Fabrication of Aluminium Composite...

FABRICATION OF ALUMINIUM COMPOSITE FROM
RECYCLED AUTOMOTIVE COMPONENT

M.N Mazlee
mazlee@unimap.edu.my


ABSTRACT

The fabrication of aluminium composite has been carried out by using a recycled aluminium automotive component. The recycled aluminium engine blocks (Al-Si alloy) have been chosen as a matrix for the composite. The commercial silicon carbide (SiC) particles have been used as the reinforcement. The composition of recycled aluminium alloy and SiC particles were melted via turbulence casting technique using oil-fired non-ferrous melting furnace. The molten aluminium composite was cast into the shape of brake disc via sand casting process. The recycled aluminium composite brake disc has been found to have a significant weight reduction which is about only one-third of the conventional cast iron brake disc comparatively.
Keywords : recycled aluminium engine block, SiC particles, turbulence casting, sand casting, brake disc.


INTRODUCTION

Aluminium has been recycled since the days it was first commercially produced and today recycled aluminium accounts for one-third of global aluminium consumption worldwide. Recycling is an essential part of the aluminium industry and makes sense economically, technically and ecologically [1]. Currently, aluminium is used for structural, automotive components and aerospace fuselage. The others main markets are engineering, packaging and building. The use of aluminium in transportation sector especially for automotive applications is expected to grow in Malaysia for the future years. There is a possibility remelting recycled aluminium from automotive component and combined with reinforcement to produce aluminium matrix composite with better desired mechanical properties.

Aluminium matrix composites reinforced with ceramic particulate are well known for their higher specific modulus, strength and wear resistance as compared with conventional alloys [2,3]. One of the major driving forces for the technological development of aluminium matrix composites reinforced with ceramic particles is a result of these composites posses superior wear resistance and is hence potential candidate materials for a number of tribological applications. Applications in which materials are subjected to mechanical wear include pistons and cylinder liners in car engines and automotive disk brakes in vehicles [2,4]. Aluminium based metal composites offer a very useful combination of properties for brake system applications in replacement of cast iron. Specifically, the wear resistance and high thermal conductivity of aluminum metal composites enable substitution in disk brake discs and brake drums, with a significant weight savings on the order of 50 to 60%. The weight reduction will reduce the inertial forces thus providing an additional benefit in fuel economy. In addition, lightweight metal composite brake discs provide increased acceleration and reduced braking distance. It is reported that, based on brake dynamometer testing, metal composite reduce brake noise and wear, and have more uniform friction over the entire testing sequence compared to conventional commercial cast iron brake disc.

A number of automobiles now use MMC brake components. The Lotus Elise used four discontinuously reinforced aluminium brake discs per vehicle from 1996 to 1998, and the specialty Plymouth Prowler has used DRA in the rear wheels since production started in 1997. Discontinuously reinforced aluminum brake discs are particularly attractive in lightweight automobiles and are featured in the Volkswagen Lupo 3L and the Audi A2. In addition, a number of electric and hybrid vehicles, such as the Toyota RAV4, Ford Prodigy, and the General Motors Precept, are reported to use MMC brake components [5].

Previous researches related to the recycled aluminium composites were such as recycled aluminium matrix composites reinforced with Inconel 601 fibres [6], recycled of AlSiMg–SiCp composite [7], recycling of aluminium alloy and aluminium composite chips AA6061/Al2O3 [8] and recycled aluminum-alloy scrap with Saffil ceramic fibers [9]. There is no research concerning aluminium composite from the combination of recycled engine block and SiC particle. The objective of this research is to fabricate the aluminium composite brake disc by using the recycled aluminium engine blocks with the addition of commercial SiC particles.


MATERIALS AND EXPERIMENTAL PROCEDURE

The recycled aluminium engine blocks (Al-Si alloy) have been used as a matrix material. The commercial SiC particles size ranging from 10 to 20 mm have been used as the discontinuous reinforcement.

The recycled aluminium engine blocks were cut into pieces to facilitate the placing in the graphite crucible. Then, SiC particles were preheated at 500 ± 5°C before put together with the recycled aluminium engine blocks before casting process can be carried out. Magnesium has been added to the composition to increase the wettability of the SiC particles and aluminium matrix. Prior to casting process, sand casting mould was prepared by using silica casting sand and sodium silicate which acts as a binder. Both materials were mixed by using the electric mixer. Then, the sand mould was compacted manually and hardened by using a carbon dioxide (CO2) gas as shown in Figure 1. Polystyrene foam has been used as the pattern materials and cut into the shape of brake disc together with the design of sprue, riser and runner.



Melting process was carried out in the self-design and self-made oil-fired non-ferrous melting furnace. Turbulence casting technique was used to ensure the homogeneity of the SiC particles in the aluminium composite. The molten composite was heated until the melting process has reached the superheating condition. After that, the molten recycled aluminium composite was poured into the sand mould as shown in Figure 2. Finally, the cast aluminium composite product was machined by lathe machining to produce the recycled aluminium composite brake disc to the same size of commercial conventional cast iron brake disc as shown in

Figures 3 and 4.

RESULTS AND DISCUSSION

Figures 3 and 4 show top and bottom view of the recycled aluminium composite brake disc and commercial cast iron brake disc respectively. From the observation, the surface of aluminium composite brake disc has a bright and shiny appearance compared to commercial cast iron brake disc. In general, sound casting has been produced throughout the aluminium composite brake disc due to the effective turbulence casting technique that been applied during the melting process. Less porosity also has been observed when the cross section of the produced composite was analysed. Uniformly distributed porosity at the bottom surface (Figure 4) of the recycled aluminium composite brake disc was a unique feature that was attributed by the entrapped air in the polystyrene foam which has been released during the casting process. The aluminium composite brake disc that has been produced has a significant weight reduction which is about only one-third of the conventional cast iron brake disc comparatively. Quantitavely, the weight of recycled aluminium composite brake disc and conventional cast iron brake disc were 0.85 kg and 2.5 kg respectively.

CONCLUSION

In our present fabrication, we can conclude that the aluminium composite brake disc derived from recycled aluminium engine blocks has been found to have a significant weight reduction which is about only one-third of the conventional cast iron brake disc comparatively.


REFERENCES

[1] Aluminium the Material. Retrieved on 23th February 2003 from http://www.world-aluminium.org/production/recycling/index.html.
[2] Garcia-Cordovilla C., Narciso J. & Louis E., Abrasive wear resistance of aluminium alloy/ceramic particulate composites, Wear, 1996; 192: 170-177.
[3] Peng Yu, Cheng-Ji Deng, Nang-Gang Ma & Dickon H.L. Ng, A new method of producing uniformly distributed alumina particles in Al-based metal matrix composite, Materials Letters, 2003.
[4] Iwai Y., Honda T., Miyajima T., Surappa M.K. & Xu J.F., Dry sliding wear behaviour of Al2O3 fiber reinforced aluminium composites, Composite Science and Technology, 2000; 60: 1781-1789.
[5] Automotive Applications of Metal-Matrix Composites. Retrieved on 24th September 2003 from http://www.asm-intl.org/pdf/spotlights/AutoApp.pdf
[6] J. Lapin & T. Pelachova´, Microstructure and mechanical properties of wrought aluminium alloy prepared by recycling of aluminium matrix composites reinforced with Inconel 601 fibres, Materials Science and Engineering, 1999; A271: 266–274.
[7] L. Ceschini, C. Bosi, A. Casagrande & G.L. Garagnani, Effect of thermal treatment and recycling on the tribological behaviour of an AlSiMg–SiCp composite, Wear, 2001; 251: 1377-1385.
[8] J.B. Fogagnolo, E.M. Ruiz-Navas, M.A. Simón & M.A. Martinez, Recycling of aluminium alloy and aluminium matrix composite chips by pressing and hot extrusion, Journal of Materials Processing Technology, 2003.
[9] M. Samuel, Reinforcement of recycled aluminum-alloy scrap with Saffil ceramic fibers, Journal of Materials Processing Technology, 2003.