The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Kwang Seon Shin - One of the best experts on this subject based on the ideXlab platform.
-
Semi-Solid Processing of Magnesium Alloys
Materials Science Forum, 2009Co-Authors: Dong Yim Chang, Jae-chul Lee, Hyun-kwang Seok, Kwang Seon ShinAbstract:Semi-solid processing is an emerging technology for near net-shape production of engineering components. Although there has been a significant progress in semi-solid processing of Al alloys, very limited information is available on semi-solid processing of Mg alloys, except for the Thixomolding process. In semi-solid casting process, it is necessary to properly control the flow and solidification behavior of semi-solid slurries for high quality products. There are a number of parameters that affect the flow and solidification behavior of semi-solid slurries such as viscosity, casting pressure, shapes of gate and mold cavity, gate velocity, mold temperature, etc. In the present study, the effects of various thermo-mechanical treatments were investigated on the change in viscosity of the semi-solid AZ91D magnesium alloys by using a concentric cylinder type viscometer. The effects of gate velocity and thickness on mold filling behavior of the semi-solid AZ91D alloys were also investigated by using a high-speed camera and the results were compared with those obtained from computer simulations. From these results and microstructure examination, a processing map for high pressure die casting of the semi-solid AZ91D alloy was constructed in order to produce the sound casting.
-
Continuous Casting of Magnesium Billets for Semi-Solid Processing
Materials Science Forum, 2005Co-Authors: Hwa Chul Jung, Kwang Seon ShinAbstract:Semi-solid processing is recognized as an attractive alternative method for the near net-shape production of engineering components. Although there has been a significant progress in semi-solid processing of aluminum alloys, very limited information is available on semi-solid processing of magnesium alloys, except for the Thixomolding process. Continuous casting process has been utilized to produce the billets with the desirable cross-section at a reduced production cost for many metals, such as steel, copper and aluminum alloys. It has also been commercially utilized to produce the aluminum billets with non-dendritic microstructure for subsequent thixocasting process. However, continuous casting of magnesium billets for semi-solid processing has not yet been commercialized due to the difficulties involved in casting of magnesium alloys. In the present study, a continuous casting process has been developed for the production of the cylindrical billets of magnesium alloys for the subsequent thixocasting process. In order to obtain the desired non-dendritic microstructure with an excellent degree of homogeneity both in microstructure and composition, an electromagnetic stirring system has been utilized. A continuous casting process has been proven to be an efficient way to produce the high quality billets of magnesium alloys for semi-solid processing. A prototype air conditioner cover was produced using the continuously cast billets of AZ91 alloy.
-
Semi-Solid Processing of Magnesium Alloys
Materials Transactions, 2003Co-Authors: Kwang Seon ShinAbstract:Semi-solid processing is an emerging technology for near net-shape production of engineering components. Although there has been significant progress in semi-solid processing of Al alloys, very limited information is available on semi-solid processing of Mg alloys, except for the Thixomolding process. In semi-solid casting process, it is necessary to properly control the flow and solidification behavior of semi-solid slurries for high quality products. There are a number of parameters that affect the flow and solidification behavior of semi-solid slurries such as viscosity, casting pressure, shapes of gate and mold cavity, gate velocity, mold temperature, etc. In the present study, the effects of various thermo-mechanical treatments were investigated on the change in viscosity of the semi-solid AZ91D magnesium alloys by using a concentric cylinder type viscometer. The effects of gate velocity and thickness on mold filling behavior of the semi-solid AZ91D alloys were also investigated by using a high-speed camera and the results were compared with those obtained from computer simulations. From these results and microstructure examination, a processing map for high pressure die casting of the semi-solid AZ91D alloy was constructed in order to produce sound castings.
-
Semi-solid processing of magnesium alloys : Special issue on platform science and technology for advanced magnesium alloys, II
Materials Transactions Jim, 2003Co-Authors: Kwang Seon ShinAbstract:Semi-solid processing is an emerging technology for near net-shape production of engineering components. Although there has been significant progress in semi-solid processing of Al alloys, very limited information is available on semi-solid processing of Mg alloys, except for the Thixomolding process. In semi-solid casting process, it is necessary to properly control the flow and solidification behavior of semi-solid slurries for high quality products. There are a number of parameters that affect the flow and solidification behavior of semi-solid slurries such as viscosity, casting pressure, shapes of gate and mold cavity, gate velocity, mold temperature, etc. In the present study, the effects of various thermo-mechanical treatments were investigated on the change in viscosity of the semi-solid AZ91D magnesium alloys by using a concentric cylinder type viscometer. The effects of gate velocity and thickness on mold filling behavior of the semi-solid AZ91D alloys were also investigated by using a high-speed camera and the results were compared with those obtained from computer simulations. From these results and microstructure examination, a processing map for high pressure die casting of the semi-solid AZ9 ID alloy was constructed in order to produce sound castings.
F Czerwinski - One of the best experts on this subject based on the ideXlab platform.
-
microstructure control during Thixomolding of magnesium alloys
Journal of Advanced Materials, 2006Co-Authors: F CzerwinskiAbstract:Mg-9%Al-1%Zn alloy, in the form of mechanically comminuted chips, was processed using a Thixomolding® system at temperatures below and above the liquidus. The results showed that the feedstock nature in a combination with the temperature profile along the alloy flow path control its transformations in a semisolid state and, in a consequence, the microstructure after solidification. Examples of molding microstructures for Mg-9%Al-1%Zn alloy are analyzed.
-
magnesium alloy particulates for Thixomolding applications manufactured by rapid solidification
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: F CzerwinskiAbstract:Abstract Techniques based on a rapid solidification concept were explored for manufacturing particulates of magnesium alloys with the potential use as feedstock for Thixomolding ® . Basic features of granulation methods are outlined along with dimensional, morphological, microstructural and chemical characterizations of particulates with a composition of Mg–9% Al–1% Zn. In spite of the known tendency of Mg and Zn to evaporate, the globule chemistry was within the alloy’s specification. The microstructure comprised of dendritic morphologies of α-Mg and Mg 17 Al 12 phases where the content of the latter was reduced compared to the conventionally cast state. It is suggested that the microchemical and phase segregations which accompanied the morphology of fine equiaxed dendrites are the key factors which control the transformation of particulates during subsequent heating in a solid state and their melting behaviour.
T. D. Berman - One of the best experts on this subject based on the ideXlab platform.
-
Thermomechanical Processing of Thixomolded Alloys
The Minerals Metals & Materials Series, 2017Co-Authors: R. F. Decker, Nir Moskovich, Stephen Lebeau, T. D. Berman, Tresa M Pollock, Tori Miller, J. Wayne Jones, Boris BronfinAbstract:A wide variety of Mg alloys have been processed by Thixomolding ® followed by thermomechanical processing (TMP)—to increase tensile, creep and fatigue strength, ductility and formability. These alloys encompass variations in Al, Zn, Ca, Mn, Sr, Y, Zr and Rare Earths (RE) in the Mg base. Due to the fine microstructure and low porosity rendered by Thixomolding, TMP has been feasible using high strain warm rolling and warm pressing. Thus, grain size is further reduced and texture can be moderated. Data is presented on the above alloys along with more extensive information on the commercial alloys AM60 and AZ61; but also the newly developed AZ70L-TH and AXJ810-TH alloys. In discussing the above processing, properties are related to microstructures.
-
microstructure and texture through Thixomolding and thermomechanical processing and the role of mg17al12 particles
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: T. D. Berman, Tresa M Pollock, Wayne J JonesAbstract:Thixomolding and thermomechanical processing (TTMP) is a pathway through which it is possible to produce Mg alloy sheet with both a fine grain size and a weak basal texture. Following static recrystallization, the texture of TTMP AZ61 is comparable to that of rare-earth Mg alloy sheets. The β-Mg17Al12 particles in the alloy serve several important roles. Pinning during rolling retards dynamic recrystallization, thereby preventing the development of the typical Mg sheet deformation texture. Recrystallized grains form near clusters of β-particles and in the grain mantle regions. Larger β-particles pin boundaries during subsolvus thermal exposures and therefore provide grain size stability during annealing. The size and spatial arrangement of the β-particles are relatively stable during processing, so modifications to optimize the texture reduction or grain size stability would require changes in composition or modifications in the Thixomolding parameters.
-
Magnesium Technology 2014 - Effect of microstructure on deformation and fracture of thixomolded and thermomechanically Processed AZ61
Magnesium Technology 2014, 2014Co-Authors: T. D. Berman, W. Donlon, R. F. Decker, Tresa M Pollock, J. W. JonesAbstract:This paper investigates the deformation, damage accumulation and fracture behavior of fine-grained AZ61 sheet produced by combined Thixomolding and Thermomechanical (TTMP) processing. In the TTMP process, warm rolling of a fine-grained, untextured Thixomolded plate with subsequent recrystallizion produces a sheet with an α-Mg grain size of 3 to 5 μm and s-particles with an average diameter of 0.5 μm. The fine grain size and weak texture in the sheet results in nearly isotropic mechanical properties. Damage during tensile straining occurs in the form of cracking in the s-particles in both the as-Thixomolded plate precursor and in the recrystallized sheet. However, the material fails due to strain localization in shear bands and microvoid coalescence.
-
Magnesium Technology 2013 - Microstructure Characterization of Weakly Textured and Fine Grained AZ61 Sheet
Magnesium Technology 2013, 2013Co-Authors: T. D. Berman, W. Donlon, R. F. Decker, Tresa M Pollock, C. K. Hung, P. Milligan, J. W. JonesAbstract:Formability in magnesium alloy sheet is strongly limited by a strong basal texture in the as-rolled material, which is difficulty to remove by thermal processing. We introduce a new process to the control of texture by combining Thixomolding and Thermomechanical Processing (TTMP). Plates of AZ61L with a divorced β-Mg17Al12 eutectic are produced by Thixomolding, resulting in a non-textured, fine grained (2.8 µm) precursor. Sheet produced from the plate by single pass warm-rolling exhibits a weaker texture, and more isotropic tensile deformation than generally observed in AZ-series alloy sheet. Recrystallization annealing produces a further reduction in texture and average grain size (2.3 µm) and results in nearly isotropic room temperature deformation, a yield strength of ~ 220 MPa, and an elongation of ~ 23%. Particle stimulated nucleation of new grains by the β-phase during both dynamic and static recrystallization, is critical for achieving the low levels of texture. The influence of β-phase distribution in microstructure development is discussed.
-
microstructure modification and deformation behavior of fine grained az61l sheet produced by Thixomolding and thermomechanical processing
Magnesium Technology 2012 - TMS 2012 Annual Meeting and Exhibition, 2012Co-Authors: T. D. Berman, W. Donlon, Tresa M Pollock, R Decker, J. Huang, V M Miller, J. W. JonesAbstract:X-ray diffraction and hardness measurements are used to study recrystallization in fine-grained AZ61L sheet produced by warm-rolling of Thixomolded® material. The as-rolled sheet is partially dynamically-recrystallized, with a strong basal texture and a sub-micron grain size. Significant increases in ductility with moderate reductions in tensile strength were produced by annealing at temperatures greater than 250 °C. A weakening in basal texture was observed in samples annealed at over 250°C. Static recrystallization was determined to be responsible for the reduction in texture and associated increase in elongation.
Tresa M Pollock - One of the best experts on this subject based on the ideXlab platform.
-
Thermomechanical Processing of Thixomolded Alloys
The Minerals Metals & Materials Series, 2017Co-Authors: R. F. Decker, Nir Moskovich, Stephen Lebeau, T. D. Berman, Tresa M Pollock, Tori Miller, J. Wayne Jones, Boris BronfinAbstract:A wide variety of Mg alloys have been processed by Thixomolding ® followed by thermomechanical processing (TMP)—to increase tensile, creep and fatigue strength, ductility and formability. These alloys encompass variations in Al, Zn, Ca, Mn, Sr, Y, Zr and Rare Earths (RE) in the Mg base. Due to the fine microstructure and low porosity rendered by Thixomolding, TMP has been feasible using high strain warm rolling and warm pressing. Thus, grain size is further reduced and texture can be moderated. Data is presented on the above alloys along with more extensive information on the commercial alloys AM60 and AZ61; but also the newly developed AZ70L-TH and AXJ810-TH alloys. In discussing the above processing, properties are related to microstructures.
-
Microstructure and Texture Through Thixomolding and Thermomechanical Processing and the Role of Mg_17Al_12 Particles
Metallurgical and Materials Transactions A, 2016Co-Authors: Tracy D. Berman, Tresa M Pollock, J. Wayne JonesAbstract:Thixomolding and thermomechanical processing (TTMP) is a pathway through which it is possible to produce Mg alloy sheet with both a fine grain size and a weak basal texture. Following static recrystallization, the texture of TTMP AZ61 is comparable to that of rare-earth Mg alloy sheets. The β -Mg_17Al_12 particles in the alloy serve several important roles. Pinning during rolling retards dynamic recrystallization, thereby preventing the development of the typical Mg sheet deformation texture. Recrystallized grains form near clusters of β -particles and in the grain mantle regions. Larger β -particles pin boundaries during subsolvus thermal exposures and therefore provide grain size stability during annealing. The size and spatial arrangement of the β -particles are relatively stable during processing, so modifications to optimize the texture reduction or grain size stability would require changes in composition or modifications in the Thixomolding parameters.
-
microstructure and texture through Thixomolding and thermomechanical processing and the role of mg17al12 particles
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2016Co-Authors: T. D. Berman, Tresa M Pollock, Wayne J JonesAbstract:Thixomolding and thermomechanical processing (TTMP) is a pathway through which it is possible to produce Mg alloy sheet with both a fine grain size and a weak basal texture. Following static recrystallization, the texture of TTMP AZ61 is comparable to that of rare-earth Mg alloy sheets. The β-Mg17Al12 particles in the alloy serve several important roles. Pinning during rolling retards dynamic recrystallization, thereby preventing the development of the typical Mg sheet deformation texture. Recrystallized grains form near clusters of β-particles and in the grain mantle regions. Larger β-particles pin boundaries during subsolvus thermal exposures and therefore provide grain size stability during annealing. The size and spatial arrangement of the β-particles are relatively stable during processing, so modifications to optimize the texture reduction or grain size stability would require changes in composition or modifications in the Thixomolding parameters.
-
Magnesium Technology 2014 - Effect of microstructure on deformation and fracture of thixomolded and thermomechanically Processed AZ61
Magnesium Technology 2014, 2014Co-Authors: T. D. Berman, W. Donlon, R. F. Decker, Tresa M Pollock, J. W. JonesAbstract:This paper investigates the deformation, damage accumulation and fracture behavior of fine-grained AZ61 sheet produced by combined Thixomolding and Thermomechanical (TTMP) processing. In the TTMP process, warm rolling of a fine-grained, untextured Thixomolded plate with subsequent recrystallizion produces a sheet with an α-Mg grain size of 3 to 5 μm and s-particles with an average diameter of 0.5 μm. The fine grain size and weak texture in the sheet results in nearly isotropic mechanical properties. Damage during tensile straining occurs in the form of cracking in the s-particles in both the as-Thixomolded plate precursor and in the recrystallized sheet. However, the material fails due to strain localization in shear bands and microvoid coalescence.
-
Magnesium Technology 2013 - Microstructure Characterization of Weakly Textured and Fine Grained AZ61 Sheet
Magnesium Technology 2013, 2013Co-Authors: T. D. Berman, W. Donlon, R. F. Decker, Tresa M Pollock, C. K. Hung, P. Milligan, J. W. JonesAbstract:Formability in magnesium alloy sheet is strongly limited by a strong basal texture in the as-rolled material, which is difficulty to remove by thermal processing. We introduce a new process to the control of texture by combining Thixomolding and Thermomechanical Processing (TTMP). Plates of AZ61L with a divorced β-Mg17Al12 eutectic are produced by Thixomolding, resulting in a non-textured, fine grained (2.8 µm) precursor. Sheet produced from the plate by single pass warm-rolling exhibits a weaker texture, and more isotropic tensile deformation than generally observed in AZ-series alloy sheet. Recrystallization annealing produces a further reduction in texture and average grain size (2.3 µm) and results in nearly isotropic room temperature deformation, a yield strength of ~ 220 MPa, and an elongation of ~ 23%. Particle stimulated nucleation of new grains by the β-phase during both dynamic and static recrystallization, is critical for achieving the low levels of texture. The influence of β-phase distribution in microstructure development is discussed.
Jean-françois Moisan - One of the best experts on this subject based on the ideXlab platform.
-
Mold Filling Simulation of Semi-Solid Magnesium Alloys
Solid State Phenomena, 2008Co-Authors: Florin Ilinca, Frank Ajersch, J.-f. Hétu, Jean-françois MoisanAbstract:Magnesium alloys are increasingly used in automotive, aeronautic and electronic applications to produce high performance, light weight parts. In the Thixomolding process the semisolid slurry is injected into a mold at controlled temperature such that the melt has specific flow behavior. This allows the fabrication of near net shape components with controlled microstructure and good mechanical properties. The numerical modeling of such applications presents unusual challenges for both the physical modeling and the solution algorithm. This paper presents 3D solutions of the injection molding of semi-solid AZ91 magnesium alloys. The methodology deals with the shear thinning, temperature dependent viscosity behavior and is able to accurately solve the high velocity flows encountered during semi-solid magnesium molding. The approach is applied to the injection of a tensile bar and the results compared with experimental data. The numerical solutions indicate that the material forms a jet at the exit of the gate and a swirling flow forms as the material advances along the first larger diameter section. The wall regions are filled first, leaving a void inside. This agrees very well with the experimental observation.
-
Three-dimensional injection molding simulation of AZ91D semi-solid magnesium alloy
International Journal of Material Forming, 2008Co-Authors: Florin Ilinca, Jean-françois Moisan, J.-f. Hétu, Frank AjerschAbstract:Magnesium alloys are increasingly used in automotive, aeronautic and electronic applications to produce high performance, light weight parts. In the Thixomolding process a semi-solid slurry is injected into a mold at controlled temperature such that the melt has specific flow behavior. This allows the fabrication of near net shape components with controlled microstructure and good mechanical properties. The numerical modeling of such applications present unusual challenges for both the physical modelling and the solution algorithm. This paper presents a 3D numerical solution algorithm for the simulation of the injection molding of semi-solid AZ91 magnesium alloys. The methodology deals with the shear thinning, temperature dependent viscosity behavior and is able to accurately solve the high velocity flows encountered during semi-solid magnesium molding. A segregated algorithm is used to solve the Navier–Stokes, energy and front tracking equations. The position of the flow front in the mold cavity is computed using a level set approach. Equations are integrated in time using an implicit Euler scheme and solved by stabilized finite element methods. The approach is applied to the injection of a tensile bar and the results compared with experimental data. The methodology presents the robustness and cost effectiveness needed to tackle complex industrial applications.