Magnesium Technology: On-Demand Poster Session
Sponsored by: TMS Light Metals Division, TMS: Magnesium Committee
Program Organizers: Petra Maier, University of Applied Sciences Stralsund; Steven Barela, Terves, Inc; Victoria Miller, University of Florida; Neale Neelameggham, IND LLC
Monday 8:00 AM
March 14, 2022
Room: Light Metals
Location: On-Demand Poster Hall
Effect of CO2 Annealing Treatments on Corrosion Behavior of AZ91D Mg Alloy: Gyoung Gug Jang1; Jiheon Jun1; Michael Brady1; 1Oak Ridge National Laboratory
Application of Mg alloys as structural components of vehicle can improve the energy efficiency. However, the poor corrosion resistance of Mg alloy is one of the major bottlenecks to limit wide vehicle application including vehicle frames. An electrically-insulating layer can be formed from Mg alloy surface to mitigate corrosion. To achieve such an insulating surface, AZ91D Mg alloy was treated by an exploratory treatment method, CO2 annealing with pre-loaded salts to grow carbonate crystalline insulation layers providing corrosion protection for the underlaying AZ91D. The engineered MgO layer on Mg surfaces can absorb CO2 via salt facilitation to form an insulting MgCO3 layer. Currently, systematic surface treatments are underway on AZ91D coupons to facilitate the corrosion protective layer formation. The surface-treated AZ91D samples will be characterized by electrochemical corrosion evaluation. Also, the chemical compositions and microstructure in the surface and sub-surface regions will be characterized, and the results will be reported.
Effect of Different Mold Materials on the Solidification Rate and Microstructure of Magnesium Alloy Plate Castings: Amjad Javaid1; 1Natural Resources Canada
Although the magnesium sheet shows promising applications in automotive, aerospace, and electronic housing industries, its development is still limited due to the present manufacturing barriers. During a production of magnesium plates, as precursors for sheet rolling, the frequently overlooked factor is the effectiveness of commonly used mold materials in controlling the cooling rate thereby increasing or decreasing the solidification time, the riser size and casting defects. The objective of this study was to cast magnesium alloy plates with different cooling rates to determine the effect of cast structure on the resulting sheet properties and microstructure. For this purpose a 6 mm thick AZ31B plate was cast by gravity, vacuum and twin roll casting methods in permanent (graphite and metal molds) and sand molds (silica, carbo ceramics, and olivine). The microstructure of the plate was studied and secondary dendrite arm spacing (SDAS) was measured utilizing quantitative metallography techniques and image analysis. The obtained results, including the relationship between SDAS and cooling rate were compared with the literature data. As the cooling rate increased, the SDAS decreased and microstructure became finer. Because of this work, magnesium plates were produced for rolling purposes that have different cast structures, with SDAS’s ranging from 4.5 – 40 micron.
Role of Ca & Y in Corrosion Resistance of SEN Magnesium Alloys: Bong Sun You1; Sang Kyu Woo2; Young Min Kim1; 1Korea Institute of Materials Science; 2Helmholtz–Zentrum Geesthacht, Max-Planck-Straße 1, Geesthacht
Lots of studies have been done for the development of new oxidation resistant or corrosion resistant magnesium alloys by the addition of minor elements which make dense oxide film preferentially on the surface and act as protective layer for the rapid oxidation at high temperature or corrosion environment. SEN alloy containing small amount of Ca and Y in AZ series alloy, initially designed for non-flammable alloy, has been reported to have excellent corrosion resistance. However, the mechanism of improved corrosion resistance of SEN alloy is not explained clearly. In this paper, corrosion behavior of SEN alloys made by various different process and tested in various corrosion environment was summarized in detail, and two approaches to explain excellent corrosion resistance of SEN alloys were suggested.
Twinning, Detwinning and Crack Initiation in Compression-compression Fatigue of Extruded Magnesium Alloy AZ31: Yoshikazu Nakai1; Shoichi Kikuchi2; Kaito Asayama1; Hayata Yoshida1; 1Kobe University; 2Shizuoka University
Several types of cyclic stress were applied to specimens made of an extruded magnesium alloy, AZ31, to elucidate twinning, detwinning, and fatigue crack initiation mechanisms by EBSD analysis. In both the texture and the random orientation, twinning occurred under compressive stress exceeding the compressive yield strength. Detwinning occurred only in the texture upon the subsequent application of tensile stress less than the tensile yield strength of monotonic loading, whereas detwinning did not occur in the structure with random orientation. Under compression-compression fatigue test, successive twinning occurred, which changed the orientation of the basal plane. As a result, the random orientation of grains changed to the texture in which the normal of the basal plane was parallel to the loading direction. Cracks were formed along the boundary of grains with a high Schmid factor of the basal slip system and the misfit of grain on both sides was large.
The Effects of Annealing Treatment on Microstructure and Mechanical Properties of the Extruded Mg-1.3Zn-0.5Ca Alloy: Honglin Zhang1; Zhigang Xu1; Sergey Yarmolenko1; Jagannathan Sankar1; 1North Carolina Agricultural and Technical State University
In the present study, the Mg-1.3Zn-0.5Ca (wt.%) magnesium alloy was hot extruded and subsequently annealed at 300°C, 350°C, and 400°C for different holding times to optimize microstructure and mechanical properties. The results show that the bimodal microstructure is the main feature of the as-extruded Mg-1.3Zn-0.5Ca alloy, which can be described as the elongated grains are surrounded by the fine dynamic recrystallized (DRXed) grains. Moreover, the as-extruded alloy shows a strong {10-10} fiber texture, especially for the large elongated grains. The annealing treatment results in static recrystallization, which increases fine equiaxed grains but decreases large elongated grains. In addition, the equiaxed grains formed during the annealing treatment weaken the {10-10} fiber texture of the alloy. Also, the annealing treatment could increase the yield and ultimate strength, but the elongation decreases, especially at a higher temperature, which can be ascribed to the evolution of microstructure and texture.
Effect of Single Pass Differential Speed Rolling on the Dynamic Recrystallization, Microstructure and Mechanical Properties of Mg5Zn: Christopher Hale1; 1North Carolina Agricultural and Technical State University
Single pass differential speed rolling of magnesium zinc alloys (Mg5Zn) has been investigated to determine the role of dynamic recrystallization (DRX) on the grain refinement and corresponding mechanical properties. The study has shown that DRX grain size decreased with increased rolling reduction as well as various characteristics pertaining to grain refinement of the ultrafine and partially recrystallized grains. Evaluation of the microstructure was performed through optical microscopy and scanning electron microscopy / electron backscatter diffraction to evaluate the effect of DRX on grain size. Alternatively, a decrease in grain size showed an expected upward trend of increasing tensile strength and hardness with increased rolling reduction.
Cancelled
Constitutive Modeling of Rolled AZ31 Magnesium with Temperature and Texture Dependence: Daniel Kenney1; Marcos Lugo1; Jared Darius1; 1Liberty University
Magnesium alloys have a crucial role as a lightweight structural material in the effort to reduce vehicle weight and increase fuel efficiency. With a lower melting temperature than most structural metals, and a Hexagonal Close-Packed atomic structure, the behavior of many wrought magnesium alloys is highly dependent on temperature and loading direction. This research investigates the behavior of a rolled AZ31 sheet under quasi-static monotonic tensile loading to understand the effects of temperature and orientation on deformation twinning and failure mechanisms. Specimens are manufactured in the longitudinal and transverse directions to evaluate the effects of texture. A microstructural analysis characterizes the distribution of grain size, particles, and critical defects in each direction. Tests are run at room temperature, 100 C, and 200 C for both texture orientations. An internal state variable constitutive model is implemented which incorporates the effects of microstructure and temperature to characterize material deformation mechanisms.