The Effects of Heat Treatment Parameters on the Microstructures of Aluminium Ductile Cast Iron

The effects of the heat treatment parameters on the microstructure of dual matrix structure (DMS) Aluminium Ductile Irons has been investigated in this research. The samples were cast and full annealing heat treatment was carried out in order to produce ferritic structure. The samples preheated at 600 °C for 10 minutes، followed by austenitising at 2 temperatures (920 °C، 950 °C) in motlen aluminium for various times (1 minutes to 15 minutes)، followed by oil-quenching. Scaning Electron Microscopy (SEM) and Optical Microscopy (OM) were used to evaluate the distribution of martensite in matrix. The results revealed that martensite is created in the intercellular regions at shorter partial austenitizing times، nevertheless، it is also formed around spherical graphites by increasing the partial austenitizing time. Moreover، it is seen that raising the temperature at a constant partial austenitizing time will increase the volume fraction of the martensite and totally، the rate of creating of the martensite in 950 °C is more than that in 920 °C. In addition، the volume fraction of the martensite at 950 °C and 4 minutes was obtained to maximum of 90. 7%.