The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy

Aluminium castings offer significant weight reduction and improved fuel efficiency. Nowadays, aluminium recycling is widely practiced so impurity-related problems has become more important. Bismuth is one of the alloying elements added to aluminium alloys to improve their machinability, but little i...

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Main Author:	Ling, Tuong Thai
Format:	Thesis
Language:	English
Published:	2006
Subjects:	TJ Mechanical engineering and machinery
Online Access:	http://eprints.utm.my/id/eprint/5318/1/LingTuongThaiMFKM2006.pdf
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id	my-utm-ep.5318
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spelling	my-utm-ep.53182018-03-07T20:54:52Z The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy 2006-01 Ling, Tuong Thai TJ Mechanical engineering and machinery Aluminium castings offer significant weight reduction and improved fuel efficiency. Nowadays, aluminium recycling is widely practiced so impurity-related problems has become more important. Bismuth is one of the alloying elements added to aluminium alloys to improve their machinability, but little is known about its effect as a modifier or refiner. There has also been little investigation on the effect of low strontium contents (0.001wt% to 0.006wt%) on porosity formation. In the present work both sand and permanent moulds were used to produce bars containing varying strontium-bismuth ratios with some being treated with 0.2wt% antimony to investigate the interaction between these elements. A quench-during-solidification technique had been performed to study the effect of low strontium content on nucleation and growth of porosity in A356 alloy. Optical microscope, image analyzer, scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX) and x-ray diffraction (XRD) analysis were used to characterize the eutectic silicon, porosity and other phases. Strontium content as low as 0.004wt% was found to bring upon modification to the morphology of the eutectic silicon, whereas an addition of 0.005wt% bismuth refined the eutectic silicon. Beyond this level of bismuth the silicon phase was found to undergo coarsening. A strontium-bismuth ratio of at least 0.5 is suggested to be necessary to ensure a modified silicon morphology, whereas the refining effect of antimony was not affected by bismuth addition. Percentage area of porosity and pore roundness were found to increase with increasing strontium content, reasonably due to earlier pore growth and less shrinkage-type porosity in the castings. The nucleation of new pores occurred at the solid fraction of around 75%, regardless of strontium content. In the present work, the effect of low strontium content, cooling rate and heat treatment (T6) on the mechanical properties was also studied. The results showed that the mechanical properties were less affected by the strontium level but more by heat treatment and cooling rates. 2006-01 Thesis http://eprints.utm.my/id/eprint/5318/ http://eprints.utm.my/id/eprint/5318/1/LingTuongThaiMFKM2006.pdf application/pdf en public masters Universiti Teknologi Malaysia, Faculty of Mechanical Engineering Faculty of Mechanical Engineering
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	TJ Mechanical engineering and machinery
spellingShingle	TJ Mechanical engineering and machinery Ling, Tuong Thai The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy
description	Aluminium castings offer significant weight reduction and improved fuel efficiency. Nowadays, aluminium recycling is widely practiced so impurity-related problems has become more important. Bismuth is one of the alloying elements added to aluminium alloys to improve their machinability, but little is known about its effect as a modifier or refiner. There has also been little investigation on the effect of low strontium contents (0.001wt% to 0.006wt%) on porosity formation. In the present work both sand and permanent moulds were used to produce bars containing varying strontium-bismuth ratios with some being treated with 0.2wt% antimony to investigate the interaction between these elements. A quench-during-solidification technique had been performed to study the effect of low strontium content on nucleation and growth of porosity in A356 alloy. Optical microscope, image analyzer, scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX) and x-ray diffraction (XRD) analysis were used to characterize the eutectic silicon, porosity and other phases. Strontium content as low as 0.004wt% was found to bring upon modification to the morphology of the eutectic silicon, whereas an addition of 0.005wt% bismuth refined the eutectic silicon. Beyond this level of bismuth the silicon phase was found to undergo coarsening. A strontium-bismuth ratio of at least 0.5 is suggested to be necessary to ensure a modified silicon morphology, whereas the refining effect of antimony was not affected by bismuth addition. Percentage area of porosity and pore roundness were found to increase with increasing strontium content, reasonably due to earlier pore growth and less shrinkage-type porosity in the castings. The nucleation of new pores occurred at the solid fraction of around 75%, regardless of strontium content. In the present work, the effect of low strontium content, cooling rate and heat treatment (T6) on the mechanical properties was also studied. The results showed that the mechanical properties were less affected by the strontium level but more by heat treatment and cooling rates.
format	Thesis
qualification_level	Master's degree
author	Ling, Tuong Thai
author_facet	Ling, Tuong Thai
author_sort	Ling, Tuong Thai
title	The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy
title_short	The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy
title_full	The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy
title_fullStr	The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy
title_full_unstemmed	The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy
title_sort	effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of a356 aluminium casting alloy
granting_institution	Universiti Teknologi Malaysia, Faculty of Mechanical Engineering
granting_department	Faculty of Mechanical Engineering
publishDate	2006
url	http://eprints.utm.my/id/eprint/5318/1/LingTuongThaiMFKM2006.pdf
_version_	1747814578322931712

The effects of bismuth, strontium and antimony additions on the microstructure and mechanical properties of A356 aluminium casting alloy

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