Microstructural Characterization and Some Mechanical Behaviour of LowudManganese Austempered Ferritic Ductile Iron

摘要

This work studied the microstructural characterization andudmechanical behavior of low manganese Austempered DuctileudIron (ADI), with a view to improve the properties of iron andudto increase the areas of applications. Three sets of ductile ironudof specified composition were machined from Y-blocks toudtensile and hardness pieces. The samples were preheated atud350 0C for 1hr and austenitised at 900 0C for 1hr in salt bathudfurnace. The three sets of samples were immediatelyudaustempered in the austempering salt bath furnace at uniformudaustempering temperatures of 300 0C, 350 0C and 400 0C forud90, 120 and 150 minutes; each sample for each temperatureudwindow. All sets were prepared for metallographicudexamination; tensile and hardness tests were carried out. Theudresults showed that maximum hardness, tensile and yieldudstrength were obtained at austempering temperature of 350 0Cudand at 150 minutes. At 300 0C and 350 0C, it was noticed thatudthe hardness and strength increase with austempering time.udThe optimum tensile strength was 1300 MPa at 350 0C afterudaustempering for 150 minutes. In conclusion the austemperingudoperation has a significant effect on the mechanical andudmicrostructural properties of ADI.ud