Bulletin of Materials Science

, Volume 34, Issue 6, pp 1223–1231 | Cite as

Poisoning effect of bismuth on modification behaviour of strontium in LM25 alloy

Article

Abstract

Nucleation and growth, temperature measurements and microstructure observations of silicon phase are presented for strontium modified Al–7%Si (LM25) cast alloy treated with bismuth. The results show that addition of bismuth in strontium modified alloys may have a poisoning effect resulting in lost modification of the silicon phase. With increasing Bi/Sr ratio, thermal analysis measurements showed that the eutectic growth temperature increased remarkably to 573°C and recalescence decreased to 0·2°C and the morphology of silicon displayed the same flake-like structure as in the unmodified alloys. Microstructural observation showed that a minimum Bi/Sr ratio of 1·2 which is equivalent to a Sr/Bi ratio of 0·43 is required for effective strontium modification and neutralization of the poisoning effect of bismuth.

Keywords

Thermal analysis bismuth modification aluminium alloy 

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Copyright information

© Indian Academy of Sciences 2011

Authors and Affiliations

  1. 1.Materials Engineering DepartmentFaculty of Mechanical Engineering, UTM SkudaiJohorMalaysia

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