Mechanical characterization and optimization of heat treatment parameters of manganese alloyed austempered ductile iron

Abstract

Austempered Ductile Iron (ADI) belongs to the family of cast irons whose mechanical properties are altered using austempering heat treatment process. The objective of this paper is to study the effects of heat treatment parameters on manganese alloyed ADI. Hence, austenitization temperature, austempering temperature and austempering time are taken as the control variables along with the manganese content in the material. The effects of heat treatment are studied by measuring the ultimate tensile strength and the hardness of the material.  The regression equations are developed to relate the various parameters under study. The microstructures of the specimen reveal that retained austenite content increases with increase in manganese and results in decrease in hardness of the material. The statistical analyses indicate that the austempering temperature is the major factor affecting the variation in hardness and tensile strength with 74.5 % of contribution within the range of values whereas,  variation in manganese content does not have significant effect on hardness within the investigated composition range in the material.