Magnesium Technology 2020: Alloy Development
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 2:30 PM
February 24, 2020
Room: 6C
Location: San Diego Convention Ctr
Session Chair: Norbert Hort, MagIC - Helmholtz Zentrum Geesthacht; Neale Neelameggham, IND LLC
2:30 PM Invited
Design of Ductile Rare-earth-free Magnesium Alloys: William Curtin1; Rasool Ahmada1; Binglun Yin1; Zhaoxuan Wu2; 1Institute of Mechanical Engineering, École Polytechnique Fédérale de Lausanne; 2Institute of High Performance Computing
Pure Mg has low ductility due to a transition of <c+a> pyramidal dislocations to a sessile basal-oriented structure [1]. Dilute alloying generally improves ductility. Enhancement of pyramidal cross-slip from the lower-energy Pyr. II plane to the higher energy Pyr. I plane has been proposed as the mechanism [2]. Here, the theory is applied to ternary and quarternary alloys of Zn, Al, Li, Ca, Mn, Sn, K, Zr, and Sr at dilute concentrations, and a wide range of compositions are predicted to have good ductility [3]. Interestingly, while Zn alone is insufficient for achieving ductility, its inclusion in multicomponent alloys at 0.5at% enables ductility at the lowest concentrations of other alloying elements. Further implications of the theory are discussed. [1] Z. Wu, W.A. Curtin, Nature 526 (2015) 62-67 [2] Z. Wu et al., Science 359 (2018) 447-452[4] R. Ahmad et al., Acta Materialia 172 (2019) 161-184
3:00 PM
Microstructure Evolution and Precipitation Strengthening in Ca-containing Mg-rare Earth Alloys: Qianying Shi1; Bruce Williams2; John Allison1; 1University of Michigan; 2CanmetMATERIALS, Natural Resources Canada
The significant precipitation strengthening during aging provides Mg-rare earth (RE) alloys exceptional strength. The low density and reasonable cost of Ca could favor Mg alloys for commercial use with improved properties. Our goal is to investigate the potential interaction effect of Ca for improving the aging response and strength of Mg-RE alloys. In this study, 0.5wt.% and 1.0wt.% Ca were added to the ternary alloy Mg-2wt.%Nd-4wt.%Y. The microstructures of different conditions were characterized by DSC, SEM, EPMA, TEM and APT techniques. The microstructure evolution and phase transformations were also determined by commercial CALPHAD software. Vickers hardness tests were performed to compare aging response of different alloys. Current results showed that 0.5wt.%Ca addition is able to accelerate peak aging. The results from this study lay the groundwork for the strength prediction in a quaternary Mg-alloy system using a multi-scale optimization framework which is currently under development within the PRISMS Center.
3:20 PM
A Die-cast Magnesium Alloy for Applications at Elevated Temperatures: Xixi Dong1; Eric Nyberg2; Shouxun Ji1; 1Brunel University London; 2Tungsten Parts Wyoming
The application of magnesium alloys in internal combustion engines has advantages of lightweight, better damping and noise reduction and less vibration during operation. The lightweight benefits can be amplified up to 10 times for pistons application based on the theoretical and experimental confirmations. However, the applications of magnesium pistons in internal combustion engines are still difficult due to the demanding work environment and the rigorous requirements of the increased mechanical performance, thermal conductivity and corrosion resistance at elevated temperatures. The development of high temperature die-cast magnesium alloys for piston applications is therefore challenging, as the high temperature mechanical performance, the die-casting capability and the thermal conductivity usually conflict with each other. Here we report a die-cast magnesium alloy for the piston applications at elevated temperatures, and the alloy development and the piston manufacturing process are introduced.
3:40 PM
Effect of Gd and Nd Additions on the Thermo-mechanical Response of a MgMn Alloy: Domonkos Tolnai1; Serge Gavras1; Pere Barriobero-Vila2; Andreas Stark1; Norbert Schell1; 1Helmholtz-Zentrum Geesthacht; 2DLR
Alloying Mg with Mn improves the strength and the corrosion resistance. The addition of rare earth elements weakens the texture and improves the age hardening response. Nd and Gd are ideal elements to investigate the effect of low and high solid soluble rare earth in Mg on the thermo-mechanical behavior of MgMn. For this purpose a Mg alloy with 1wt.% Mn was modified with an addition of 1wt.% Gd, 1wt.% Nd and with their combination, respectively. In situ synchrotron radiation diffraction was performed during solidification and compression to analyse the solidification sequence of the phases and the deformation behavior of the material. The compression experiments have been performed at room temperature and 350°C up to a deformation of 0.3 with a deformation rate of 10-3 s-1. The compressed samples were subsequently subjected to electron backscattered diffraction to investigate the post mortem microstructure.
4:00 PM
Development of Ultra Lightweight, Corrosion Resistant Mg Alloys: Taylor Cain1; Joseph Labukas1; 1US Army Research Laboratory
The development of Mg-Li alloys to create ultra lightweight alloys has become popular in recent years and presents intrinsic interest from both a technologic and academic perspective. While most studies have focused on either α-HCP or duplex α+β Mg-Li alloys, little work has been performed on the development of BCC β-Li alloys which are stable at concentrations greater than approximately 10.3 wt% Li. This research explores the evolution of microstructure on the hardening response and corrosion resistance of BCC Mg-Li alloys using traditional Mg alloying elements in combination with cathodic poisons. Early results have shown that Ge is effective in improving the corrosion resistance and passivity of binary β-Li but offers little benefit to improving hardening response. The synergistic effect of tertiary and quaternary additions with Ge on mechanical behavior and corrosion resistance is currently under investigation and will be presented on.
4:20 PM Break
4:40 PM Poster Pitches