Magnesium Technology 2017: Solidification and Processing III and Magnesium-Rare Earth Alloys I
Sponsored by: TMS Light Metals Division, TMS: Magnesium Committee
Program Organizers: Kiran Solanki, Arizona State University; Dmytro Orlov, Lund University; Alok Singh, National Institute for Materials Science; Neale Neelameggham, Ind LLC

Wednesday 2:00 PM
March 1, 2017
Room: 5A
Location: San Diego Convention Ctr

Session Chair: Mark Easton, Royal Melbourne Institute of Technology University; Vineet Joshi, Pacific Northwest National Laboratory

2:00 PM  
Scaled-Up Fabrication of Thin-Walled ZK60 Tubing using Shear Assisted Processing and Extrusion (ShAPE): Scott Whalen1; Vineet Joshi2; David Catalini2; Curt Lavender2; David Field3; 1Pacific Northwest National Laboratory ; 2Pacific Northwest National Laboratory; 3Washington State University
    Shear Assisted Processing and Extrusion (ShAPE) has been used to fabricate ZK60 magnesium tubing having a nominal diameter of 2.0” with wall thicknesses ranging from 0.06” to 0.120”. Application of simultaneous linear and rotational shear at the die face, and between the mandrel and die bearing, during the ShAPE process generates high shear within the flowing material. This combined effect results in significant grain refinement within the extrudate and an order of magnitude reduction in axial force compared to conventional extrusion techniques. An average grain diameter of less than 5 microns through the entire wall thickness and an axial force below 10,000 pounds were achieved. Crystallographic texture is reported showing rotation of the (0001) basal planes away from the longitudinal axis. Die design considerations unique to the ShAPE process such as bearing length, relief angle, and scrolled features are also discussed.

2:20 PM  
Biocompatible Magnesium Alloy ZNdK100 – Adaptation of Extrusion Parameters to Tailor the Mechanical Properties to Different Implant Applications: Rainer Eifler1; Florian Schäfke1; Hans Jürgen Maier1; Christian Klose1; 1Leibniz Universität Hannover
    The magnesium alloy ZNdK100 offers high corrosion resistance and biocompatibility due to low amounts of alloying elements suitable for biomedical applications. Compared with common absorbable magnesium alloys which frequently contain mischmetal, the use of neodymium as a single rare earth element aids in achieving best reproducibility of the degradation behavior while improving the ductility, leading to fracture strains of ~30%. Thus, stents made from this alloy allowed dilatation without failure. The alloy’s strength however turned out to be low (~100MPa). Recent investigations proved that the material’s strength can be significantly increased by an adaptation of the extrusion parameters, such as billet temperature and extrusion ratio, which wield major influence on recrystallization of the microstructure. In the current work, it will be investigated to which extent the mechanical properties can be adjusted through the extrusion process, allowing the use of the same alloy for both bone implants and soft tissue implants.

2:40 PM  
Characterization of Semi-closed Die-forged ZK60 Mg Alloy Extrusion: Seyyedmohamadhasan Karparvarfard1; Sugrib Shaha1; Amir Hadadzadeh1; Hamid Jahed1; Mary Wells1; Bruce Williams2; 1University of Waterloo; 2CanmetMATERIALS, Natural Resources Canada
    The present research aims at characterization of an extruded ZK60 Mg-alloy processed through semi-closed die-forging at the temperature of 450°C with the rate of 0.4mm/s by investigating the compression behavior along the extrusion directions (ED) and radial directions (RD). Microstructural analysis shows a bimodal grain structure in the extruded sample, while the forged samples exhibited grains elongated along the perpendicular direction of forging with no evidence of dynamic recrystallization. It is also seen that the samples in as-extruded condition obtained the ultimate compression strength (UCS) of 449MPa and 335MPa along the ED and RD, respectively. After forging the attained UCS were decreased by ~14% and ~10% for the ED and RD, respectively, while a significant improvement in fracture strain between ~60% and ~92% is observed in the forged samples. It is concluded that the forging is a beneficial technique for significantly improving ductility without sacrificing strength of Mg alloys.

3:00 PM  
Optimization of Nitrogen Bubbling Conditions for Extruded Mg Alloy with Balanced Mechanical Properties: Wonseok Yang1; Youngkyun Kim1; Taeyang Kwak1; Shae K. Kim1; Hyunkyu Lim1; Do Hyang Kim2; 1KITECH; 2Yonsei University
    Although Mg alloys have attracted attention as light-weight structural materials, it has been limited to apply to practical products due to the disproportionate mechanical properties. According to our preliminary test, N2 bubbling have improved the ultimate tensile strength and elongation of extruded Mg-3Al-1Zn-1Ca alloy from 362 MPa and 11.1 % to 374 MPa and 16.5 %. However, the conditions of N2 bubbling are not established yet. In this study, mechanical properties of extruded Mg-3Al-1Zn-1Ca alloys, which were made by various operating temperatures and amounts of N2 gas, were investigated to optimize the conditions of N2 bubbling. The test specimens were prepared by indirect extruder with billets of diameter of 40 mm. The extrusion temperature and ratio were 270 oC and 20, respectively. Also, we discussed the effect of N2 bubbling on Mg melt.

3:20 PM  
Effects of Gadolinium and Neodymium Addition on Young’s Modulus of Magnesium-based Binary Alloys: Yuling Xu1; Jie Li2; Zhengye Zhong1; Karl Kainer1; Norbert Hort1; 1Helmholtz Zentrum Geesthacht; 2Shanghai University
    In order to investigate the influence of solute atoms and particles on Young’s modulus of magnesium, series of binary Mg-Gd and Mg-Nd alloys were prepared using hot extrusion. With increasing Gd content from 0 to 2.654 at.% Young’s modulus of Mg-Gd alloys increases linearly from 44.0 to 45.3 GPa. Regarding Mg-Nd alloys, Young’s modulus firstly decreases to 42.5 GPa until 0.184 at.% Nd, and then increases to 43.4 GPa at Mg-0.628 at.% Nd. The different influences of solutes Gd and Nd on Young’s modulus of Mg are attributed to their different solid solution behaviors in magnesium, which can lead to the alterations of crystal cell parameters and/or different amount of second phases. For Mg-Gd alloys the lattice parameters increase and the axial ratio (c/a) decreases with Gd content increasing. In contrast, for Mg-Nd alloys they almost keep unchanged due to small solubility of Nd in Mg when Nd content increases.

3:40 PM Break

4:00 PM  
Aging Behavior of Mg Alloys Containing Nd and Y: Ellen Solomon1; Timothy Chan1; Andrew Chen1; Benjamin Uttal-Veroff1; Emmanuelle Marquis1; 1University of Michigan
    Magnesium rare earth alloys form unique precipitate structures during aging that make these materials desirable for applications where a high strength to weight ratio is important. Commercial alloys such as WE43 are quite complex, making it difficult to fully understand the factors controlling precipitation in these alloys that are needed in the design of new and improved alloys. In this work, we investigate the evolution of the different precipitate phases that form in Mg-Nd, Mg-Y, and Mg-Nd-Y alloys using scanning transmission electron microscopy and atom probe tomography and relate the microstructure to the measured changes in alloy hardness via post-mortem observations of deformed alloys.

4:20 PM  
Variation of Rare Earth Elements in the Magnesium Alloy ME21 for the Sheet Production: Gerrit Kurz1; Tom Petersen1; Dietmar Letzig1; 1Helmholtz-Zentrum Geesthacht
    This paper reports on the variation of rare earth elements in the aluminum-free magnesium alloy ME21 (2 wt% Mn and 1 wt% RE) in order to investigate the sensitivity to the amount and kind of the rare earth elements regarding strength and ductility. The paper will show the results of casting experiments of some alloy variations of ME21 which contain different amounts of Cerium and Neodymium. The influence of the different alloying elements on the microstructure before and after heat treatment is shown. Furthermore, rolling trials with different schedules are conducted and the mechanical properties of the sheets are presented and discussed with respect to arising textures. The results of this casting and rolling trials are used to discuss how to tailor the mechanical properties of the magnesium alloy ME21.

4:40 PM  
Phase Stability and Formation in Mg–Gd–Zn Alloys – Key Data for ICME of Mg Alloys: Rainer Schmid-Fetzer1; Joachim Gröbner1; Suming Zhu2; Jian-Feng Nie3; Mark Gibson4; 1Clausthal University of Technology; 2RMIT University; 3Monash University; 4CSIRO
    Thermodynamic databases of multicomponent alloy systems are the indispensable basis to apply and develop ICME of Mg alloys. Among the multicomponent Mg alloys with rare earths (RE) and Zn the Mg-Gd-Zn system is found to be a prime example of complex phase formation, both under stable and metastable conditions. This alloy system was studied by a combination of dedicated experiments and thermodynamic modeling. Two metastable phases, I and H2, have been identified in as-cast Mg-rich Mg–Gd–Zn alloys by TEM characterization. Quantitative thermodynamic descriptions of metastable Mg–Gd–Zn phases and metastable phase diagrams are developed, embedded in a complete Calphad modeling of all stable phases. Dedicated thermodynamic calculations using constrained Scheil solidification simulation reveal conditions for I and H2 phase formation and transformation.