SUITABILITY OF MOULDING MATERIALS FOR Al-Li ALLOY CASTING

Bastri Zeka; Boštjan Markoli; Primož Mrvar; Jožef Medved; Mitja Petrič

doi:10.17222/mit.2020.208

Bastri Zeka Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
Boštjan Markoli Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
Primož Mrvar Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
Jožef Medved Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia
Mitja Petrič Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia

DOI: https://doi.org/10.17222/mit.2020.208

Keywords: aluminium lithium alloy, reaction products, moulding materials

Abstract

The paper describes the production of an AlSi7Mg cast alloy with Li additions and the reactions of the melt with different moulding materials. It is known that Li is very reactive and tends to form various reaction products such as oxides, gases, etc., which can influence the casting quality. The aim of the research was to find a suitable way to produce such an alloy and to describe the reaction products that are formed between the melt and the moulding material and thus to find a suitable moulding material for processing Al cast alloys with Li additions. The melt was produced in an induction furnace under an inert atmosphere. After melting, 1 w/% Li was added and the melt was cast into five different mould materials consisting of graphite, steel, a CO₂ sand mixture, Croning mixture and calcium silicate materials. In the last three cases, various alcohol-based coatings were also used, such as graphite, zirconium oxide-graphite coating and aluminate-graphite filler coating. The results showed that the reaction products in the form of powder on the casting surfaces and the gas porosity in the castings occurred in the cast of a calcium silicate mould and sand mould mixtures. In the case of graphite and steel moulds, the casting surfaces were not oxidised, with no reaction products, and no gas porosity.

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