Microscopic Analysis of the Aluminium Castings Produced with the use of Polymer Composite Patterns

Abstract

The paper presents a microscopic analysis of the surface and fracture of aluminium castings produced using the lost-wax method for patterns made of a composite material, i.e. polyethylene with the addition of bentonite. Castings are made of AlSi7 aluminium alloy (silumin) in a plaster mould. A new type of polymer waxes enriched with bentonite was used to obtain new composites, minimizing the defects caused by the casting production process. The castings were made in the centrifugal casting process. The prepared plaster moulds were removed from the furnace and poured with liquid aluminium alloy (AlSi7) at 750°C. The surface and fracture of the castings was analysed using an optical digital microscope type VHX-7000 manufactured by KEYENCE. It has been proven that the studied castings feature surface defects (raw surface defects) in the form of high roughness and the presence of bentonite inclusions classified as casting contamination. During the tests, shape defects related to mechanical damage were also detected.

Keywords

• casting
• aluminium alloys
• lost-wax method
• bentonite
• digital microscope