Cold compression in direct recycling of aluminium 6061
In conventional recycling method, the aluminium scrap undergoes melting process whereby only 52% of the aluminium are recycled and the others are wasted in terms of melting loss, dross, extrusion scraps and etc. Other than material loss, the energy usage needed for conventional process are very high...
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| Format: | Thesis |
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2016
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| Online Access: | http://eprints.uthm.edu.my/9051/ http://eprints.uthm.edu.my/9051/1/Chan_Boon_Loong.pdf |
| Summary: | In conventional recycling method, the aluminium scrap undergoes melting process
whereby only 52% of the aluminium are recycled and the others are wasted in terms
of melting loss, dross, extrusion scraps and etc. Other than material loss, the energy
usage needed for conventional process are very high with energy consumption of
6000 kcal/kg and high operation costs due to the large number of operation. This
research focus on one of the least researched direct recycling method that is by cold
compression. Only one optimum chip size was used, that is (4-6) mm x (3.5-4.5) mm
x (1.45-1.55) mm. The chips were cold compressed with a Force (F) of 35, 40 and 45
tons with variable in Holding Time (t = 1, 5 and 10 minutes). The compressed
samples were then placed into the furnace to be sintered at different Temperature (T)
namely, 0°C (no sintering), 500°C and 600°C. Both the mechanical properties
(Ultimate Tensile Strength, UTS and Elongation to Failure, ETF) and the physical
properties (Density, D and Micro-hardness, MH) were then tested. Response surface
methodology (RSM) was then applied to identify the optimal variable parameters for
specific goals. It was found that an increased in the compression force above the
optimum condition will not bring any significant outcome on the compressed
specimen. Whereas, sintering process increases the UTS to maximum of 14.67 MPa
at sintering temperature of 600°C. But at the same time, the specimen that was
sintered at 600°C show low ETF of only 1.23%. As for specimen that were not
sintered (0°C), the lowest recorded UTS is 2.77 MPa but having better microhardness
that was even higher if compared to the reference specimen with microhardness
of 117.10 HV. Even though there is an improvement in mechanical and
physical properties but the microstructure of the sample reveal that there is lack of
bonding in the structure as the chips were more to overlapping each other rather than
inter-locking one another. Further improvement in terms of shear deformation like
hot extrusion is highly recommended to ensure better material bonding and powder
metallurgy may be one of the other ways to strength the recycled chips as powdered
aluminium sintered better than aluminium chips. |
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