scholarly journals Assessment of Mechanism of Pore Formation in Directionally Solidified A356 Alloy

2017 ◽  
Vol 17 (1) ◽  
pp. 157-162 ◽  
Author(s):  
M. Uludağ ◽  
D. Dişpinar
Keyword(s):  
Pore Formation ◽  
A356 Alloy ◽  
Test Sample ◽  
Directionally Solidified ◽  
Liquid Aluminium ◽  
Reduced Pressure ◽  
Pressure Test ◽  
Dissolved Hydrogen ◽  
Copper Chill ◽  
Cast Parts

Abstract It is well-known that the better the control of the liquid aluminium allows obtaining of better properties. One of the most important defects that is held responsible for lower properties has been the presence of porosity. Porosity has always been associated with the amount of dissolved hydrogen in the liquid. However, it was shown that hydrogen was not the major source but only a contributor the porosity. The most important defect that causes porosity is the presence of bifilms. These defects are surface entrained mainly due to turbulence and uncontrolled melt transfer. In this work, a cylindrical mould was designed (Ø30 x 300 mm) both from sand and die. Moulds were produced both from sand and die. Water cooled copper chill was placed at the bottom of the mould in order to generate a directional solidification. After the melt was prepared, prior to casting of the DC cast samples, reduced pressure test sample was taken to measure the melt quality (i.e. bifilm index). The cast parts were then sectioned into regions and longitudinal and transverse areas were investigated metallographically. Pore size, shape and distribution was measured by image analysis. The formation of porosity was evaluated by means of bifilm content, size and distribution in A356 alloy.

A Comparative Study of Porosity and Pore Morphology in a Directionally Solidified A356 Alloy

2009 ◽  
Vol 3 (1) ◽  
pp. 39-52 ◽  
Author(s):  
S. Akhtar ◽  
L. Arnberg ◽  
M. Di Sabatino ◽  
D. Dispinar ◽  
M. Syvertsen
Keyword(s):  
Comparative Study ◽  
A356 Alloy ◽  
Pore Morphology ◽  
Directionally Solidified

scholarly journals Effects of Casting Conditions for Reduced Pressure Test on Melt Quality of Al-Si Alloy

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1422
Author(s):  
Ho Sung Jang ◽  
Ho Jung Kang ◽  
Jin Young Park ◽  
Yoon Suk Choi ◽  
Sunmi Shin
Keyword(s):  
Sampling Method ◽  
Hydrogen Diffusion ◽  
Heating Temperature ◽  
Reduced Pressure ◽  
Hydrogen Diffusion Coefficient ◽  
Atmospheric Exposure ◽  
Pressure Test ◽  
The Difference ◽  
The One

The present study investigated the effect of the casting conditions for the reduced pressure test (RPT) on the melt quality of Al-Si alloy. The casting conditions considered in RPT were the atmospheric exposure during melting, sampling method, and mold pre-heating temperature. Density Index (DI) was measured to quantify the melt quality of the Al-Si alloy casted with the different casting conditions for the RPT. The sample with blocking atmospheric exposure during melting was 5.6% lower in DI than the one without blocking. DI showed a 1.9% gap between scooping-out and pouring sampling methods. Increasing mold pre-heating temperature from 100 °C to 250 °C increased the DI of the alloy from 8.5% to 18.7%. On the other hand, when the mold pre-heating temperature was 350 °C, the DI of the alloy dropped sharply to 0.9%. The melt quality of the alloys was analyzed by measuring the pores and microstructure and simulating the solidification of the samples. It was presumed that the oxides and inclusions in the molten alloys caused the difference in DI according to the atmospheric exposure and the sampling method. The difference in DI according to the mold pre-heating temperature could be understood by calculating the solidification starting time and hydrogen diffusion coefficient during the solidification of the alloys in RPT.

scholarly journals Mechanical Properties and Melt Quality Relationship of Sr-modified Al-12Si Alloy

2015 ◽  
Vol 15 (4) ◽  
pp. 134-140 ◽  
Author(s):  
M. Uludağa ◽  
M. Uyaner ◽  
F. Yilmaz ◽  
D. Dişpinar
Keyword(s):  
Mechanical Properties ◽  
Oxide Film ◽  
Tensile Testing ◽  
Porosity Formation ◽  
Reduced Pressure ◽  
Cast Part ◽  
Pressure Test ◽  
Relationship Of ◽  
Good Agreement

Abstract The formation of oxide film on the surface of aluminium melts, i.e. bifilms, are known to be detrimental when they are incorporated into the cast part. These defects causes premature fractures under stress, or aid porosity formation. In this work, Al-12 Si alloy was used to cast a step mould under two conditions: as-received and degassed. In addition, 10 ppi filters were used in the mould in order to prevent bifilm intrusion into the cast part. Reduced pressure test samples were collected for bifilm index measurements. Samples were machined into standard bars for tensile testing. It was found that there was a good agreement with the bifilm index and mechanical properties.

Effect of Sr addition on porosity formation in directionally solidified A356 alloy

2013 ◽  
Vol 26 (4) ◽  
pp. 201-208 ◽  
Author(s):  
H C Liao ◽  
W Song ◽  
Q G Wang ◽  
L Zhao ◽  
R Fan ◽  
...  
Keyword(s):  
A356 Alloy ◽  
Directionally Solidified ◽  
Porosity Formation

I-3 ASSESSMENT OF REDUCED PRESSURE TEST FOR HYDORGEN MEASUREMENT OF ALUMINUM CASTING(Session: Casting/Molding)

2006 ◽  
Vol 2006 (0) ◽  
pp. 149
Author(s):  
R. Sirichaivetkul ◽  
A. Rengsomboon ◽  
W. Samit ◽  
N. Moonrin ◽  
S. Petcrie ◽  
...  
Keyword(s):  
Aluminum Casting ◽  
Reduced Pressure ◽  
Pressure Test

The Design of Screw-Drive Mechanism for Testing Device

2012 ◽  
Vol 271-272 ◽  
pp. 1206-1210
Author(s):  
Ying Jie Tan ◽  
Chang Ming Zhang
Keyword(s):  
Test Sample ◽  
Testing Device ◽  
Test Device ◽  
Main Structure ◽  
Drive Mechanism ◽  
Screw Drive ◽  
Actual Production ◽  
Pressure Test

The main structure of bearing frame for pressure test device and it’s functions are described in this paper. For the pressure test device with float collar and float shoe, the screw transmits movement with standing pressuring load. According to the needs of actual production and the requirements of test sample pressuring, this paper designed a drive mechanism for screw rod, calculated the stress and checked the correlated stiffness. The result shows that it is reasonable, safe and reliable for screw-drive mechanism, depending on the operation behavior of float collar and float shoe pressure test device.

Effect of Melt Quality and Quenching Temperature on the Mechanical Properties of SIMA 2024 and 7075

2012 ◽  
Vol 445 ◽  
pp. 171-176
Author(s):  
Engin Tan ◽  
Ali Riza Tarakcilar ◽  
Derya Dispinar
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Mechanical Tests ◽  
Fatigue Tests ◽  
Grain Structure ◽  
Quenching Temperature ◽  
Reduced Pressure ◽  
Pressure Test ◽  
Sima Process ◽  
Spherical Grains

Spherical grains can be obtained by several semisolid processes in aluminium alloys. One of these methods is called Strain Induced Melt Activated (SIMA). In this work, commercially available 2024 and 7075 alloys were subjected SIMA process. First, optimised process parameters were investigated for the homogeneous spherical grain structure. This was followed by solution heat treatment of the parts. For the quenching medium, room temperature and 80°C boiling water was selected. The effect of different quenching temperatures over the mechanical properties was tested. Hardness, tensile and fatigue tests were applied. In addition, reduced pressure test was used to assess alloy quality and the results were compared with the mechanical tests.

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