Influence of cooling rate on the amount of graphite nodules and interlamelar space in perlite phase in a ductile iron

Abstract

The microstructures of a ductile iron solidified under six different cooling rates have been studied, using optical microscopy (OM), scanning electron microscopy (SEM) and tensile test. Results show that cooling rates increase from 0.58 to 0.95°C/s, so perlite growth temperature (<em>T</em>_PG) decreases, nodules size (<em>N</em>) decreases and nodules per volume (<em>N</em>_v) increases. Perlite interlamellar spacing (λ) between cementite and ferrite, shows no significant change. Finally, as cooling rate increases, yield and tensile strengths increase, but the hardness shows a minimum increase.