Abstract
This work concerns microstructural and mechanical properties of an austempered ductile cast iron (ADI). The ductile iron material was produced by the sand mould casting technique. Afterwards, austempering heat treatment was applied to the specimens at two different temperatures of 250°C and 350°C. Austempered Ductile Irons (ADIs) were produced successfully by different two-stage heat treatments, to obtain favorable microstructure and hardness. The microstructure and hardness obtained by such variable heat treatments were compared. The austempering temperature and time were found to be decisive parameters in obtaining a desired ADI microstructure.
Highlights
Austempered ductile iron (ADI) is considered as a new kind of engineering material and shows good combinations of high strength, ductility, toughness, fatigue strength and wear resistance
The attractive properties of ADI are due to its unique microstructure which consists of high carbon austenite and bainitic ferrite with graphite nodules dispersed in the matrix
Austenitization is followed by the second stage, (i.e) austempering, which consists of rapidly transferring the specimen from the furnace into a salt bath wherein isothermal transformation of austenite occurs over a period of time specified by the soaking time
Summary
Austempered ductile iron (ADI) is considered as a new kind of engineering material and shows good combinations of high strength, ductility, toughness, fatigue strength and wear resistance. Considerable research have been conducted on microstructure and mechanical performance of austempered ductile iron[1,2]. With the development of ADI, standards for ADI have been published. In ASTM standard 897 M-06, there are 6 grades of ADI according to the ultimate tensile strength [4, 12]. Researches on ADIs are related primarily to the austempering process parameters, viz., austempering time and temperature, rather than to the standard ADI strength grade, which can be confusing to the designer of ADI. Microstructure and properties of ADI with different strength grades should be studied in detail to supply useful information for the ADI makers and component designers. Four ADIs samples were prepared; the microstructure was analysed, and hardness tests were conducted and correlated with austempering parameters
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