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Samples of ductile iron alloyed with 0.88 % Ni with a nodule count of 606, 523, and 290 nod/mm2 were obtained from sand cast plates of different thickness in the range from 8.46 to 25.4 mm. The effect of the nodule count was evaluated during the austempering process held at 285?C and austempering times of 15, 30, 45, 60, 70, and 90 min. The volume fraction of high carbon austenite was increased when the nodule count was increased, however, the carbon content of the high carbon austenite kept almost constant. The process window was narrow, requiring a lower austempering time when the nodule count was increased. The combination of a higher nodule count and low austempering temperature allows obtaining a fine ausferritic microstructure which leads higher Brinell hardness and tensile strength. The process window was determined by XRD measurements and it is in good agreement with the microstructural and hardness evolution as the austempering time was increased.

Influence of nIckel addItIon and caStIng ModuluS on the propertIeS of hypo-eutectIc ductIle caSt Iron e. colin-garcía a , a. cruz-ramírez a* , g. reyes-castellanos a , J.a. romero-Serrano a , r.g. Sánchez-alvarado a , M. hernández-chávez b a

The present study focuses on the effect of various degrees of plastic deformation generated by cold radial forging on the mechanical properties and the fracture morphology of 32 CDV 13 steel. The cold forging percentage was evaluated for 17.45, 33.30, 42.0 and 46.47 %. The microstructural analysis of the steel shows tempered martensite. The tensile strength, yield strength and hardness were found to increase with the increase of cold forging percentage due to the energy stored in the material during cold forging. For higher cold forging percentage, the toughness of the material was decreased according to the reduction of absorbed energy obtained during deformation. Fractography of the Charpy impact specimens shows a surface roughness and dimple pattern for the steel as was acquired and for 17.45 and 33.3 % of cold forging; while for 42 and 46.47 % of cold forging a cleavage fracture pattern was observed.