The influences of Austempering Temperatures on Microstructures and Mechanical Properties of Austempered 1.5%Ni-0.3%Mo Ductile Iron

The objective of this research is to study the effects of process parameters on microstructures and mechanical properties of Austempered Ductile Iron (ADI) 1.5 %Ni- 0.3 %Mo. Processing parameters to be study were austenitizing and austempering temperatures and austempering time. It was found that increasing austenitizing temperature resulted in slow transformation rate and coarse structures. Increasing austempering temperature to above 350 “C gave the upper bainite structures and below this temperature, the lower bainite was obtained. The optimum mechanical properties of AD1 were found to be critically dependent on austempering time. For 2.5 mm specimen thickness,the highest tensile strength was obtained by austenitizing at 900 “C and austempering at 300 “C for 2 hours. Hardness and tensile strength of the ADI were found to be 3 13 - 4 2 6 HB and 7 1 O-1050 MPa respectively. The result showed that quality castings and proper heat treatment were required for optimum mechanical properties of the ADI.