Abstract
This research aimed to study an effect of cooling rates on T6 treatment process of B390 aluminium hypereutectic alloy. B390 casting samples were casted with pouring temperature of 710°C and solidified in three different cooling rates of 33.33, 28.60 and 22.22°C/s, respectively using three metal moulds. After that samples were subjected to T6 treatment: solution treated at 510°C for 30 min and aged at 200°C at various times. However, after ageing, hardness values of as-casted samples reduced with increasing cooling rate. It was found that the specimen cooled with the highest cooling rate exhibited the highest hardness. Peak hardness values of samples cooled with cooling rate of 33.33, 28.60 and 22.22°C/s after ageing obtained from ageing time of 3, 6 and 8 hour, respectively. Furthermore, the result showed that morphology of primary silicon, eutectic silicon and Ali5(Mn, Fe)3Si2 phase presented in the aged specimen cooled with the highest cooling rate exhibited more globular, finer and distributed more evenly compared with the slower cooled samples. It can be concluded that rapid cooling rate increases concentration of a-solid solution resulted in shorter aging time.
Highlights
Al-Si hypereutectic alloys are widely used for various applications due to its excellent properties
Al-Si alloys are normally casted by permanent mold casting, injection die casting and high pressure die casting (HPDC)
B390 is one of the Al-Si hypereutectic alloy which is widely used in automotive applications
Summary
Al-Si hypereutectic alloys are widely used for various applications due to its excellent properties. B390 is one of the Al-Si hypereutectic alloy which is widely used in automotive applications. B390 has high strength and good wear resistance due to the present of primary Si phase. Homogenously distribution of fine primary Si phase in the α phase of Al-Si Hypereutectic alloys are required. The major factor affecting size and morphology of the primary Si phase is cooling rate [1]. Because, casting cooling rate determines grain size, secondary dendrite arm spacing (SDAS), vacancies and the distribution of intermetallic compounds [2,3]. The solidification rate determines the cooling rate which has an effect on microstructure and mechanical properties of castings [6, 7, 8]
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