The influence of remelting parameters on Mg alloy/glassy carbon suspension stability
Anita Olszówka-Myalska
Quarterly No. 2, 2014 pages 96-100
DOI:
keywords: magnesium matrix composite, glassy carbon, stir casting, die casting
abstract The homogenous distribution of reinforcing phases in a liquid metal matrix determines the final properties of composite elements fabricated by the casting of a suspension. Ensuring not only a proper temperature and stirring conditions during suspension preparation, but also a relatively short time between the end of mixing and the start of suspension pouring into moulds is critical. In the article, investigations focused on the migration of glassy carbon particles (GCp) in two melted magnesium alloys, Mg3Al and Mg2ZnZrRE, were presented. The composites previously obtained by the stir casting method were remelted at the temperatures of 610, 640, 690 and 730°C (time 30, 60 and 90 min) and finally cooled at a temperature of 20°C. The particles segregation on the macro scale was analyzed on a longitudinal section of the obtained samples. It was revealed that both types of suspensions were stable at 610 and 640°C but at 690 and 730°C, a loss of stability was observed. In spite of the slightly less density of the glassy carbon than the applied magnesium alloys, the type of segregation was different and depended on the alloy chemical composition. In the suspension of Mg3Al-GCp, particle migration to the crucible top was observed only, while in the Mg2ZnZrRE-GCp suspension, two zones with a high particle concentration were formed, separated by a zone of pure metal.