Magnesium Technology 2017: Poster Session
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

Tuesday 6:00 PM
February 28, 2017
Room: Hall B1
Location: San Diego Convention Ctr

Session Chair: Dmytro Orlov, Lund University

I-23: A High-specific-strength and Corrosion-resistant Magnesium Alloy: Wanqiang Xu1; Michael Ferry1; 1University of New South Wales
    Ultra-lightweight alloys with high strength, ductility and corrosion resistance are desirable for applications in the automotive, aerospace, defence, biomedical, sporting and electronic goods sectors. Ductility and corrosion resistance are generally inversely correlated with strength, making it di°cult to optimize all three simultaneously. Here we design an ultralow density (1.4 g cm−3) Mg–Li-based alloy that is strong, ductile, and more corrosion resistant than Mg-based alloys reported so far. The alloy is Li-rich and a solute nanostructure within a body-centred cubic matrix is achieved by a series of extrusion, heat-treatment and rolling processes. Corrosion resistance from the environment is believed to occur by a uniform lithium carbonate film in which surface coverage is much greater than in traditional hexagonal close-packed Mg-based alloys, explaining the superior corrosion resistance of the alloy.

I-24: A Study on the Mechanical Characteristic of Heat Dissipation Magnesium Alloy by Thixomolding Process: Ho Seung Jang1; Jong Moon Park1; Sueng Hoon Yang1; No Jin Park1; Min Su Park2; Myung Hoon Oh1; 1Kumoh National Institute of Technology/Materials Science and Engineering; 2Jangwontech Co. Ltd.
    Magnesium alloy is a metal having the highest specific strength utility of metal. It has excellent dimensional stability and machinability. The demand for weight reduction and improved fuel economy grows for the main cause of global warming, such as auto parts and aircraft components has been used as a core material. In this study, the mechanical properties were evaluated by using magnesium alloy composition thixomolding process. This process is made by slurry to form a mixture of liquid and solid, and excellent an array of microstructures and low porosity and deformation strength is excellent. It is possible to fine molding. It’s similar to the injection molding of plastics and is called thixomolding. It were used the magnesium alloys(AZ91D, AM50, AM60 etc.) in the experiment. Barrel temperature in the thixomolding process(93.49%) can be seen as having a dominant effect on the tensileˇyield strength, elongation and hardness.

I-25: Characterization of Ultrafine Grained WE43 Magnesium Alloy by Equal-channel Angular Pressing and High Pressure Torsion Process: Camila De Souza1; Tung Nguyen1; Marc Meyers1; Bingfeng Wang2; 1University of California, San Diego; 2Central South University, P.R. China
    Industry applications always fueled the needs of searching for superior materials which would satisfy the manufacturing criteria and improve the quality of final products. For these important reasons, the study of WE43 Magnesium alloy was proposed due to its low density compared with those of copper and aluminum alloys. Even though, this Magnesium alloy satisfied the most vital condition, low density, it still demonstrated some drawbacks of its mechanical behaviors such as hardness and toughness. However, its mechanical behaviors were modified by severe plastic deformation (SPD) technique that was carried out using ECAP and HPT procedures under controlled temperature and loading. The grain size of Magnesium alloy was reduced under high pressure as well as elevated temperature. When the grain size decreased, its mechanical behaviors were improved.

I-26: Constrained Groove Pressing of AZ31 and ZE10 Magnesium Alloys: Mariia Zimina1; Jan Bohlen2; Dietmar Letzig2; Gerrit Kurz2; Michaela Šlapáková1; Jan Bajer1; Miroslav Cieslar1; 1Charles University in Prague; 2Helmholtz-Zentrum Geesthacht
    Constrained groove pressing (CGP) is a severe plastic deformation technique which was successfully applied to aluminium alloys production. Its proved efficiency can be also employed for magnesium alloys. In this study AZ31 and ZE10 magnesium alloy sheets produced using twin-roll casting (TRC) were subjected to CGP. Evolution of the microstructure, texture and mechanical properties was studied using light optical and scanning electron microscopy as well as microhardness and tensile testing. Results show that the combination of TRC and CGP results in improvement of materials properties. The effect of the alloys composition on the mechanical behavior was also studied. Due to the presence of rare-earth elements it is possible to stint recrystallization in ZE10 alloy, thus, a finer grain structure is achieved. Crucial features of the brand new class of sheet structural alloys with high solid solution supersaturation imposed by TRC and ultra-fine grained structure after CGP are distinguished.

I-27: Damage and Fracture in Magnesium AZ31, Experiments and Modeling: Babak Kondori1; Ahmed Benzerga1; 1Texas A&M University
    The microscopic damage mechanisms operating in a hot-rolled AZ31B are investigated under uniaxial and controlled triaxial loadings. The fracture locus exhibits a maximum at moderate triaxiality and the strain-to-failure is found to be greater in notched specimens than in initially smooth ones. A micromechanics-based continuum damage model with a Gurson-like void growth yield criterion for porous materials and a fully analytical shape-dependent void/crack coalescence part is used to rationalize the main findings. Based on image analysis data from broken specimens, only the second phase particles are considered as void nucleation sites in notched bars. Using only one fitting parameter, the predicted fracture strains qualitatively capture the experimental trends. The analysis suggests that the ductile fracture of magnesium alloy AZ31 involves limited void opening/blunting and is controlled by void coalescence. The results provide the groundwork for understanding the effects of microstructural and loading variables on damage and fracture in Mg alloys.

I-28: Development of High Strength Mg Alloys with Good Formability at Room Temperature: T.T.T. Trang1; J. Zhang2; A. Zargaran1; J.H. Kim1; J.H. Hwang1; Nack J. Kim1; 1Graduate Institute of Ferrous Technology (GIFT) and CAAM, Pohang University of Science and Technology (POSTECH); 2Harbin Engineering University
    Being the lightest materials with high specific strength, magnesium alloys have shown their potential to compete with other alloys (steels, Al, etc.) for automotive applications. Nevertheless, applications of magnesium alloys remain limited due to their poor formability at room temperature. This is attributed to the strong basal texture and the limited number of active slip systems in magnesium alloys. Our current research aims to weaken the basal texture yet to enhance the strength at the same time by applying new alloy design concept. Developed alloy exhibits a relatively good tensile properties (YS: ~212 MPa, UTS: ~307 MPa and total elongation of ~17 %), but the stretch formability at room temperature is found to be significantly improved, giving the Index Erichsen (IE) value of 8 mm, which has not been achieved at such a high strength level. The role of alloying additions in microstructural evolution and mechanical properties will be discussed.

I-29: Effects of Alloying Elements on Mechanical and Corrosion Properties of Extruded Mg-Al-Ca Alloys: Hyunkyu Lim1; Wonseok Yang1; Tae yang Kwak1; Youngkyun Kim1; Young-Ok Yoon1; Shae K. Kim1; 1KITECH
    Although magnesium alloys have attracted attention as light-weight structural materials due to the low density, their low absolute strengths and low ignition-resistance should be improved to apply to aerospace and military industries. Therefore, the most researches on the development of magnesium alloys have been focused to find the solutions for these drawbacks. However, up to now many researches have been concentrated on improving only one property which is the strength or the ignition-resistance. So, it should be needed study on the enhancement of multi-properties. According to our preliminary test, N2 bubbling have improved mechanical properties of extruded Mg-3Al-1Zn-1Ca alloy. In this study, effects of Al or RE addition on mechanical and corrosion properties of extruded Mg-Al-Ca alloys with N2 bubbling process were investigated. 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.

I-30: Enhancement of Impact Fracture Toughness of Magnesium Alloys by Microstructure Modification: Toshiji Mukai1; Takayuki Hase1; Naoko Ikeo1; Masatake Yamaguchi2; 1Kobe University; 2Japan Atomic Energy Agency
    Understanding fracture behavior under impact loading is important to be used as structure materials in vehicles. In this research, fracture behavior of magnesium alloys bearing calcium, zinc and aluminum was examined by impact three-point bending test to clarify the microstructural factor affecting crack propagation. As a result, the crack propagation rates in the Mg-Ca-Zn and Mg-Ca-Al alloys were found to be lower than that in commercially available pure magnesium, and absorption energy was enhanced in the ternary alloys. On the other hand, effect of solute segregation on grain boundary strength was estimated by the first-principles calculation. The grain boundary cohesive energy was computed from rigid-type tensile test calculation performed on (11-21) boundary cell model of pure magnesium, the binary and ternary alloys. Direct comparison of the cohesive energy revealed that zinc and calcium solute atoms enhance the grain boundary strength in tension.

I-31: First-principles Model of Alloy-dependent Magnesium Corrosion: Krista Limmer1; Joseph Labukas1; Michael Garvey2; Santanu Chaudhuri2; Jan Andzelm1; 1U.S. Army Research Laboratory; 2University of Illinois Urbana-Champaign
    The rapid corrosion of magnesium is one of the primary limitations for using magnesium in lightweight structural applications. Recent experimental work has suggested that As poisons the cathodic reaction on magnesium, preventing hydrogen recombination and evolution. In this study the mechanism of cathodic poisoning from metalloid alloying was investigated from first principles using density functional theory. The effect of metalloids was investigated by examining the cathodic reaction on multiple surface configurations within the alloy system including: 1) dilute metalloid concentrations in magnesium solid solution, 2) second phase precipitates, and 3) metalloid adatoms. The effect on corrosion was determined by considering the kinetic barriers associated with hydrogen diffusion, recombination, and evolution. This mechanistic understanding of how metalloids contribute to the poisoning of magnesium corrosion may be used to develop magnesium alloy systems with reduced corrosion kinetics.

I-32: First Principles Modeling of <c+a> Dislocations in an Mg-Y Alloys: Daniel Buey1; Maryam Ghazisaeidi1; 1Ohio State University
    Room temperature ductility of magnesium can be improved significantly through alloying with yttrium. The addition of the solute improves ductility by activating non-basal slip modes, namely dislocations with a <c+a> burger’s vectors. Using atomistic modeling, we examine the behavior of edge <c+a> dislocations in magnesium with the addition of yttrium solutes at various points around the dislocation, and use a solute strengthening model to determine the effect these additions have on the strength of the material. We show that the shape of the dislocation core and the separation of the partial dislocations change with the addition of solute atoms. Next we determine the change in strength of the material based on the interaction energy between each solute atom position and the dislocation. The interaction energies close to the core are determined using density function theory (DFT), while the interaction energies outside of the immediate core are approximated with linear elasticity.

I-33: Formability Analysis on Optimized Condition of Superplastic Forming of Magnesium Alloy Sheet: Gopal Kumaresan1; K Kalaichelvan2; 1Production Technology, MIT Campus, Anna University; 2Ceramic Technology, Anna University
    Superplastic sheet metal forming allows the production of complex parts that are not formable under normal conditions. Superplastic sheet metal forming processes are normally based on the same common principle: the sheet metal is firmly clamped between the die halves and is blow-formed by means of gas pressure. Generally superplastic forming can only be achieved in a very narrow range of strain rates and temperature. Superplastic materials are relatively stable when deformed; this behavior is related to the observation that the flow stress of a superplastic material is very sensitive to the rate of deformation. This paper aims to study the formability characteristic of Magnesium alloy by considering variable parameters, such as the sheet thickness, forming pressure and forming temperature. The forming time of 120 minutes is constant for all samples.

I-34: Hot Blank – Cold Die (HB-CD) Stamping of Magnesium Alloy Sheets _ Material Characterization and Modeling: Fadi Abu-Farha1; Abdelrahim Lhal1; Zeren Xu1; Nan Zhang1; 1Clemson University
    Hot blank – cold die (HB-CD) stamping offers great opportunities for high production rate and low cost forming, while overcoming the limited formability issues with certain lightweight alloy sheets, particularly magnesium, when compared to isothermal warm and hot forming operations. This work investigates the HB-CD stamping potentials of magnesium alloy sheets for automotive applications. Detailed mechanical testing, aided by digital image correlation (DIC), was carried out over a wide range of temperatures and strain rates to fully characterize the flow behavior of two magnesium alloys (AZ31B and ZEK100). Microstructural examination was also carried out to correlate the differences in texture and grainstructure to the mechanical behavior of both alloys. Constitutive models, taking the different deformation mechanisms the materials undergo during HB-CD into account, were developed and fitted using the experimental data. A customized hot-stamping simulator setup for controlled non-isothermal tensile testing was developed and used for model calibration.

I-35: Hydrogen Uptake by Magnesium Alloys during Aqueous Corrosion: Michael Brady1; Anton Ievlev1; Mostafa Fayek2; Donovan Leonard1; Harry Meyer III1; Matthew Frith1; Luke Daemen1; Anibal Ramirez-Cuesta1; Olga Ovchinnikova1; Lawrence Anovitz1; Gernot Rother1; Dongwon Shin1; Guang-Ling Song3; Bruce Davis4; 1Oak Ridge National Laboratory; 2University of Manitoba; 3Xiamen University; 4Magnesium Elektron North America
    We have observed significant penetration of deuterium (D) beyond the surface film and into the underlying metal for Mg alloys exposed in water at room temperature using D2O and Secondary Ion Mass Spectrometry (SIMS) isotopic tracer techniques. This penetration was enhanced by minor (< 1 wt.%) alloying additions of Zr and Nd in both model cast and wrought alloys. Pure Mg and AZ31B (Mg-3Al-1Zn base) exhibited far less preferential D penetration, while cast AZ91 with 8 wt.% Al exhibited higher levels. Cross-section imaging by TOF-SIMS confirmed the penetration of D into the underlying metal, and further suggested preferential D segregation associated with second phases and/or grain boundary structures. This presentation will overview these findings, as well as the in-progress investigation into the speciation of hydrogen introduced into Mg metal on exposure to water using neutron vibrational spectroscopy techniques. Research sponsored by the DOE Vehicle Technologies Office

I-36: Influence of Thermal Treatment on Corrosion Rates of Mg-RE and Mg-10%Zn-0.3%Ca Alloys in 3.5%NaCl Solution: Marilia Girardi Zorzato1; Joseph Robson1; Dirk Engelberg1; Julie Gough1; 1University of Manchester
    Magnesium alloys are biocompatible materials with suitable mechanical properties for orthopaedic applications. The main driver for their potential use as implant materials is that they will act as temporary implants avoiding stress-shielding effects. However, rapid degradation of magnesium alloys in physiological medium is undesirable for some applications. Degradation must be controlled in order to allow enough time for the body to absorb and/or eliminate corrosion products, and maintain the implant’s mechanical integrity until tissue has sufficiently healed. Application of heat treatments can improve corrosion behaviour of Mg alloys by modifying the metal internal structure. This work aims to evaluate the influence of different thermal treatments on the corrosion rates of a Mg-RE alloy and a Mg-10%Zn-0.3%Ca alloy in 3.5%NaCl solution. Microstructure (grain size and precipitate distribution) of these alloys after solution treatment, ageing and overageing were compared to as-received condition. Potentiodynamic corrosion tests were performed and related to microstructural analysis.

I-38: Magnesium Based Biodegradable Composites for Orthopedic Application: Satish Jaiswal1; Pallavi Gupta1; Partha Roy1; Debrupa Lahiri1; 1Indian Institute of Technology Roorkee
    Magnesium and its alloys have gathered lot of interest as suitable candidates for orthopedic implants and fixing accessories, due to, biodegradability, non-toxicity and mechanical properties, similar to natural bone. The major drawback of magnesium is its low corrosion resistance inside living body, which also influences its mechanical and physical characteristics in service condition. The aim of the present study is to develop a Mg based material system to be used as bone fixing accessories, e.g. screw, nail, plates etc. We achieved that by fabricating composites of Mg and hydroxyapatite (HA). The composite is fabricated through powder consolidation route. The in vitro bio–corrosion (biodegradability) and mechanical behaviors of samples are investigated by electrochemical and compression tests. The experimental results showed that addition of HA could slow down the corrosion rate and improve the mechanical properties of biodegradable magnesium alloy. Biocompatibility of the composites also improves with addition of HA.

I-39: Mechanical and Microstructural Characterization of a Multi-Axis Forged AZ31 Billet: Christian Roach1; Lauren Oh1; Xavier Hernandez1; Suveen Mathaudhu1; 1University of California, Riverside
    Magnesium alloys have gained interest in the transportation sector due to their high strength-to-weight ratio; however, a large percentage of parts used are cast. Wrought processing, such as forging, affords the opportunity for strength improvement but often at the expense of plasticity due to limited slip; thus, approaches that homogenize microstructure and texture are of interest. In this work we report the processing and characterization of AZ31 processed by Multi-Axis Forging (MAF). Microstructure is determined by optical and electron microscopy and texture is found through EBSD. Mechanical properties are assessed in orthogonal directions by instrumented indentation and millimeter-scale tension tests. The results are compared with conventional forged Mg-alloys, and the applicability of MAF for Mg-alloy processing is discussed.

I-40: Microstructures and Tensile Properties of As-cast Magnesium AM60-based Composite Containing Alumina Fibres and Nano Particles: Junxiang Zhou1; Li Fang1; Xuezhi Zhang1; Henry Hu1; 1University of Windsor
    Magnesium alloy AM60 based metal matrix composites (MMCs) reinforced with alumina (Al2O3) fibres and/or nano-size particles were successfully fabricated by preform-squeeze casting techniques under an applied pressure of 90 MPa. Tensile testing was performed and microstructures were analyzed on as-cast unreinforced AM60 Alloy, fibre reinforced AM60 metal matrix composite, and hybrid AM60 composite containing alumina fibres and nano-particles. The microstructure analysis revealed the homogenity of reinforcements in the matrix alloy. With the addition of fibres, the tensile properties of the fibre-reinforced composites were improved with the considerable reduction of ductility compared with AM60 alloy. The introduction of additional nano-particles into the metal matrix not only significantly improved the tensile properties of the composites, but also simultaneously restored the ductility reduction caused by the reinforcement of fibres.

I-41: Negative Difference Effect of Mg Alloy AZ31D in NaCl Solutions: Shuoshuo Xi1; 1University of Illinois at Chicago
    Galvanostatic testing and weight loss measurements are used in the investigation of the Mg alloy AZ31D negative difference effect (NDE) in electrolyte solutions with different concentrations of NaCl. The actual alloy weight loss in galvanostatic tests with different anodic current magnitudes and durations are measured. The actual weight loss is being compared with the theoretical weight loss calculated using Faraday’s law. The AZ31D anodic efficiency is calculated. The actual weight loss is found not being affected by the solution NaCl concentration. The theories of intermediate species, Mg+, and intermetallic particle undermining are discussed as to their contribution to the NDE effect. The working electrode potential variations in the galvanostatic tests are assumed to be related to the process of the corrosion film’s breakdown and growth.

I-42: Origin of Non-Schmid Behavior of {-1011} Deformation Twinning in Mg: Akio Ishii1; Shigenobu Ogata1; 1Osaka University
    The first principles deformation pathway analysis [1] reveals that one of the possible origin of the non-Schmid behavior of {-1011} deformation twinning systems. Among the possible twinning deformation pathway of {-1011} deformation twinning in the systems, such as 4-layer or 2-layer zonal twinning deformation pathway, and so on, we found that the 2-layer zonal twinning deformation pathway[2] is strongly affected by not only the resolved shear stress component in the shearing direction <10-12>(-1011), but also in its normal direction <1-210>(-1011). This is because the computed 2-layer zonal twinning deformation pathway contains the strain component in <1-210>(-1011). The deformation pathway analysis may give a comprehensive understanding of the origin of non-Schmid behaviors in HCP materials. [1] A. Ishii et al., International Journal of Plasticity 82 (2016) pp.32-43; [2] J. Wang et al., Acta Materiallia, 59, (2011) pp.3990-4001.

I-43: Phase Transformations of Long Periodic Stacking Ordered (LPSO) Phases at Finite Temperature in Magnesium-Gadolinium-Aluminum Ternary System: Hongyeun Kim1; Yi Wang1; Laszlo Kecskes2; Kristopher Darling2; Zi-Kui Liu1; 1Pennsylvania State University; 2US Army Research Laboratory
    In this work, Phase Transformations of Long Periodic Stacking Ordered structures (LPSOs) at finite temperature in Mg-Gd-Al ternary system were investigated by first-principles calculations. Here, LPSOs include 10H, 14H, 18R and 24R. We developed stoichiometric LPSO phases that captures L12 clustering of Gd/Al solute atoms with or without interstitial atom at the center of L12 cluster. Thermodynamic properties of LPSO were predicted using Debye model with inputs from first-principles calculations. Debye temperatures were estimated based on the Debye-gruneisen parameter calculations since the shear and Young’s modulus of LPSO increased significantly compared to pure magnesium (α-Mg). Based on the theoretically predicted thermodynamic properties, the phase stabilities of each LPSO phases with layers of α-Mg at 0K and finite temperature range are investigated. We captures that the trends of phase transformations between LPSO phases in terms of L12 cluster building blocks with layers of α-Mg as a function of temperature.

I-44: Production of Mg-Li Alloys by Vacuum Alnminothermic Reduction Process: Wang Yaowu1; Xianwei Hu2; 1 Northeastern University of China; 2Northeastern University of China
    As the lightest metal materials, Mg-Li alloys have a series of advantages and have been widely explored in application of aircraft, electronics and communication industries. At present, most of Mg-Li alloys are produced by mixing magnesium metal and lithium metal which lead to serious burning loss of magnesium and lithium. So the cost of Mg-Li alloys is high. Production of Mg-Li alloys by vacuum alnminothermic reduction process using Li2CO3 and magnesite as materials and aluminum powder as reductant can significantly reduces product cost. It also can produce many different ingredients of Mg-Li alloys. This paper presents you some important data on the process of production of Mg-Li alloys by vacuum alnminothermic reduction.

I-45: Quasi-static and Dynamic Behavior and Microstructure Evolution of WE43 Rare Earth Magnesium Alloy: Experiments and Crystal Plasticity Modeling: Mohammad Jahedi1; Miroslav Zecevic1; Brandon McWilliams2; Irene Beyerlein3; Marko Knezevic1; 1Department of Mechanical Engineering, University of New Hampshire; 2Weapons and Materials Research Directorate, US Army Research Laboratory; 3Department of Mechanical Engineering, Materials Department, University of California at Santa Barbara
    This paper describes the main results from an experimental investigation into the quasi-static and dynamic behavior of rolled and cast WE43 including the anisotropic stress-strain response, strain-hardening rates, tension/compression asymmetry, deformed sample geometry, concomitant evolution of crystallographic texture and deformation twin fraction. The examination is conducted in function of strain rates from 10-3 /s to 105 /s and testing direction. The comprehensive set of data is used to calibrate and validate a strain rate and temperature sensitive multi-scale finite element crystal plasticity model specifically adapted to the behavior of WE43. The same quantities as experimentally characterized are calculated with the model and good agreement is achieved in all aspects. These predictions allowed us to elucidate the role played by various slip and twin mechanisms on the mechanical behavior of WE43 as well as compare it with behavior of other magnesium alloys.

I-47: Strengthening Mechanism of AZ31 Magnesium with Gradient Structure: Maryam Jamalian1; David P. Field1; 1Washington State University
    Gradient structures from nanocrystalline structures in the surface to un-deformed layers cause mechanical incompatibility between different layers, which may lead to superior mechanical properties. The nanocrystalline structure contains nanograins and nanotwins which can be obtained by severe plastic deformation. Shot peening is an effective way of applying severe plastic deformation on the surface of the work-piece for changing the microstructure along the depth. This plastic deformation also leads to formation of mechanical twins for hexagonal close packed (HPC) metals. These structures change mechanical properties that are influenced by the microstructural characteristics. In this study, we investigate the effect of structural modification on AZ31 mechanical properties. Its structure before and after tensile testing are investigated by an optical microscope and field emission scanning electron microscope.

I-48: Study on Electric and Thermal Properties of Mg Alloys with Sn and Ca Elements: Yong-Ho Kim1; Hyo-Sang Yoo1; Chang-Gi Jung1; Hyeon-Taek Son1; 1Korea Institute of Industrial Technology
    Mg alloys on high thermal conductivity and mechanical properties are expected to replace the use of Al alloys in applications. Thermal conductivity influences the performance of alloys as a crucial function and is essential to extend the life of the materials due to uniform temperature distribution. In the present study, we studied effects of Sn addition on microstructure and mechanical properties of Mg-Sn-Ca alloys. Mg-Sn-Ca alloys prepared in crucible under the protection of mixed gas of CO2/0.5%SF6 using commercial stock. The melt was held at 700℃ for 20min and then poured into a mould. And then, as-cast Mg alloys were homogenized that held at 400℃ for 12hours. And homogenized alloys were hot-extruded into a plate that was 4mm in thickness and 50mm in width with a reduction ratio of 18:1. The electric and thermal conductivity of as-cast and as-extruded Mg alloys were investigated with addition of Sn and Ca elements.

I-49: Study on the Reversion Reaction between Magnesium Vapor and CO in the Carbothermic Reduction of Magnesia under Vacuum: Yang Tian1; Baoqiang Xu1; Bin Yang1; Dachun Liu1; Hai Liu1; 1Kunming University of Science and Technology
    In this study, the carbothermic reduction of magnesia under vacuum is experimentally investigated. The phase, surface morphology, and composition of the condensates obtained were examined by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy. The experimental results indicate that the small temperature gradient can improve the direct recovery under the appropriate condensation temperature, and the reversion reaction occurs during the end of condensation due to containing MgO in the profile of the condensation but without MgO in the undersurface of the condensation.

I-50: Surface Integrity Characterization from Shot Peening a Biodegradable Magnesium Alloy: Michael Sealy1; Yuebin Guo2; Ziye Liu2; Chao Li2; 1University of Nebraska-Lincoln; 2The University of Alabama
    Magnesium alloys are promising biodegradable metals for orthopedic and cardiovascular applications. In the past, the critical technical barrier to the success of magnesium implants was how to slow corrosion rates. Numerous investigations showed that varying an alloy’s composition or applying surface coatings can slow corrosion. The new challenge is how to modify the corrosion rate for individual applications or patients. Once approved by a regulatory agency, modifying the composition to manipulate corrosion rates is not feasible due to the risk associated with a new material. Varying a surface coating can manipulate corrosion rates; however, coatings do not enhance the subsurface mechanical properties, and variations may be limited based on the application. Surface treatments, such as laser peening or shot peening, are a promising method to manipulate corrosion rates while improving subsurface mechanical properties. This study investigates surface integrity, such as topography, hardness, and residual stress, after shot peening Mg-Ca.

I-51: Textural Contributions to Strengthening in Mg-RE Alloy with Nanospaced Stacking Faults: Heather Salvador1; Vishnu Bhattacharyya2; Yuntian Zhu3; Sean Agnew2; Suveen Mathaudhu1; 1University of California, Riverside; 2University of Virginia; 3North Carolina State University
    Recent findings in Ti- and Mg-RE alloys have shown high strength when the microstructure is composed of a high-density of stacking faults. The fault formation is posited in part, to be due to the high stresses on boundaries which nucleate the necessary partial dislocations. Deformation to high strains, such as large rolling reductions or severe plastic deformation, is necessary, and suspected to result in textural components that may strongly influence the observed strengthening, however no textural data have been reported in the extant literature. We report on the textural and microstructural evolution in Mg-Gd-Y-Ag-Zr alloy rolled at 450C up to 80% rolling reduction. It is seen that nanospaced stacking faults, and the accompanying high-strength, are only observed at high rolling-reductions, however textural changes are minimal as a function of increased rolling strain. These findings suggest minimal strengthening contributions from texture in hcp systems strengthened by nanoscale faults.

I-52: The Deformation Behavior of Mg-2Zn Alloy Sheet Containing Oxygen Atoms: Seung Won Kang1; Dognhyun Bae1; 1Yonsei University
    The effect of the interstitial oxygen atoms in the magnesium-zinc binary alloy on the grain refinement during annealing treatment and the deformation behavior enhances the failure of elongation. Mg-Zn binary alloy contained randomly distributed oxygen atoms in matrix. And Mg-Zn alloy sheets are given reduction of 25% per pass during rolling. Submicron-grains formed on the micro-grains act additional deformation systems by competitive stress. Unidirectional tensile tests were conducted at room temperature with differential initial strain rate on hot-rolled Mg-2Zn and Mg-O-2Zn alloy sheets, and deformation behavior was investigated from the effect of grain size. The yield point drop is clearly detected at room temperature increased with decrease strain rate in Mg-O-2Zn alloy sheet; in contrast, Mg-2Zn alloy sheet is not detected yield point drop. And Mg-O-2Zn alloy sheet of elongation to failure is enhanced. This phenomenon occurs due to interstitial oxygen that is source of recrystallization formed submicron-size grains.

I-53: The Effect of Annealing on the Properties of AW5754 Aluminium Alloy - AZ31 Magnesium Alloy Joints Produced with Explosion Welding: Martin Sahul1; Miroslav Sahul1; Ján Lokaj1; Petr Nesvadba2; 1Slovak University of Technology in Bratislava; 2OZM Research, Ltd.
    The paper deals with the study of the influence of heat treatment on the properties of AW5754 aluminium alloy - AZ31 magnesium alloy bimetals. Aluminium alloy was selected as the flyer plate. Parallel set up of materials to be welded was selected. Semtex S30 loose explosive was used for explosion welding of dissimilar metals. Heat treatment of produced AW5754/AZ31 bimetals at the temperatures of 250, 300 and 450 °C for 2, 3, 4 and 5 hours was performed after explosion welding process. Scanning electron microscopy fitted with EDX analysis and microhardness measurements across bimetals interface was used to analyze the weld joints properties before and after heat treatment.

I-54: Grain Refining in Mg Welds with Arc Oscillation: Tao Yuan1; Shujun Chen1; Sindo Kou; 1Beijing University of Technology
    Grain refining can improve the solidification-cracking resistance during welding and mechanical properties of the resultant weld. AZ31 Mg and AZ91 Mg alloy were welded by gas-tungsten arc welding with arc oscillation (transverse, longitude and circular) at 1 Hz frequency and 2 mm amplitude. Significant grain refining was achieved with all 3 different kinds of oscillation. The following observations were made. First, the grain refining of AZ31 Mg welds increased with increasing oscillation frequency. However, grain refining disappeared when the frequency exceeded 25Hz. Second, the grain refining of AZ91 Mg welds was more significant than AZ31 Mg welds. Third, the grain refining mechanism was identified as dendrite fragmentation, instead of heterogeneous nucleation or grain detachment. Fourth, transverse arc oscillation not only caused dendrite fragmentation but also increased constitutional supercooling.