Reverted austenite in PH 13-8 Mo maraging steels

Predicting microstructure and strength of maraging steels: Elemental optimisation

“…For the case of Al, Cu and Ti additions, it has been reported that their content in the reverted austenite is significantly lower, as they mainly partition to intermetallics forming before (underaging) than γ (overaging). For instance, Schnitzer et al [11] have reported in PH13 8Mo that the chemical composition in austenite is mainly composed by Fe, Ni and Cr, whereas Al content in the γ is less than 1 at%. Similarly, in the Mar6-13 series (Fe Ni Mn Al Cu steels), Kapoor et al [7] reported that most of the Al and Cu atoms partition to the intermetallics, although no reverted austenite composition was reported for the conditions tested.…”

“…For instance, the volume fraction of NiAl in Fe 8Ni 2Al (at%) is limited by Al (although Ni is controlling elemental interdiffusion), as there are less Al atoms available to form the intermetallic phase [11]; this implies that , with x 0 = 2 at% being the initial value for . For Ni 3 Ti, x 0 can be obtained using the CALPHAD software Thermocalc, by estimating the effective concentration of Ti diffusing to the particle: x 0 = x Ti,p f p,eq = 0.25f p,eq , where f p,eq is the predicted equilibrium volume fraction of Ni 3 Ti at a given composition and ageing temperature.…”

“…Galindo-Nava) its their application to other compositional scenarios. Additionally, thermokinetics methods have been applied to understand how the chemical composition affects intermetallic [11] and reverted austenite [12,13] evolution; however, these approaches have not provided a direct link with mechanical properties, including strength and elongation.…”

Simulation of Precipitation Kinetics and Precipitation Strengthening of B2-precipitates in Martensitic PH 13–8 Mo Steel

“…Schnitzer et al 2) have shown by 3D-atom probe tomography that the composition of the B2 precipitates evolves during the precipitation reaction. The initial nuclei showed remarkably higher Fe-and lower Al-and Ni-contents compared to the equilibrium composition, which is reached after more than 15 hours of ageing at 575°C.…”

“…In order to understand the relation between microstructure and mechanical properties, the evolution of ordered bcc-B2 precipitates (also denoted as β) and reverted austenite has been well characterized by 3D-atom probe, transmission electron microscopy (TEM) and tensile testing. [1][2][3][4] These experimental data form a suitable input for benchmarking the predictions of a physically-based thermokinetic model for precipitation kinetics simulations, which are performed in the present study. In addition to the evolution of phase fractions, radii and number densities of particles, we also obtain the evolution of the nucleus chemical composition, which, only after sufficiently long annealing time, approaches the equilibrium values.…”