Microstructure vs. Near-threshold Fatigue Crack Growth Behavior of an Heat-treated Ductile Iron

Abstract

<p>Perferritic isothermal ductile iron (IDI®) is an intermediate grade between the low-strength grades of austempered ductile iron (ADI) and pearlitic ductile iron (DI) recently developed by Zanardi Fonderie Italy. IDI is produced by heat-treating an unalloyed nodular cast iron. The specific matrix microstructure is called “Perferritic” and consists predominantly of ferrite and pearlite. Compared to the pearlitic grades of nodular ductile iron, IDI combines similar strength with higher toughness as a result of the isothermal heat treatment.</p> In this contribution the fatigue crack growth resistance and <em>K_ath</em> of IDI are investigated and correlated to mechanical properties and microstructural features. The threshold <em>K_a</em> was determined using the load shedding technique as per ASTM Standard E-647 using CT specimens extracted from a cast block. Tensile specimens were extracted from the broken CT halves and used to determine the static mechanical properties. A metallographic investigation was carried out to correlate structural features and mechanical properties.<p>DOI: <a href="http://dx.doi.org/10.5755/j01.ms.18.1.1336">http://dx.doi.org/10.5755/j01.ms.18.1.1336</a></p

Statistical Data-Driven Model for Hardness Prediction in Austempered Ductile Irons

“…In Figure 4b it can be noted how in the sample treated at 290 °C for 90 min, αac needles converge at the same nucleation site, giving the appearance of αac needle bundles. Another type of αac needle arrangement consists of clusters, as observed in the sample treated at 320 °C for 90 min in Figure 4c, which is composed of parallel αac needles separated by γhC, similar to results of other researchers [40][41][42][43]. Meanwhile, Figure 4d,e illustrate the two types of αac needles, fine (lower ausferrite) and feathery (upper ausferrite), respectively, within the samples treated at 290 and 380 °C for 60 min, as reported by Putantunda and Olawale [19,44].…”

Marine Shaft Steels (AISI 4140 and AISI 5120) Predicted Fracture Toughness by FE Simulation

“…Characterization of materials is usually done using experimental routines [6] which can be complemented and, in some cases, even substituted with numerical prediction of material properties [7 -11] with the use of powerful computers and numerical analysis routines.…”