Phase-Field Modeling of Precipitation Growth and Ripening During Industrial Heat Treatments in Ni-Base Superalloys
- PDF / 1,084,471 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 58 Downloads / 206 Views
Phase-Field Modeling of Precipitation Growth and Ripening During Industrial Heat Treatments in Ni-Base Superalloys MICHAEL FLECK, FELIX SCHLEIFER, MARKUS HOLZINGER, and UWE GLATZEL We develop a phase-field model for the simulation of chemical diffusion limited microstructure evolution, with a special focus on precipitation growth and ripening in multicomponent alloys. Further, the model accounts for elastic effects, which result from the lattice-misfit between the precipitate particles and the parent matrix phase. To be able to simulate particle growth and ripening in one dimension, we introduce an extra optional driving-force term, which mimics the effect of curved interfaces in one dimension. As a case study, we consider the one-dimensional (1D) c¢-precipitation growth and ripening under the influence of a realistic multistep heat treatment in the multicomponent Ni-based superalloy CMSX-4. The required temperature-dependent thermodynamic and kinetic input parameters are obtained from CALPHAD calculations using the commercial software-package ThermoCalc. The required temperature-dependent elastic parameters are measured in-house at the chair of Metals and Alloys, using resonance ultrasound spectroscopy and high-temperature X-ray defraction. Finally, the model is applied to calculate the equilibrium shape of a single c¢-particle with periodic boundary conditions. Relations to the shapes of c¢-particles in respect of heat-treated experimental microstructures are discussed. https://doi.org/10.1007/s11661-018-4746-5 The Minerals, Metals & Materials Society and ASM International 2018
I.
INTRODUCTION
NICKEL-BASED superalloys have various applications at elevated temperatures, especially in stationary gas turbines and aero-plane engines. The main strengthening mechanism, which makes these alloys applicable for high temperatures is particle strengthening by coherent precipitations. The most prominent case is the c¢ strengthening of Ni-based superalloys for turbine blades. Typically, these blades are casted as single crystals. Subsequently, heat treatments are employed to establish the characteristic two-phase precipitation microstructure, which consists of coherent, cuboidal c¢-precipitate particles embedded in the fcc matrix solution-phase.[1] The phase-field method is widely considered to be a very powerful tool for modeling microstructure-evolution, such as solidification[2,3] as well as solid-state transformations.[4–7] In thermodynamic-consistent phase-field
MICHAEL FLECK, FELIX SCHLEIFER, MARKUS HOLZINGER, and UWE GLATZEL are with Metals and Alloys, University Bayreuth, Ludwig-Thoma-Straße 36b, 95447 Bayreuth, Bavaria, Germany. Contact e-mail: michael.fl[email protected] Manuscript submitted March 22, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
modeling of precipitation growth, we start from a thermodynamic functional, which is an integral over a local phenomenological potential energy density. This phenomenological energy density can include many different energetic effects such as an interfacial part, which acc
Data Loading...
