Modeling and Simulation of Microstructure Evolution of Cast Mg Alloy

2010 ◽  
Vol 638-642 ◽  
pp. 1562-1568 ◽  
Author(s):  
Liang Huo ◽  
Zhi Qiang Han ◽  
Bai Cheng Liu
Keyword(s):  
Solute Transport ◽  
Magnesium Alloys ◽  
Microstructure Evolution ◽  
Local Equilibrium ◽  
Equilibrium Composition ◽  
Mg Alloy ◽  
Dendrite Morphology ◽  
Dendrites Growth ◽  
The Difference ◽  
Cast Magnesium

A cellular automaton (CA) model has been developed for simulating the microstructure evolution and dendrite morphology of cast magnesium alloys. The growth kinetics of dendrite tips is determined by the difference between local equilibrium composition and local actual composition obtained by solving the solute transport equation. Two sets of meshes, a hexagonal mesh and an orthogonal mesh, are used in the model to perform the simulation. The hexagonal mesh is used to perform CA calculation to reflect the texture of Mg alloy dendrites, and the orthogonal mesh is used to solve the solute transport equations. The model was applied to simulate single dendrite evolution and columnar dendrites growth of AZ91D Mg alloy, as well as multi-grain growth of Mg-10Gd-2Y-0.5Zr (wt%) Mg alloy. Permanent mold step-shaped castings of the two Mg alloys were poured and metallographic examinations were carried out for validating the present model. The simulation results agree well with metallographic results. The model can be applied to simulate the microstructure evolution and dendrite morphology of magnesium alloys.

Three-Dimensional Modeling and Simulation of Dendrite Morphology of Cast Mg Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 1516-1519 ◽  
Author(s):  
Liang Huo ◽  
Zhi Qiang Han ◽  
Bai Cheng Liu
Keyword(s):  
Interpolation Method ◽  
Local Equilibrium ◽  
Three Dimensional ◽  
Equilibrium Composition ◽  
Mg Alloys ◽  
Az91d Alloy ◽  
Dendrite Morphology ◽  
Three Dimensional Modeling ◽  
The Difference ◽  
Permanent Mold Castings

A three-dimensional (3-D) cellular automaton (CA) model for simulating the dendrite morphology of cast Mg alloys has been developed. In the model a technique based on two sets of mesh is utilized to perform the simulation to reproduce the texture of Mg dendrites. The CA calculation is performed using a set of mesh that is defined by the hexagonal close-packed (HCP) crystal lattice, and other computations are carried out by using a cubic mesh. The two sets of mesh are coupled by using interpolation method. The kinetics of the solid-liquid interface is obtained directly by the difference between local equilibrium composition and local actual composition given by the solute transport equation. The model was used to simulate 3-D columnar growth of sixteen grains and 3-D equiaxed growth of a single dendrite of AZ91D alloy. Permanent mold castings of AZ91D alloy were produced and sampled for optical metallographic examinations, and the simulated results were compared with the metallographic results.

Surface Microstructure Evolution Upon Silicidation of Ni(Pt) and the Different Responses to Metal Etch

2013 ◽  
Author(s):  
Wentao Qin ◽  
Dorai Iyer ◽  
Jim Morgan ◽  
Carroll Casteel ◽  
Robert Watkins ◽  
...  
Keyword(s):  
Thin Film ◽  
Oxide Film ◽  
Microstructure Evolution ◽  
Depth Profiling ◽  
Surface Microstructure ◽  
The Difference ◽  
Surface Microstructures ◽  
Pt Films

Abstract Ni(5 at.%Pt ) films were silicided at a temperature below 400 °C and at 550 °C. The two silicidation temperatures had produced different responses to the subsequent metal etch. Catastrophic removal of the silicide was seen with the low silicidation temperature, while the desired etch selectivity was achieved with the high silicidation temperature. The surface microstructures developed were characterized with TEM and Auger depth profiling. The data correlate with both silicidation temperatures and ultimately the difference in the response to the metal etch. With the high silicidation temperature, there existed a thin Si-oxide film that was close to the surface and embedded with particles which contain metals. This thin film is expected to contribute significantly to the desired etch selectivity. The formation of this layer is interpreted thermodynamically.

scholarly journals Reaction of Chalcones with Cellular Thiols. The Effect of the 4-Substitution of Chalcones and Protonation State of the Thiols on the Addition Process. Diastereoselective Thiol Addition

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4332
Author(s):  
Fatemeh Kenari ◽  
Szilárd Molnár ◽  
Pál Perjési
Keyword(s):  
Biological Effects ◽  
Equilibrium Composition ◽  
Deprotonated Form ◽  
Degree Of Ionization ◽  
Thiol Reactivity ◽  
Michael Type Addition ◽  
Ph Conditions ◽  
The Difference ◽  
Initial Reactivity

Several biological effects of chalcones have been reported to be associated with their thiol reactivity. In vivo, the reactions can result in the formation of small-molecule or protein thiol adducts. Both types of reactions can play a role in the biological effects of this class of compounds. Progress of the reaction of 4-methyl- and 4-methoxychalcone with glutathione and N-acetylcysteine was studied by the HPLC-UV-VIS method. The reactions were conducted under three different pH conditions. HPLC-MS measurements confirmed the structure of the formed adducts. The chalcones reacted with both thiols under all incubation conditions. The initial rate and composition of the equilibrium mixtures depended on the ratio of the deprotonated form of the thiols. In the reaction of 4-methoxychalcone with N-acetylcysteine under strongly basic conditions, transformation of the kinetic adduct into the thermodynamically more stable one was observed. Addition of S-protonated N-acetylcysteine onto the polar double bonds of the chalcones showed different degrees of diastereoselectivity. Both chalcones showed a Michael-type addition reaction with the ionized and non-ionized forms of the investigated thiols. The initial reactivity of the chalcones and the equilibrium composition of the incubates showed a positive correlation with the degree of ionization of the thiols. Conversions showed systematic differences under each set of conditions. The observed differences can hint at the difference in reported biological actions of 4-methyl- and 4-methoxy-substituted chalcones.

Long Term Creep Properties of a Die-Cast Mg-Al-Ca Alloy

2007 ◽  
Vol 561-565 ◽  
pp. 163-166
Author(s):  
Yoshihiro Terada ◽  
Tatsuo Sato
Keyword(s):  
Creep Rate ◽  
Magnesium Alloys ◽  
Cast Alloy ◽  
Rupture Life ◽  
Testing Temperature ◽  
Creep Rupture ◽  
Die Cast ◽  
Cast Magnesium Alloys ◽  
Term Creep ◽  
Cast Magnesium

Creep rupture tests were performed for a die-cast Mg-Al-Ca alloy AX52 (X representing calcium) at 29 kinds of creep conditions in the temperature range between 423 and 498 K. The creep curve for the alloy is characterized by a minimum in the creep rate followed by an accelerating stage. The minimum creep rate (ε& m) and the creep rupture life (trup) follow the phenomenological Monkman-Grant relationship; trup = C0 /ε& m m. It is found for the AX52 die-cast alloy that the exponent m is unity and the constant C0 is 2.0 x 10-2, independent of creep testing temperature. The values of m and C0 are compared with those for another die-cast magnesium alloys. The value m=1 is generally detected for die-cast magnesium alloys. On the contrary, the value of C0 sensitively depends on alloy composition, which is reduced with increasing the concentration of alloying elements such as Al, Zn and Ca.

Comparison of As-Cast Microstructures and Mechanical Properties for Mg-Ce-Mn-Sc and Mg-Ce-Mn-Zn Magnesium Alloys

2009 ◽  
Vol 610-613 ◽  
pp. 746-749 ◽  
Author(s):  
Jia Shen ◽  
Ming Bo Yang ◽  
Fu Sheng Pan ◽  
Ren Ju Cheng
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloys ◽  
Creep Properties ◽  
Microstructures And Mechanical Properties ◽  
The Difference ◽  
Cast Microstructure

The as-cast microstructures and mechanical properties of Mg-3Ce-1.2Mn-0.9Sc and Mg-3Ce-1.2Mn-1Zn magnesium alloys were investigated and compared. The results indicate that the as-cast microstructure of Mg-3Ce-1.2Mn-0.9Sc alloy was mainly composed of -Mg, Mg12Ce and Mn2Sc phases, and that the as-cast microstructure of Mg-3Ce-1.2Mn-1Zn alloy was mainly composed of -Mg, Mg12Ce and MgZn phases. In addition, the as-cast tensile and creep properties of Mg-3Ce-1.2Mn-0.9Sc alloy were higher than that of the Mg-3Ce-1.2Mn-1Zn alloy. The difference of the two alloys in as-cast tensile and creep properties may be related to the initial microstructures of the two alloys.

Investigations on Microstructure Evolution and Deformation Behavior of Aged and Ultrafine Grained Al-Zn-Mg Alloy Subjected to Severe Plastic Deformation

2010 ◽  
Vol 667-669 ◽  
pp. 253-258
Author(s):  
Wei Ping Hu ◽  
Si Yuan Zhang ◽  
Xiao Yu He ◽  
Zhen Yang Liu ◽  
Rolf Berghammer ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Severe Plastic Deformation ◽  
Microstructure Evolution ◽  
Deformation Behavior ◽  
Deformation Mechanisms ◽  
Mg Alloy ◽  
Ultrafine Grained

An aged Al-5Zn-1.6Mg alloy with fine η' precipitates was grain refined to ~100 nm grain size by severe plastic deformation (SPD). Microstructure evolution during SPD and mechanical behaviour after SPD of the alloy were characterized by electron microscopy and tensile, compression as well as nanoindentation tests. The influence of η' precipitates on microstructure and mechanical properties of ultrafine grained Al-Zn-Mg alloy is discussed with respect to their effect on dislocation configurations and deformation mechanisms during processing of the alloy.

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