12th International Conference on Magnesium Alloys and their Applications (Mg 2021): Applications
Program Organizers: Alan Luo, Ohio State University; Mihriban Pekguleryuz, McGill University; Sean Agnew, University of Virginia; John Allison, University of Michigan; Karl Kainer; Eric Nyberg, Kaiser Aluminum Trentwood; Warren Poole, University of British Columbia; Kumar Sadayappan, CanmetMATERIALS; Bruce Williams, Canmetmaterials Natural Resources Canada; Stephen Yue, Mcgill University
Tuesday 8:00 AM
June 15, 2021
Room: Plenary
Location: Virtual
Session Chair: Alan Luo, Ohio State University
8:00 AM Plenary
Advances in Magnesium Alloys for Automotive Applications: Anil Sachdev1; 1General Motors Company
Innovations in the aluminum and steel industries are providing significant challenges to widespread application of magnesium components in automotive applications. Key barriers are mechanical properties including strength and ductility and corrosion mitigation. Alloying with rare earth elements can improve mechanical properties but adds cost. This talk will demonstrate how multi-scale computational methods, including a recently funded program by the Department of Energy, are addressing the challenge of reducing cost and improving properties to make magnesium alloys competitive for high volume applications in the automotive industry. The talk will address the needs and challenges and provide examples of alloy development for sheet, castings and extrusions. A key driver is the need to reduce or eliminate the dependency on expensive rare-earth alloying additions without compromising properties. The discussion on sheet material will additionally include the need for warm stamping and judicious choice of lubrication, corrosion coatings, and joining techniques for large vehicle body components. Finally, the talk will touch upon advanced materials models and their validation to predict material composition and processing conditions for optimum use of magnesium for specific applications.
8:30 AM Plenary
Development and Applications of High Plasticity Magnesium Alloys: Fusheng Pan1; 1Chongqing University
It is well known that Mg has a typical close packed hexagonal structure with few movable slip systems. Compared with aluminum alloys and steels, low plasticity and poor formability of magnesium alloys seriously restricts their wide application. How to improve the plasticity without damaging strength or vice versa has become a research hotspot and focus for development of new types of magnesium alloys in the world. In the past decade, Chongqing University and other units have done a lot of work in the development of high plasticity magnesium alloy, and proposed an alloy design theory of "solid solution strengthening and plasticizing (SSSD)". It is found that the solid solution of some specific atoms in magnesium can not only improve the strength by hindering the slip of basal plane dislocation, but also improve the plasticity by narrowing the slip resistance gap between the basal plane and the non-basal plane and thus promote the activation of non-basal slip. As a result, both strength and plasticity of the magnesium alloy are improved simultaneously. The development of SSSD theory provided a new way to balance and optimize the strength and plasticity of magnesium alloys in the past ten years. Based on this theory, Chongqing University has developed a variety of new high plasticity magnesium alloys, of which more than 10 alloys have been listed in the National Standard or International Standard. The elongation of ultra-high plasticity magnesium alloy can reach to over 65%, and the elongation of ultra-high strength wrought magnesium alloy with σ b > 500MPa can reach to more than 10%.
9:00 AM Plenary
Characterization and Continuum Modeling of a Rare-earth Magnesium Alloy Leading to Full-scale Auto Parts: Michael Worswick1; Tim Skszek2; Srihari Kurikuri3; Cliff Butcher1; Armin Abedini1; Mariuzs Boba1; Kaab Omer1; 1University of Waterloo; 2Magna International Inc.; 3National Research Council of Canada
This presentation provides an overview of material characterization and model development studies performed on a texture-modified rare earth magnesium alloy sheet (ZEK100). Wrought magnesium alloys are attractive for automotive industry applications due to their low density and high specific strength. However, commercial magnesium alloys, such as AZ31B sheet usually have poor formability at room temperature due to limited activity of slip systems. Additionally, due to the twinning deformation mechanism activated in specific loading directions, magnesium alloys exhibit an asymmetric stress-strain response in uniaxial tension and compression tests. The formability of magnesium alloys can be improved by deforming at elevated temperatures; however, warm forming of AZ31B requires a more complex heated tooling setup which increases the cost of the forming operation. Alternatively, the formability can be improved by the addition of rare-earth elements such as Ce, Nd, Y and Gd, for example, which have been shown to weaken the basal texture. Constitutive, formability and fracture characterization of both AZ31B and ZEK100 sheet is presented, considering both room and elevated temperature conditions over a wide range of strain rate. The mechanical behavior can be related back to the initial crystallographic texture in light of known deformation mechanisms operating at different orientations and strain rates. Extensive tensile and compressive constitutive characterization experiments were performed on both alloys, including characterization of anisotropy with strain and material strain rate- and temperature-sensitivity. Forming limit characterization was also performed at elevated temperatures using in situ digital image correlation (DIC) strain measurement. The ZEK100 alloy exhibits significantly higher formability at temperatures below 250°C, whereas the two alloys have similar formability in the 250-300°C range. Yield criteria capturing the evolving anisotropy and asymmetry of magnesium sheet alloys are proposed to model the complex behavior of magnesium alloys at room and elevated temperatures. At room temperature, the material behavior of both alloys is highly anisotropic and asymmetric; however, the degree of asymmetry and anisotropy is diminished at elevated temperature. The proposed material model is validated against several laboratory-scale experiments: 3-point bending, limiting dome height (LDH) and limiting draw ratio (LDR) experiments. Full-scale forming trials are performed considering prototype door inner and roof outer tooling. AZ31B and ZEK100 blanks were formed with initial elevated temperatures, but with room temperature tooling. The AZ31B blanks failed during forming whereas the ZEK100 blanks were successfully drawn for temperatures above 250°C. Recent constitutive models suitable for warm forming conditions using commercial forming software (Autoform) and are shown to provide predictions in accord with the forming trials.