Obtention rheocast structure for Al-4.5wt%Cu alloy: comparison ultra- refining and electromagnetic stirring

Purpose: the present work analyses the mechanisms involved in the formation of the rheocast (globular) structure for the Al-4.5wt%Cu alloy, produced by electro-magnetic stirring (EMS) of the liquid during solidification, under the following basic conditions: pouring temperatures of 750 and 800˚C with and without addition of a grain refiner. The objective is to directly compare between the electro - magnetic stirring and ultra - refining as methods of obtaining rheocast materials, as well as to verify the possibility of using these methods together. The general purpose is to develop a new Aluminum-Copper based alloy for thixoforming. Design/methodology/approach: the experimental apparatus was made of a wrapped metallic ingot mould surrounded by a sequence of induction coils and a power source that generated an estimated power of electromagnetic field with 1200Watts, which was enough for a fixed amount of 1kg of moulting metal). The macro and microstructures ingots obtained had the characterized by optical microscopy to measure the grain size, globular size and the roundness of the globular structures (to verify the efficiency of the globularization). Findings: In the present paper the combination of electromagnetic stirring, lower pouring temperature and grain refiner addition proved to be the best way to produce Al-5.5wt%Cu rheocast alloy. Research limitations/implications: the principal objective is to compare electro-magnetic stirring and ultrarefining to determine the better structure (level of globularization), determining the factor of larger influence: the grain refiner or the electro-magnetic induced field. Originality/value: Aluminum-Copper alloys specially designed for semi-solid applications are a new area in the semi-solid field, and this paper presents in primary hand the results for the AA 2xxx series.