SELECTED PROBLEMS OF A TECHNOLOGY OF THE AZ91 MAGNESIUM ALLOY MELT TREATMENT

As expected, the increasing demand for magnesium alloy castings has already become a fact. Considering this situation, a rich program of the studies on this particular subject has been initiated and put into operation at the Foundry Research Institute. The studies mainly include the development of new alloys along with the technologies of their casting. A good example are here the ultralight alloys (e.g. magnesium-lithium alloys). The addition of special alloying elements requires the development of new and original melting and casting technologies. Various investigations are also carried out on the new melt protecting and refining techniques. The present article comprises the results of the studies carried out recently by the Department of Non-Ferrous Metals operating in the Foundry Research Institute in Cracow. The aim of the studies was to develop for magnesium alloys and respective composite materials a complex technology ofmolten metal treatment and casting into the sand and metal moulds, followed by heat treatment. The program of the studies has been divided into several stages; the first stage was related with the technology of molten magnesium alloys treatment and refining. Complex studies covered only one alloy, i.e. AZ91, since in the family of magnesium alloys this one is the most popular and most widely used; it can be cast equally well into sand moulds and metal moulds by both pressure and gravity process. At the first stage of the investigations, the technology of melting and melt protection from the selfignition was developed. The effect of the gas mixture of a new composition on the refining process during casting into sand and metal moulds was examined. The effectiveness was determined from the macro- and microstructure density.

Download 1.21 MB >>