scholarly journals How Slight Solidification Rate Variations within Cast Plate Affect Mechanical Response: A Study on As-Cast A356 Alloy with Cu Additions

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Maria Teresa Di Giovanni ◽  
Emanuela Cerri ◽  
Takeshi Saito ◽  
Shahid Akhtar ◽  
Petter Åsholt ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Eutectic Silicon ◽  
Solidification Rate ◽  
Particle Surface ◽  
A356 Alloy ◽  
Equivalent Diameter ◽  
Particle Surface Area ◽  
Eutectic Si ◽  
Backscattered Electron ◽  
Cast Plate

The present work investigates a narrow range of secondary dendrite arm spacing (SDAS), in an as-cast A356 alloy with and without copper (Cu) additions. Cu was added to the base A356 alloy melt to reach the target concentration of 0.5 and 1 wt.%. Samples were selected from 3 different positions within the cast plate, offering 30, 35, and 40 μm SDAS variants. Tensile curves revealed a strong influence between the specimen cutting position and strength, with a pronounced effect in the Cu-containing alloys. Hardness measurements did not confirm the tensile response; hence, to understand the phenomenon, microstructural features have been investigated in detail. Eutectic silicon (Si) particle equivalent diameter (ED) size decreased from the top (T) to the bottom (B) position of the cast. Eutectic Si particle surface area (A%) was found to be denser at the B as compared to the T and simultaneously in the Cu-containing alloy as compared to the Cu-free reference alloy. Backscattered electron (BSE) images were employed to investigate the nature of the Cu-rich intermetallic phases. In conclusion, electrical conductivity measurements were performed to confirm the trends observed.

Mechanical Properties and Fracture Behavior of Indirect Squeeze-Cast A354 Alloy Using Local Pressurization

2016 ◽  
Vol 850 ◽  
pp. 502-510
Author(s):  
Hai Jun Liu ◽  
Lie Jun Li ◽  
Jian Wei Niu ◽  
Ji Xiang Gao ◽  
Xue Wen Chen
Keyword(s):  
Mechanical Properties ◽  
Tensile Properties ◽  
Fracture Behavior ◽  
Eutectic Silicon ◽  
Solidification Rate ◽  
Fracture Morphology ◽  
Shrinkage Cavity ◽  
Squeeze Cast ◽  
Ductile Mode ◽  
Eutectic Si

The effect of local pressurization on mechanical properties and fracture behavior of indirect squeeze-cast A354 alloy has been investigated. As compared to conventional process, the porosity and shrinkage cavity for heavy sectioned squeeze castings were improved by the indirect squeeze casting, while its tensile properties were inferior to other parts of the casting. That is mainly due to that inhomogeneous eutectic Si particles within strip, angular and fragment shapes distribute in bulky α-Al cells, which is caused by slower solidification rate. After T6 treatment, the fragmentation and spheroidization of the eutectic silicon happened. Under this situation, the effect of fragmentation on α-Al matrix reduced. Tensile properties of the casting (both local pressurization part and non-local pressurization part) were enhanced greatly, by 36.8% and 25.4%, respectively. Fracture analysis results show that the type of fracture morphology is changed from mixed mode of brittle cleavage and ductile to ductile mode after T6-treatment.

The Effect of a Rotating Magnetic Field on the Solidification of A356 Alloy Modified by Strontium

2008 ◽  
Vol 589 ◽  
pp. 305-310 ◽  
Author(s):  
Gréta Gergely ◽  
Zoltán Gácsi ◽  
Olivér Bánhidi ◽  
Jenő Kovács ◽  
Arnold Rónaföldi
Keyword(s):  
Magnetic Field ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Rotating Magnetic Field ◽  
Strontium Content ◽  
Investigation Methods ◽  
Magnetic Stirring ◽  
Eutectic Si

The A356 alloy, which consists of 100-200 ppm modifier, namely strontium was examined. The samples were solidified unidirectionally, and each sample had a pair which was solidified in a rotating magnetic field. The microstructure of the samples: morphology and the fraction of eutectic silicon was studied. The morphology of eutectic Si was very different in the samples - the samples solidified at different movement velocities – so it was necessary to determine the quantity of strontium. Magnetic stirring changes both the strontium content and the extent of modification. This paper describes the investigation methods and the effects of strontium modification.

HORIZONS FOR DESIGN OF FILLED RUBBER INFORMED BY MOLECULAR DYNAMICS SIMULATION

2017 ◽  
Vol 90 (2) ◽  
pp. 238-263 ◽  
Author(s):  
Scott M. Smith ◽  
David S. Simmons
Keyword(s):  
Molecular Dynamics ◽  
Granular Media ◽  
Mechanical Response ◽  
Particle Surface ◽  
Dynamics Simulation ◽  
Particle Surface Area ◽  
Mechanical Reinforcement ◽  
Microscopic Mechanism ◽  
Filler Structure ◽  
Rubber Filler

ABSTRACT Fillers such as carbon black provide a long-standing and essential strategy for the mechanical reinforcement of rubber in tires and other load-bearing applications. Despite their technological importance, however, the microscopic mechanism of this reinforcement remains a matter of considerable debate. A predictive understanding of filler-based reinforcement could catalyze the design of new rubber-filler composites with enhanced performance. Molecular dynamics simulations of rubber mechanical response in the presence of structured fillers offer a new strategy for resolving the origins of filler-based reinforcement and guiding filler design. Results of for ideal rubber-filler dispersions over a range of filler structures suggest that neither hydrodynamic effects nor non-deformable “bound rubber domains” are necessary to achieve high reinforcement. Moreover, simulations show that particle surface area is a poor predictor of reinforcement. Instead, simulated reinforcement correlates strongly with filler structure, with more rarified filler structure predicting much greater reinforcement at fixed loading. Simulation results are consistent with a scenario in which reinforcement at industrially relevant loadings is dominated by formation of a jammed network of filler particles, suggesting that reinforced rubber can be understood as a superposition of two materials: a rubbery solid, and a jammed granular solid. This perspective points to an opportunity to improve filler-reinforced rubber design by leveraging concepts and expertise developed over many decades in the fields of jamming and granular media.

scholarly journals Effect of Solidification Rate and Rare Earth Metal Addition on the Microstructural Characteristics and Porosity Formation in A356 Alloy

2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
M. G. Mahmoud ◽  
A. M. Samuel ◽  
H. W. Doty ◽  
S. Valtierra ◽  
F. H. Samuel
Keyword(s):  
Rare Earth ◽  
Solidification Rate ◽  
A356 Alloy ◽  
Earth Metal ◽  
Atomic Radius ◽  
Shrinkage Porosity ◽  
Minor Effect ◽  
Porosity Formation ◽  
Agent Interaction ◽  
Eutectic Si

The present study was performed on A356 alloy with the main aim of investigating the effects of La and Ce additions to 356 alloys (with and without 100 ppm Sr) on the microstructure and porosity formation in these alloys. Measured amounts of La, Ce, and Sr were added to the molten alloy. The results showed that, in the absence of Sr, addition of La and Ce leads to an increase in the nucleation temperature of the α-Al dendritic network with a decrease in the temperature of the eutectic Si precipitation, resulting in increasing the freezing range. Addition of 100 ppm Sr results in neutralizing these effects. The presence of La or Ce in the casting has a minor effect on eutectic Si modification, in spite of the observed depression in the eutectic temperature. It should be noted that Ce is more effective than La as an alternate modifying agent. According to the atomic radius ratio, rLa/rSi is 1.604 and rCe/rSi is 1.559, theoretically, which shows that Ce is relatively more effective than La. The present findings confirm that Sr is the most dominating modification agent. Interaction between rare earth (RE) metals and Sr would reduce the effectiveness of Sr. Although modification with Sr causes the formation of shrinkage porosity, it also reacts with RE-rich intermetallics, resulting in their fragmentation.

Quantities Directly Measurable by Scattering

2018 ◽  
Author(s):  
Eaton E. Lattman ◽  
Thomas D. Grant ◽  
Edward H. Snell
Keyword(s):  
Molecular Weight ◽  
Particle Shape ◽  
Particle Surface ◽  
Scattering Data ◽  
Radius Of Gyration ◽  
Particle Volume ◽  
Particle Surface Area ◽  
Scattering Angle ◽  
Particle Dimension ◽  
Maximum Particle

In this chapter we note that solution scattering data can be divided into four regions. At zero scattering angle, the scattering provides information on molecular weight of the particle in solution. Beyond that, the scattering is influenced by the radius of gyration. As the scattering angle increases, the scattering is influenced by the particle shape, and finally by the interface with the particle and the solution. There are a number of important invariants that can be calculated directly from the data including molecular mass, radius of gyration, Porod invariant, particle volume, maximum particle dimension, particle surface area, correlation length, and volume of correlation. The meaning of these is described in turn along with their mathematical derivations.

Influence of particle surface area on the toxicity of insoluble manganese dioxide dusts

1997 ◽  
Vol 71 (12) ◽  
pp. 725-729 ◽  
Author(s):  
Dominique Lison ◽  
Cécile Lardot ◽  
François Huaux ◽  
Giovanna Zanetti ◽  
Bice Fubini
Keyword(s):  
Manganese Dioxide ◽  
Surface Area ◽  
Particle Surface ◽  
Particle Surface Area

scholarly journals Ice nucleation abilities of soot particles determined with the Horizontal Ice Nucleation Chamber

2018 ◽  
Vol 18 (18) ◽  
pp. 13363-13392 ◽  
Author(s):  
Fabian Mahrt ◽  
Claudia Marcolli ◽  
Robert O. David ◽  
Philippe Grönquist ◽  
Eszter J. Barthazy Meier ◽  
...  
Keyword(s):  
Particle Size ◽  
Water Saturation ◽  
Particle Surface ◽  
Water Vapor Sorption ◽  
Contact Angles ◽  
Ice Nucleation ◽  
Particle Surface Area ◽  
Soot Particles ◽  
Microphysical Properties ◽  
Homogeneous Freezing

Abstract. Ice nucleation by different types of soot particles is systematically investigated over the temperature range from 218 to 253 K relevant for both mixed-phase (MPCs) and cirrus clouds. Soot types were selected to represent a range of physicochemical properties associated with combustion particles. Their ice nucleation ability was determined as a function of particle size using relative humidity (RH) scans in the Horizontal Ice Nucleation Chamber (HINC). We complement our ice nucleation results by a suite of particle characterization measurements, including determination of particle surface area, fractal dimension, temperature-dependent mass loss (ML), water vapor sorption and inferred porosity measurements. Independent of particle size, all soot types reveal absence of ice nucleation below and at water saturation in the MPC regime (T>235 K). In the cirrus regime (T≤235 K), soot types show different freezing behavior depending on particle size and soot type, but the freezing is closely linked to the soot particle properties. Specifically, our results suggest that if soot aggregates contain mesopores (pore diameters of 2–50 nm) and have sufficiently low water–soot contact angles, they show ice nucleation activity and can contribute to ice formation in the cirrus regime at RH well below homogeneous freezing of solution droplets. We attribute the observed ice nucleation to a pore condensation and freezing (PCF) mechanism. Nevertheless, soot particles without cavities of the right size and/or too-high contact angles nucleate ice only at or well above the RH required for homogeneous freezing conditions of solution droplets. Thus, our results imply that soot particles able to nucleate ice via PCF could impact the microphysical properties of ice clouds.

The Effect of Electromagnetic Vibration on the Structure Control of A356 Alloy

2007 ◽  
Vol 539-543 ◽  
pp. 329-332 ◽  
Author(s):  
Jung Pyung Choi ◽  
Tae Woon Nam ◽  
Eui Pak Yoon
Keyword(s):  
Structural Control ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Low Frequency ◽  
Primary Aluminum ◽  
Magnetic Flux Density ◽  
Structure Control ◽  
Electromagnetic Vibration ◽  
Fine Fiber ◽  
Electro Magnetic

The structural control of A356 alloy, which was not studied among various electromagnetic processing of materials, was considered applying the alternating current and direct current magnetic flux density. The main aim of the present study is to investigate the effects of electromagnetic vibration on the macro and microstructure of A356 alloy in order to develop a new process of structural control in A356 alloy. When the electromagnetic vibration is conducted for changing the shape of primary aluminum, at low frequency (≤60Hz), the shape of dendrite is changed speroidal shape. When the electromagnetic vibration is conducted for changing the shape of eutectic silicon, a morphological change of the eutectic silicon from coarse platelet flakes to fine fiber shape is observed with EMV (Electro Magnetic Vibration) process at high frequency (≥500Hz).

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