Effect of Processing Parameters on the Mechanical Properties of Alloyed/Unalloyed ADI

Abstract

Two types of Spheroidal Graphite (SG) cast iron samples with different weight percentage of copper were austempered at four different temperatures. The austempering temperatures were 200°C, 300°C, 350°C, 400°C. The effect of austempering parameters (i.e. time and temperature) on the mechanical properties of spheroidal graphite iron was investigated as a function of austempering time and temperature. XRD analysis was also carried out to study the formation of different phases during isothermal transformation at different austempering conditions. Graphite morphology was studied by SEM. It was found that both the austenite (111) and ferrite (110) lines could be identified nearly in all cases. The maximum intensity of the austenite (111) line is increasing with increasing temperature but ferrite (110) line is increasing with increasing austempering time and decreasing with austempering temperature. Hence austempering calls for very precise control of process variables (austempering time and temperature). It has been found from the result that ADI having the alloying element copper (grade N2) achieved significant mechanical properties as compared to other grade (Nl) throughout the different austempering process adopted in this study.