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

2008 ◽

Vol 141-143 ◽

pp. 409-414 ◽

Cited By ~ 6

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.

Download Full-text

The influences of the microstructure morphology of A356 alloy on its rheological behavior in the semi-solid state

Science and Technology of Advanced Materials ◽

10.1016/s1468-6996(01)00053-5 ◽

2001 ◽

Vol 2 (1) ◽

pp. 219-223 ◽

Cited By ~ 8

Author(s):

Yuefeng Zhu ◽

Jinglin Tang ◽

Yizhi Xiong ◽

Zhenning Wu ◽

Chen Wang ◽

...

Keyword(s):

Solid State ◽

Rheological Behavior ◽

A356 Alloy ◽

Microstructure Morphology ◽

Semi Solid

Download Full-text

Influence of Morphology on the Rheological Behavior of Semi-Solid A356 Aluminum Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.116-117.601 ◽

2006 ◽

Vol 116-117 ◽

pp. 601-605

Author(s):

Heng Hua Zhang ◽

Xian Nian Zhang ◽

Guang Jie Shao ◽

Luo Ping Xu ◽

Yi Tao Yang ◽

...

Keyword(s):

Aluminum Alloy ◽

Solid State ◽

Rheological Behavior ◽

Apparent Viscosity ◽

Flow Behavior ◽

A356 Alloy ◽

Solid Alloy ◽

A356 Aluminum Alloy ◽

A356 Aluminum ◽

Semi Solid

The morphology of semi-solid alloy is one of the key influence factors on the rheological behavior of slurry during die filling and the mechanical properties of formed parts. However, it is difficult to study such effect due to hard controlling of morphology in semi-solid state. In this paper, a self-developed Searle-type viscometer was used to determine the rheological behavior of A356 aluminum alloy in different morphology, which was refined with the salts mixture of K2TiF6 and KBF4. The results indicated that the flow behavior of refined A356 alloy in the semi-solid state possesses obviously thixotropic behavior under isothermal shearing condition with less time to reach steady state and lower steady apparent viscosity as compared to that of the A356 alloy. During continuous cooling at a constant shearing rate, the apparent viscosity of refined A356 slurry in the same solid fraction decreased with the content of Ti. It is shown from quantitative image analysis that the primary α-Al grain in the refined alloy evolves from dendrites to rosettes or sphericitys, and then tends to be rounder and finer in higher Ti content. The mechanism of the influence of morphology on rheological behavior was also discussed in this paper.

Download Full-text