Effects of Carbides on Fatigue Characteristics of Austempered Ductile Iron
نویسندگان
چکیده
Crack initiation and growth behaviour of an austempered ductile iron (ADI) austenitised at 800C and austempered at 260C has been assessed under three point bend fatigue conditions. Initiation sites have been identified as carbides remaining from the as cast ductile iron due to insufficient austenisation. The number of carbides cracking on loading to stresses greater than 275 MPa is critical in determining the failure mechanism. In general, high carbide area fractions promote coalescence dominated fatigue crack failure whilst low area fractions promote propagation dominated fatigue crack failure. Individual carbides have been characterised using finite body tessellation (FBT) and adaptive numerical modelling (SUpport vector Parsimonious ANalysis Of VAriance (SUPANOVA)) techniques in an attempt to quantify the factors promoting carbide fracture. This indicated that large or long and thin carbides on the whole appear to be susceptible to fracture, and carbides that are locally clustered and aligned perpendicular to the tensile axis are particularly susceptible to fracture.
منابع مشابه
Carbide Precipitation in the Microstructures of Austempered Ductile Irons Containing 0.48% and 4.88% Al
The influence of aluminium on the microstructure of austempered ductile cast iron (ADI) has been studied. The presence of well distributed graphite in the matrix, and a relatively high volume fraction of retained austenite are responsible for the good mechanical properties of the Aluminium alloyed austempered ductile irons including excellent wear resistance, higher resistance to thermal shock,...
متن کاملStructural and Mechanical Characterization of Austempered Cu - Sn Ductile Iron Alloys
The effect of heat treatment and alloying elements of copper and tin on the microstructure and mechanical properties of austempered ductile cast iron alloys is investigated. The austenitizing temperature of 890°C, the isothermal transformation (austempering) temperatures of 285, 335 and 375°C, and austempering times of 15, 30, 75 and 150 minutes are studied. The alloying elements of copper and ...
متن کاملOptimizing the Microstructure and Mechanical Properties of Austempered Ductile Iron for Automobile Differential Gear
Austempered ductile iron (ADI) has been proved to be an excellent material as it possesses attractive properties: high strength, ductility and toughness combined with good wear resistance and machinability. These properties can be achieved upon adequate heat treatment which yields the optimum microstructure for a given chemical composition. The heat treating of the ductile cast iron produces th...
متن کامل