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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.49  No.4 (2008)  >  pp.737-745

MATERIALS TRANSACTIONS
<<Previous article Vol.49  No.4 (2008)   pp.737 - 745 Next article>>

Tensile Properties of Forged Direct-Squeeze-Cast Al-(6.0∼8.0 mass%)Si-(0.3∼0.52 mass%)Mg Alloy

Teng-Shih Shih1), Po-Chen Chen1) and Wei-Shian Tsai1)
1) National Central University, Department of Mechanical Engineering Chung-Li

The effects of lubricants on the quality of squeeze-cast Al-(6.0∼8.0 mass%)Si-(0.3∼0.52 mass%)Mg alloys were studied. Different melts with varying amounts of Si and Mg were prepared and then directly squeeze-cast into cakes. Different lubricants and two different pressures, 60 and 120 MPa, were used in the production of the cakes. These squeeze-cast cakes were then forged and heat-treated. Tensile specimens prepared from the forged and heat-treated cakes were tested to determine their tensile properties. Among all the variables tested, the Weibull modulus (in ultimate tensile strength, UTS) was the largest (m=53.7) for the cakes squeeze-cast at 120 MPa using water-based BN powder (∼4 μm in size) as a lubricant. After polishing and ultrasonic-vibration treatment, oxide films appeared as foggy films on the chilled blocks and forged cakes. Reaction films were also observed on the tensile fracture surfaces of the tested bars. They were particularly apparent on the bars produced from cakes that had been prepared using an oil-based lubricant. The area ratios of the foggy films and reaction films on the samples were calculated. The Weibull modulus (in UTS) of the forged cakes after T6 treatment was significantly affected by both the pore count and the total area ratio covered by reaction films and foggy films.


Keyword:
A356 alloy, direct squeeze-casting, pore counts, foggy films

Received: June 22, 2007
Accepted: January 10, 2008 , Published online: March 25, 2008
Copyright (c) 2008 The Japan Institute of Metals

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