Investigating On The Performance Characteristics And Reuse Of Lost-form Casting Magnesium Alloy Scrap

In recent years, magnesium alloy has been widely used for automobiles, electronics and other industries, for its light density and excellent performance. At the same time, the lost foam casting (LFC) process is a precision forming technology capable of casting complicated parts with low manufacturing costs, and researches have showed that this process is also very suitable for magnesium alloy shape characteristics. LFC Magnesium alloy scraps are accreted serious oxide slag, paint and sticky sand on the surface, how to reuse the scraps effectively may be one of the keys that LFC process is used in the magnesium alloy casting. In this paper, it has been investgated that the performance characteristics of the AZ91 magnesium alloy scrap by the LFC, and then it have been get that the methods and procedures to reuse the scrap.Firstly, the LFC magnesium alloy scrap surface features are analyzed in this paper. Compared with die-casting Mg alloy scrap, the surface quality and internal quality of LFC Mg alloy scrap is poorer, and the surface of LFC Mg alloy scrap is easy to be affixed on the surface with quartz sand, spcial paint, and the gaseous and foggy pyrolysis products of EPS foam, also the internal quality of the LFC parts is not as good as the Die-casting parts.Secondly, it has been tested that performances and characteristics of the LFC Mg alloy scrap by remelting and casting. The LFC Mg alloy scrap belongs to belonging to scrap with the surface oxidation, and its microstructure consist of dominantα-Mg andβ-Mg17Al12 as well as a new phase Al7Mn6 and dregs. The higher remelt temperature, the higher mechanical property and corrosion resisting property; but it is not enough to reuse commendably the Mg alloy scrap only depending on remelting.Thirdly, it has been carried out that investigations of the LFC Mg alloy scrap reuse, and concrete works include: (1) By adding new Mg alloy in different proportions to test the mechanical performance and corrosion-resisting properties of the remelt scrap, and find that the quantity of inclusion has increased and the mechanical performance and corrosion-resisting properties reduced as the proportion of new Mg alloy reduced. (2) Once more refining after mischmetal (MM) added into the remelt scraps, the harm mixed can be effectively alleviated. (3) Mechanical vibration can significantly thin the microstructure of AZ91 alloy, and also make dregs become smaller and distribute evenly in crystal grain.Finally, the better process of reuse the LFC Mg alloy scraps was summarized as blow: LFC Mg alloy scraps - surface treatment - melt at lower temperature-refined at higher temperature - added other elements (for exmple MM) - refined again - standing and adjusting temperature - pouring (vibration) - performance tests.