Magnesium Technology 2020: Keynote Session
Sponsored by: TMS Light Metals Division, TMS: Magnesium Committee
Program Organizers: J. Brian Jordon, Baylor University; Victoria Miller, University of Florida; Vineet Joshi, Pacific Northwest National Laboratory; Neale Neelameggham, IND LLC

Monday 8:00 AM
February 24, 2020
Room: 6C
Location: San Diego Convention Ctr

Session Chair: J. Brian Jordon, University of Alabama; Victoria Miller, University of Florida


8:00 AM Introductory Comments

8:10 AM  Keynote
Twin Transmission Across Grain Boundaries in Mg: Carlos Tome1; M Arul Kumar1; John Graham1; Khanh Dang1; Yue Liu2; Pengzhang Tang2; Shujuan Wang1; Rodney McCabe1; Laurent Capolungo1; 1Los Alamos National Laboratory; 2Shanghai Jiao Tong University
    Transmission of {1012}<1011> mechanical twins across grain boundaries in Mg is a mechanism that can facilitate intergranular crack propagation by providing a path to cracks along along the twin interface. Until now the focus has been on a 2D characterization of twin transmission along the forward propagation direction. Recent 3D studies of the twin domain interface reveal anisotropic mobility and a relative easiness of lateral twin propagation as opposed to forward or normal propagation. Here we study the forward and the lateral twin transmission into neighbors applying a variety of experimental and computational characterization techniques, namely: (1) statistical EBSD analysis of twin sections; (2) Phase Field simulations of twin growth; (3) 3D Molecular Dynamic simulations of twins reacting with grain boundaries. This study improves our understanding of the transmission mechanisms in a 3D aggregate, and helps us to develop criteria for treating twin modeling in CP simulations.

8:55 AM  Keynote
Hierarchically Structured Ultrafine Grained Magnesium Alloys: Rajiv Mishra1; 1University of North Texas
    The intrinsic low density of magnesium drives research towards high performance magnesium alloys. Hierarchically structured ultrafine grained magnesium alloys possess exceptional strength-ductility combination and eliminate many of the traditional drawbacks like low strength, high yield strength asymmetry, poor formability and limited superplasticity. In this overview presentation, friction stir processed microstructures are used as examples to discuss the microstructural paradigms that can exhibit excellent balance of mechanical properties. These show the possibilities of exceeding 500 MPa strength with good work hardening and >10% ductility. Use of micron-sized boron carbide (B4C) and nano-sized yttria (Y2O3) powder can simultaneously enhance modulus-strength-ductility combination. High strength ultrafine grained magnesium alloys also show high strain rate superplasticity which can provide pathways for overcoming poor formability. An example of friction stir additive manufacturing will be used to discuss possibilities of implementing such microstructures at component level with emerging solid-state additive manufacturing techniques.

9:40 AM Break

10:00 AM  Keynote
MultiStage Fatigue (MSF) Modeling of Magnesium in a Corrosion Environment: Mark Horstemeyer1; 1Liberty University
    This work presents an overview of using the MultiStage Fatigue model with a corrosion model to capture the behavior of magnesium alloys. One can argue that magnesium alloys used for structural components are always in a corrosive environment as no real practical structural component operates in a vacuum. As such, different magnesium alloys are analyzed in the context of their fatigue incubation, Microstructurally Small Crack (MSC), and long crack regimes under a vacuum, air, and salt-water environments. The different magnesium alloys analyzed including: AE44, AM30, AM50, AM60, AZ31, AZ61, AZ91 alloys. These alloys were fabricated under different methods and each had different heat treatments. The levels of corrosion pitting, general corrosion, and filiform corrosion were quite different for each alloy, meaning that the interdependence of the different corrosion mechanisms interacted differently with each alloy’s incubation, MSC, and LC fatigue lives. These points will be delineated and explained in this presentation.

10:45 AM  Keynote
Novel Texture Controlling of Mg Alloys: Bin Jiang1; Guangsheng Huang1; Fusheng Pan1; 1Chongqing University
    Conventionally extruded Mg alloy sheets possess poor mechanical properties due to the strong basal texture. This brings about a poor deformation capability of sheet thinning and a stronger anisotropy and consequently results in limited number of available plastic deformation modes. In this work, a novel extrusion approach to get high strength magnesium alloy plates will be introduced. A suitable constitutive model of differential speed extrusion is established to ameliorate the texture-dependent mechanical properties. The yield stress of AZ31 alloy sheet has been increased from 161.2 MPa to 179.9 MPa and the elongation has been improved from 15.4 % to 20.1 %. AZ61 alloy sheets’ ultimate tensile strength was increased from 387.9 MPa to 427.1 MPa and the yield stress was improved from 147.7 MPa to 195.9 MPa. Grain refinement and tilted weak basal texture obtained by differential speed extrusion process.