invited
Insight into Deformation of Irradiated Materials through Combined Molecular Dynamics and In-situ TEM Studies: Brian Wirth1; 1University of Tennessee
Molecular dynamics simulations provide the opportunity to 'see'the atomic-scale deformation mechanisms of dislocation - obstacle interactions, albeit usually at accelerated strain rates. By coupling atomic-scale modeling with in-situ straining studies in the transmission electron microscope, significant insight has been obtained that validates key mechanisms predicted in the MD studies. This presentation will highlight studies of dislocation – obstacle interactions performed collaboratively with the Robertson group that led to new insights into the defect-free dislocation channel formation in deformed, irradiated copper and that highlight how fundamental dislocation reaction analysis provided a foundation for the collaborative analysis.
5:15 PM Invited
The Roles of Layering and Interfaces in Radiation Resistance of MAX and MAB Phase Materials: Izabela Szlufarska1; Hongliang Zhang1; Jianqi Xi1; Ranran Su1; Jun Kim1; 1University of Wisconsin-Madison
MAX phase materials are 3D layered ceramics that have shown an unprecedented tolerance to radiation-induced amorphization. However, unfortunately, MAX phases undergo radiation-induced crystalline-to-crystalline phase transformation, which compromises the many advantageous properties of these materials. In this talk, I will discuss how radiation resistance of Ti3SiC2 can be enhanced by engineering multi-layer systems with SiC and TiCx interfaces. I will show that unlike in metals, in ceramics interfaces are not necessarily beneficial to radiation resistance and that it is important to understand details of the defect energy landscape at and near ceramic interfaces. In addition, I will present our findings on radiation resistance of 3D layered borides (MAB phases) relative to MAX phases, I will discuss the role of a 2D Al layer in radiation resistance of the MAB phases, and finally I will introduce design rules we identified for design of MAB phases with enhanced radiation resistance.