The constant need for the development of new alloys with an improved ratio between weight and strength is the driving force for the progress of the present work, which deals with the production of a ...new Al-cast alloy with the addition of lithium (Li). 0.8 wt% Li was added to the AlSi7Mg alloy. The solidification behaviour of such a new alloy was the focus of the work. The melt was produced in an inert gas atmosphere in an induction furnace. The solidification behaviour was described by CALPHAD simulations, optical microscopy, scanning electron microscopy (SEM) and simple thermal analysis. In addition, the Vickers hardness (HV) was measured 29 days after casting and compared with the results of the AlSi7Mg base alloy. Solidification proceeds somewhat differently from the base alloy, where the liquidus temperature is raised to 637 °C, where the primary AlLiSi phase forms, followed by αAl dendrites, eutectic βSi and other phases in the form of eutectics, which are known to occur during solidification of the AlSi7Mg alloy. The hardness of the new alloy is increased compared to the base alloy, especially at higher cooling rates, where the hardness gain is up to 36%.
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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