scholarly journals Effect of Stirring Speed and Flow Pattern on the Microstructure of a Rheocast Al-Mg Alloy

10.30544/131 ◽  
2015 ◽  
Vol 21 (1) ◽  
pp. 35-44
Author(s):  
P. Melali ◽  
P. Ashtijoo ◽  
B. Niroumand
Keyword(s):  
Flow Pattern ◽  
Microstructure Evolution ◽  
The Other ◽  
Mg Alloy ◽  
Crucible Wall ◽  
Primary Particles ◽  
Semi Solid

The effect of stirring speed and the flow pattern inside a processing crucible were examined in this study. This investigation was performed on the microstructure of mechanically stirred Al–8% Mg. Results reveal that by increasing the stirring speed, morphology of primary particles becomes finer and more spherical. By using baffles, the flow pattern inside the crucible changes. This change causes the melt to accelerate along the crucible wall and producing the finer structure, more spherical and nondendritic. the model, named as nucleation and separation from the wall, posses the ability to explain the microstructure evolution in semi solid fabricated slurry. It must be mentioned that the other model named “fragmentation-agglomeration’’ cannot explain the changes in microstructure by using baffles.

Role of Iron-Rich Phases and Porosity on the Ductility of Rheocast Al-Mg-Si-Alloys

2022 ◽  
Vol 327 ◽  
pp. 65-70
Author(s):  
Qing Zhang ◽  
Stefan Jonsson ◽  
Arne K. Dahle ◽  
Anders E.W. Jarfors
Keyword(s):  
Quantitative Analysis ◽  
Tensile Tests ◽  
Intermetallic Phases ◽  
The Other ◽  
Homogeneous Microstructure ◽  
Fracture Surfaces ◽  
Other Hand ◽  
Primary Particles ◽  
Semi Solid

Treatment of the slurry is important during RheoMetalTM casting. In this work, semi-solid slurries were prepared under different stirring intensities, using two types of stirrers: a naked rod (for regular stirring) and a rod with two blades (for intensified stir). Tensile tests were performed, investigating fracture surfaces, as well as metallographic samples. The results show that intensified stir produces castings with finer primary particles and a more homogeneous microstructure. On the other hand, more faceted Fe-rich phases are found along the α-Al grains boundary as well, due to the dissolution of Fe from the stirrers. Moreover, for intensified stir castings, the porosity found on the fracture surfaces are smaller, while more brittle eutectic phases and second (intermetallic) phases, especially Fe-rich phases, are observed. Consequently, the castings with intensified stir show worse ductility. Finally, a quantitative analysis was made regarding ductility, affected both by porosity and the presence of Fe-rich phases.

Microstructure Evolution of Deformed Magnesium Alloy in Semi-Solid State

2005 ◽  
Vol 488-489 ◽  
pp. 313-316
Author(s):  
Sen Yuan ◽  
Wu Xiao Wang ◽  
Bai Ling Jiang
Keyword(s):  
Solid State ◽  
Magnesium Alloy ◽  
Microstructure Evolution ◽  
High Energy ◽  
Mg Alloy ◽  
Continuous Heating ◽  
Heating Process ◽  
Semisolid State ◽  
Semi Solid ◽  
Temperature Time

Magnesium alloy slurry was prepared using Strain-Induced Melt Activation(SIMA) technique. The samples were quenched into water so as to fix the high temperature instantaneous microstructures. The microstructure evolution of compressed deformation Mg alloy is studied in the process of continuous heating and iso-temperature of semi-solid state. The results indicate that deformed Mg alloy (AZ91) has first occurred to have the conversion of dendrite crystal-oriented isometric crystals in the continuous heating process. When the temperature rises to the range of semisolid state, the region with high energy at the pressed stripes begins to melt, showing that the cellular structures emerge in the crystal boundary and melting micro-pool phenomena appear within the crystals. With the iso-temperature time in semisolid state prolongs, the isometric crystals can be gradually converted into spherical crystal grains.

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.

scholarly journals Selective Cytotoxicity of Carboxypeptidase-activated Methotrexate ex-Peptides

Pteridines ◽  
1989 ◽  
Vol 1 (1) ◽  
pp. 65-69 ◽  
Author(s):  
Karin S. Vitols ◽  
Yolanda D. Montejano ◽  
Ulrike Kuefner ◽  
F. M. Huennekens
Keyword(s):  
Monoclonal Antibodies ◽  
Amino Acid ◽  
Suspension Culture ◽  
Parent Drug ◽  
Model System ◽  
The Other ◽  
Carboxypeptidase A ◽  
Selective Cytotoxicity ◽  
Cell Kill ◽  
Semi Solid

Summary Methotrexate ex-pep tides (derivatives in which an amino acid is linked covalently to the ex-carboxyl of the glutamate residue on the parent drug) can be hydrolyzed by specific carboxypeptidases to yield free Methotrexate (MTX) and the corresponding amino acid. Studies with L12l0 cells in suspension culture have shown that the MTX pep tides can serve as "pro-drugs": Because of their inability to be taken up by cells, they are relatively non-toxic. When co-administered with appropriate carboxypeptidases, however, they become equitoxic with MTX. In the present investigation, the potential of the MTX-ala/carboxypeptidase A combination for providing regional cytotoxicity was demonstrated in a model system involving L12l0 cells propagated in semi-solid agarose. When cells and one of the components (MTX peptide or carboxypeptidase) were distributed uniformly throughout the agarose, and the other component was immobilized at the center, a discrete zone of cell kill radiated from the fixed component. These results suggest the possibility of developing a new mode of cancer chemotherapy involving circulating MTX peptides in conjunction with carboxypeptidases linked covalently to tumor-targeted monoclonal antibodies.

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