Rheological Behavior of Semi-Solid Slurry of A356 Alloy at High Shear and Cooling Rates

2008 ◽  
Vol 141-143 ◽  
pp. 409-414 ◽  
Author(s):  
N. Barman ◽  
P. Dutta
Keyword(s):  
Shear Rate ◽  
Cooling Rate ◽  
Solid Fraction ◽  
Rheological Behavior ◽  
Outer Cylinder ◽  
A356 Alloy ◽  
High Shear ◽  
Concentric Cylinder ◽  
Cooling Rates ◽  
Series Of Experiments

The rheological behavior of semisolid aluminium alloy (A356) slurry is investigated by using a concentric cylinder viscometer under high cooling rate (30 to 50°C/min) and high shear rate (650 to 1500s-1) conditions. Two different series of experiments are carried out. In all of these experiments, the pellets of A356 alloy are poured into the outer cylinder where they melt completely by resistance heating. When the inner cylinder is placed concentrically, the molten metal resides in the annular space between the cylinders. As the inner cylinder rotates, the alloy is sheared continuously during cooling from a temperature of 630°C, and a slurry forms. In the first series of experiments, for different cooling rates, shearing continues under a constant shear rate until rotation of the inner cylinder stops. During experiments, the temperature of the slurry is measured continuously using a K-type thermocouple, from which the solid fraction is calculated. In the second series of experiments, the molten alloy is cooled and sheared continuously at different shear rates for a given cooling rate. The apparent viscosity of the slurry is calculated by measuring the torque applied to the inner cylinder and its rotational speed. The results show that the slurry viscosity increases with increasing fraction of solid and increasing cooling rate, and it decreases with increasing shear rate. At high values of shear and cooling rates, the viscosity varies gradually up to a solid fraction of about 0.5.

The Rheological Behavior of HS6-5-2 Tool Steel for Non-Isothermal Processing

2012 ◽  
Vol 192-193 ◽  
pp. 317-322
Author(s):  
Farzad Hosseini Yekta ◽  
S.A. Sadough ◽  
Vahid Pouyafar ◽  
Amin Jabbari
Keyword(s):  
Shear Rate ◽  
Cooling Rate ◽  
Tool Steel ◽  
Solid Fraction ◽  
Rheological Behavior ◽  
Liquid Fraction ◽  
Outer Cylinder ◽  
Processing Temperature ◽  
Applied Torque ◽  
Semi Solid

The rheological behavior of semi-solid tool steel is investigated using a conventional rheometer under cooling rate and shear rate. The processing of steels in semi-solid state is still at development stage due to the high processing temperature involved. The candidate grades of steel for thixoforming are high speed, high carbon, stainless steel and ductile iron. TheHS6-5-2 tool steel has a wide semi-solid range of over 200 C and the required spheroidal microstructure achieved by partial re-melting from as supplied state without any mechanical agitation, indicated the potential of this grade to be investigated in semi-solid processing. For non-isothermal processing an increase of solid fraction related to solidification due to thermal exchanges is observed. In the first series of experiment after melting the feed stock in an alumina cup, the alloy is sheared continuously by a rotating rod with a constant shear rate under three different cooling rates to the 55% corresponding liquid fraction. In the second series of experiment three different shear rates were applied under a constant cooling rate. The apparent viscosity of the slurry as a function of cooling rate and solid fraction is calculated from the applied torque to the outer cylinder. The results show that the slurry viscosity decreases with increasing shear rate and increases with increasing cooling rate and solid fraction. Additionally for a given solid fraction, shear thinning behavior is observed.

Rheological behavior of SAN/PC blends under extremely high shear rate

1989 ◽  
Vol 37 (7) ◽  
pp. 1837-1853 ◽  
Author(s):  
Hideroh Takahashi ◽  
Takaaki Matsuoka ◽  
Takashi Ohta ◽  
Kenzo Fukumori ◽  
Toshio Kurauchi ◽  
...  
Keyword(s):  
Shear Rate ◽  
Rheological Behavior ◽  
High Shear Rate ◽  
High Shear

Rheological Behavior of Various Al Alloys during Solidification

2012 ◽  
Vol 710 ◽  
pp. 35-42
Author(s):  
Michel Suéry
Keyword(s):  
Ductile Fracture ◽  
Cooling Rate ◽  
Solid Fraction ◽  
Rheological Behavior ◽  
Liquid Films ◽  
Al Alloys ◽  
Tensile Behavior ◽  
Controlled Cooling ◽  
Sharp Transition ◽  
Solid Specimen

This paper is concerned with the tensile behavior of various Al alloys during solidification obtained by using an initially solid specimen heated locally until it becomes fully liquid and then partially solidified at a controlled cooling rate. It is shown that for Al-Cu as well as for Al-Si-Mg alloys, a similar behavior is observed with a sharp transition on the stress-solid fraction curve when the coalescence solid fraction of the dendrites is reached. Below the transition fracture occurs along liquid films for very low stresses whereas beyond this transition, ductile fracture is observed leading to higher stresses.

scholarly journals Statistical Relationship Between Strontium Content and Cooling Rate on A356 Alloy by Using Regression Analysis

2021 ◽  
pp. 31-37
Author(s):  
Batuhan Dogdu ◽  
Onur Ertugrul
Keyword(s):  
Cooling Rate ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Chemical Modifier ◽  
Statistical Relationship ◽  
Silicon Phase ◽  
Strontium Content ◽  
Cooling Rates ◽  
Cast Part ◽  
Eutectic Modification

Eutectic silicon modification is an important casting parameter on Al-Si alloys on the aspect of mechanical capability and energy absorption of the cast part. Chemical modifier element strontium has been used to obtain eutectic modification on Al-Si alloy commercially. On the other hand, high cooling rate on Al-Si alloys both refine dendrites and silicon phase which enhances mechanical characteristic. In order to find a statistical relationship between strontium amount and cooling rate, a special mold was designed in order to obtain different range of cooling rates in same cast part, then tensile test data of A356 alloy were analyzed in Minitab software. Therefore, after regression and analysis of variance tests have been proceeded, it was found that strontium amount is only dominant for lower cooling rates of < 0.9 oC.

scholarly journals Rheological Behavior of the Composites of Carboxymethylcellulose-Zinc Oxide/Starch

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Marcio Da Silva Coutinho ◽  
Danielle Cristina Fernandes Da Silva ◽  
Gustavo Ribeiro Xavier ◽  
Norma Gouvêa Rumjanek ◽  
Paulo Jansen De Oliveira
Keyword(s):  
Zinc Oxide ◽  
Shear Rate ◽  
Rheological Behavior ◽  
Arrhenius Equation ◽  
Flow Behavior ◽  
High Shear ◽  
Recovery Test ◽  
Creep And Recovery ◽  
Rate Testing ◽  
Starch Blends

The rheological behavior of the carboxymethylcellulose (CMC) / starch blends with and without zinc oxide (ZnO) have been investigated by controlled shear rate testing ramps. All blends showed high shear thinning flow behavior, (n=0,10 - 0,32) without ZnO and (n=0,10-0,29) with ZnO. The consistency index (K) and apparent viscosity (ηa,100 ) decreased with increasing amount of starch and with the addition of 1% wt ZnO. The results also showed that occurs an inversion in the elastic and viscous modulii behavior between 25 and 700C, obeying the Arrhenius equation. The study of activation energy showed that ZnO acts in the CMC phase, increase of viscosity of mixtures. The creep and recovery test indicated a decrease in the viscosity zero shear rate, indicating an increase of viscous character.  The phase angle results also confirm an increase of viscosity with addition of ZnO.

scholarly journals Revisiting the 1954 suspension experiments of R. A. Bagnold

2002 ◽  
Vol 452 ◽  
pp. 1-24 ◽  
Author(s):  
M. L. HUNT ◽  
R. ZENIT ◽  
C. S. CAMPBELL ◽  
C. E. BRENNEN
Keyword(s):  
Shear Rate ◽  
Outer Cylinder ◽  
Fluid Viscosity ◽  
Concentric Cylinder ◽  
Stress Measurements ◽  
Solid Mixture ◽  
Normal Forces ◽  
Solids Concentration ◽  
Wide Range ◽  
Experimental Findings

In 1954 R. A. Bagnold published his seminal findings on the rheological properties of a liquid–solid suspension. Although this work has been cited extensively over the last fifty years, there has not been a critical review of the experiments. The purpose of this study is to examine the work and to suggest an alternative reason for the experimental findings. The concentric cylinder rheometer was designed to measure simultaneously the shear and normal forces for a wide range of solid concentrations, fluid viscosities and shear rates. As presented by Bagnold, the analysis and experiments demonstrated that the shear and normal forces depended linearly on the shear rate in the ‘macro-viscous’ regime; as the grain-to-grain interactions increased in the ‘grain-inertia’ regime, the stresses depended on the square of the shear rate and were independent of the fluid viscosity. These results, however, appear to be dictated by the design of the experimental facility. In Bagnold’s experiments, the height (h) of the rheometer was relatively short compared to the spacing (t) between the rotating outer and stationary inner cylinder (h/t = 4.6). Since the top and bottom end plates rotated with the outer cylinder, the flow contained two axisymmetric counter-rotating cells in which flow moved outward along the end plates and inward through the central region of the annulus. At higher Reynolds numbers, these cells contributed significantly to the measured torque, as demonstrated by comparing Bagnold's pure-fluid measurements with studies on laminar-to-turbulent transitions that pre-date the 1954 study. By accounting for the torque along the end walls, Bagnold’s shear stress measurements can be estimated by modelling the liquid–solid mixture as a Newtonian fluid with a corrected viscosity that depends on the solids concentration. An analysis of the normal stress measurements was problematic because the gross measurements were not reported and could not be obtained.

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