**5. References**


powder coating cycles on the microstructure and mechanical properties of the 18-inch

Based on the results obtained in the present study, it can be drawn that the different cooling rate of the wheels, ejected from the die at high temperature, produces different amount of distortions. By increasing the water temperature, the amount of distortions linearly decreases. Water cooling at a temperature higher than 70°C produces similar distortion as

Considering the T6 heat treatment applied to the wheel production, a solution heat treatment of 6 h at 540°C is sufficient to dissolve completely the Mg-rich phases and to achieve a homogeneous solid solution. This solution treatment causes spheroidization and coarsening of the eutectic Si particles, leading to substantial changes in the microstructure throughout the 18-inch wheel. Higher solution temperatures lead to incipient melting at grain boundary and in the interdendritic regions. On quenching this liquid, reprecipitation of silicon and other intermetallic particles occur, and the average size increases. Quenching also leads to a large amount of shrinkage porosity adjacent to melted regions, which can

Furthermore, quenching is usually carried out from solution temperature to room temperature to obtain a supersaturated solid solution of solute atoms and vacancies, in order to achieve an elevated strengthening subsequent ageing. Here, the wheel distortion progressively reduces by increasing the temperature of water quenching, and a temperature higher than 80°C is sufficient to avoid distortion, allowing to achieve at the same time the

Finally, the powder coating of the wheels influences the final mechanical properties by activating the diffusion mechanism of the solute atoms, such as Mg and Si. This leads to the precipitation of dissolved elements and the coarsening of existing precipitates. The result is an increase of the hardness of about 3% after each coating cycle. This means that the powder coating can be integrated into the whole T6 heat treatment cycle of wheels, with a great

Alexopoulos N.D. & Pantelakis S.G. (2004). Quality evaluation of A357 cast aluminium alloy

Apelian D., Shivkumar S. & Sigworth G. (1989). Fundamental aspects of heat treatment of

ASM Metals Handbook (1990). *Properties and Selection: Nonferrous Alloys and Special-Purpose* 

ASM Metals Handbook (1991). *Heat treating*, Vol.4, ASM International, ISBN 978-087-1703-

Auburtin P. & Morin N. (2003). Thermo-mechanical modeling of the heat treatment for

Bates C.E. (1987). Selecting quenchants to maximize tensile properties and minimize

cast Al-Si-Mg alloys. *AFS Transactions*, Vol.97, pp. 727-742

specimens subjected to different artificial aging treatment. *Materials and Design*,

*Materials*, Vol.2, ASM International, ISBN 978-087-1703-78-1, Materials Park, OH,

aluminium cylinder heads. *Mécanique & Industries*, Vol. 4, No.3, pp. 319-325, ISSN

distortion in aluminium parts. *Journal of Heat Treating*, Vol.5, No.1, pp. 27-40, ISSN

coalesce and lead to the complete fracture of the wheel.

impact on productivity and manufacturing cost of wheels.

Vol.25, No.5, pp. 419-430, ISSN 0261-3069

79-8, Materials Park, OH, USA

required mechanical properties.

**5. References** 

USA

1296-2139

0190-9177

wheels.

air cooling.


**Part 4** 

**Mechanical Behavior of** 

**Aluminium Alloys and Composites** 

