A comparative study of carbon additives on grain refinement of magnesium alloys

Cao, P., Qian, Ma, Kondoh, K. and StJohn, D. H. (2006). A comparative study of carbon additives on grain refinement of magnesium alloys. In: K. U. Kainer, Magnesium: Proceedings of the 7th International Conference Magnesium Alloys and Their Applications. Magnesium 2006: 7th International Conference on Magnesium Alloys and Their Applications, Dresden, Germany, (8-13). 6-9 November 2006.


Author Cao, P.
Qian, Ma
Kondoh, K.
StJohn, D. H.
Title of paper A comparative study of carbon additives on grain refinement of magnesium alloys
Conference name Magnesium 2006: 7th International Conference on Magnesium Alloys and Their Applications
Conference location Dresden, Germany
Conference dates 6-9 November 2006
Proceedings title Magnesium: Proceedings of the 7th International Conference Magnesium Alloys and Their Applications
Place of Publication Weinheim, Germany
Publisher Karger
Publication Year 2006
Sub-type Fully published paper
ISBN 9783527317646
3527317643
Editor K. U. Kainer
Start page 8
End page 13
Total pages 6
Language eng
Formatted Abstract/Summary To overcome the shortcomings of the superheating process (e.g. the high operating temperature and the applicability to relatively small volumes of melt only), post-1940s research on the grain refinement of magnesium alloys foucsed on developing an alternative method applicable to large volumes of melt at low operating temperatures. These efforts led to the discovery of the carbon inoculation process. A number of carbon based additives were tested for their grain refining potential, for example carbonaceous gases, soluid carbon or carbon-bearing powders and silicon carbides.

Following the discovery of the grain-refining effect of carbon additions, considerable efforts were made to develop a commercially reliable grain refiner for Mg-Al alloys. From an operational aspect, the carbonaceous gases and organic chlorides can be more readily introduced to magnesium melts than the solid carbon additives. In addition, bubbling a melt also helps to degas the melt. The addition of carbon in the form of C2Cl6 or Cl2-CCl4 blend was widely used before the 1970s because of the combined action of grain refining and degassing. The major problem of using carbonaceous gases, particularly chlorine-based gases, is the emission of chlorinated hydrocarbons (CHC). Other developments avoided gaseous additions. For example, Renger and Simon reported an effective grain refiner named Nucleant 5000, which appeared to work satisfactorily on AZ91 alloys. Wax-fluorspar-carbon grain refiners were developed earlier in England and recently in Canada. Liu et al. reported an Al4C3-SiC-Al alloy suitable for grain refinement of Mg-Al alloys such as AZ31 and AZ63. Motegi et al. recently disclosed a carbon grain refiner that contains either pure carbon powder or a mixture of carbon and Nb2O5 or V2O5 powder. However, to date no carbon-based grain refiners have proved reliable in delivering consistent grain refinement of Mg-Al alloys. This study compares the grain-refining effect of five carbon-based refiners provided by different suppliers (part of the experimental results were reported previously). The mechanism of grain refinement by carbon addition is discussed.
Subjects 09 Engineering
Q-Index Code EX
Additional Notes Presented during the session "Alloy Development I". K. Kondoh is not credited on this paper in the published programme.

 
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Created: Fri, 27 Nov 2009, 14:49:19 EST by Ms Lynette Adams on behalf of School of Engineering