EFFECT OF IRON CONTENT ON THE FORMATION INTERMETALLIC Al-Fe-Si PHASES, FLUIDITY, POROSITY, AND HARDNESS IN ALUMINIUM ALLOY ̉̉ SILICON
Approximately 85-90% of total components made of cast aluminum alloys are alloys of Al - Si. While it rejected due to porosity in Al-Si casting industries that uses gravity casting method is almost as high as 60%. Formation of shrinkage porosity is closely related to the presence of iron element in...
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Format: | Theses |
Language: | Indonesia |
Online Access: | https://digilib.itb.ac.id/gdl/view/20396 |
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Institution: | Institut Teknologi Bandung |
Language: | Indonesia |
Summary: | Approximately 85-90% of total components made of cast aluminum alloys are alloys of Al - Si. While it rejected due to porosity in Al-Si casting industries that uses gravity casting method is almost as high as 60%. Formation of shrinkage porosity is closely related to the presence of iron element in these alloys. <br />
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Preparation of alloy Al - (7.6 to 8%) Si which has a Fe content varies from 0.127% to 1.43% is used to determine the effect of iron in Al-Si alloys. Melting alloy was carried out in a muffle furnace and then poured into two types of mold. Sand mold to determine the fluidity and metal molds to determine the cooling rate. <br />
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Preparation of alloy Al - (7.6 to 8%) Si by selecting the losing value to the element Si = 2% and Fe = 1% in the calculation of material balance, giving the chemical composition of alloys close to the test results spectrometer so that it can be said that the chemical composition of specimens in accordance with planned. <br />
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The researching results showed that increasing the iron content in the alloy from 0.127% to 1.43% cause local cooling rate more slowly so that the dendrite arm spacing (DAS) enlarged. The higher content of iron also causes an increase in the maximum length of β-phase intermetallic (Al5FeSi) from 63.49 μm to 261.3 μm, the fraction of Fe-intermetallic from 1.8% to 7.95%, and hardness of alloys from 53.66 BHN to 73 , 7 BHN, but the fluidity of alloy decreased from 96.5 cm to 70.5 cm. <br />
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Examination using EDS showed that the β-phase has a composition of atomic fraction Al0,77Fe0,105Mn0,0023Si0,123. Platelet phase of growth has become more extreme when the iron content in alloys Al - (7.6 to 8%) Si is greater than 0.529%. This causes the amount of porosity in the alloy increases with increasing amount of β-phase. <br />
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The decrease in porosity occurs when the iron content increases up to 0.529%. The value of Fe = 0.529% Fe approaching the critical value for these alloys 0.535%) which will cause a maximum permeability≈(Fe critical interdendritik network. The decrease in porosity caused by the decrease of tortuosity factor causes a change in growth patterns of silicon network. So, on the condition of critical Fe alloy the amount of porosity would be minimum. |
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