Improved grain size prediction in aluminium-silicon alloys by thermal analysis

J. Lacaze, Deni Ferdian, I. Lizarralde, A. Niklas, S. Eguskiza, A. I. Fernández-Calvo

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Grain refinement is a common practice in aluminium casting alloys, being Ti and/or B the most popular refining additions. The effectiveness of these additions may be controlled by thermal analysis consisting in analysing the cooling curve during solidification of a sample cast in an instrumented standard cup. This assessment is based on the use of a pre-established relationship between some characteristic parameters of the cooling curve and the microstructure features measured either on the cup or on a standard sample cast at the same time. Previous works showed there is still a need for improving the prediction in the range of small grain sizes in case little or no recalescence is observed. tf, Th-Al, the recalescence time or the time during which temperature remains constant, has been established as an appropriate parameter to take into account high nucleation potential of the melts. This work reports a statistical analysis performed on the characteristic features of the cooling curves of 110 melts of AlSi7Mg alloy. A first analysis gave a simple linear relation between grain size and tf, Th-Al with a correlation coefficient R2 of 0.91, that shows a satisfactory agreement for the fine and medium grains (up to 1 mm) while being less good for very coarse grains. However, coarse grains are easily detected; thus, corrective actions can then be taken in order to improve the metallurgical quality in terms of grain size refinement before casting. Further analysis led to express tf, Th-Al as a function of recalescence and of the grain size, its square and cube. The correlation coefficient is much better at 0.96 with an improved description in both small and large grain domains.

Original languageEnglish
Title of host publication71st World Foundry Congress
Subtitle of host publicationAdvanced Sustainable Foundry, WFC 2014
PublisherWorld Foundry Organization
ISBN (Electronic)9788461700875
Publication statusPublished - 1 Jan 2014
Event71st World Foundry Congress: Advanced Sustainable Foundry, WFC 2014 - Bilbao, Spain
Duration: 19 May 201421 May 2014

Publication series

Name71st World Foundry Congress: Advanced Sustainable Foundry, WFC 2014

Conference

Conference71st World Foundry Congress: Advanced Sustainable Foundry, WFC 2014
CountrySpain
CityBilbao
Period19/05/1421/05/14

Keywords

  • AlSi7Mg alloys
  • Grain refinement
  • Multivariate analysis
  • Nucleation potential
  • Thermal analysis

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