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LIGHTWEIGHT ULTRA-STRENGTH ALUMINIUM FLAT PRODUCTS FOR LOW ENVIRONMENTAL IMPACT APPLICATIONS FABRICATED BY SEVERE PLASTIC DEFORMATION AND COLD ROLLING

Nicolae Serban

Abstract

It is well known that the use of aluminium and its alloys in transports, aeronautics or in the car industry as a vehicle downweighting material, also decreases fuel and energy consumption and lowers greenhouse gas emissions. In our study, an innovative thermomechanical processing technology for obtaining flat ultra-strength aluminium products by subsequent cold rolling after equal channel angular pressing (ECAP) was proposed and experimented. ECAP is an advanced severe plastic deformation (SPD) method for controlling the microstructure when manufacturing bulk ultrafine grained (UFG) materials and nanomaterials (NM) in which a billet is pressed through a die containing two channels of equal cross-section intersecting at a certain angle. The sample experiences simple shear deformation at the intersection, without any precipitous change in the cross-sectional area (the die preventing lateral expansion), allowing repeated pressings for several cycles and the possibility to impart extremely large strains. In this study, a commercial 6063 aluminium alloy (initially softened back to temper O) was subjected to SPD processing using a 100пїЅ ECAP die. The specimens were processed at room temperature for one, two, three and respectively four passes, using the BC processing route (rotated counter clockwise 90пїЅ after every pass). All ECAP treated samples and one unprocessed sample (in the initial O temper) were further cold rolled up to an 80% thickness reduction. All samples were microstructural investigated (scanning electron microscopy пїЅ SEM) and mechanically tested in tensile tests, the ultimate tensile strength, yield strength and maximum elongation to fracture being determined. It was shown that grain refining by means of ECAP processing, as an initial treatment prior to cold rolling, results in a significant improvement of mechanical characteristics for the final flat products, therefore arising the possibility to reduce the dimensions of the products, which leads to a decrease in the weight of the vehicles and consequently to fuel savings and higher payloads, the obtained ultra-strength characteristics being highly desirable when manufacturing sustainable lightweight aluminium flat products for low environmental impact applications.

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DOI resolver: doi.org/10.5593/sgem2017h/63/s24.003

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