Application of Phase-Field Method to the Analysis of Phase Decomposition of Alloys

This chapter is focused on the application of the phase-field method to the analysis of phase decomposition during the isothermal aging of alloys. The phase-field method is based on a numerical solution of either the nonlinear Cahn-Hilliard equation or the Cahn-Allen equation. These partial differential equations can be solved using the finite difference method among other numerical methods. The phase-field method has been applied to analyze different types of phase transformations in alloys, such as phase decomposition, precipitation, recrystallization, grain growth, solidification of pure metals and alloys, martensitic transformation, ordering reactions, and so on. One of the main advantages of phase-field method is that this method permits to follow the microstructure evolution in two or three dimensions as the time of phase transformations progresses. Thus, the morphology, size, and size distribution could be determined to follow their corresponding growth kinetics. Additionally, the evolution of chemical composition can also be followed during the phase transformations. Furthermore, both Allen-Cahn and Cahn-Hilliard equations can be solved simultaneously to analyze the presence of ordered phases or magnetic domains in alloys

Simulación numérica de la evolución microestructural en aleaciones cu-ni-fe envejecidas isotermicamente

Se realizó la simulación numérica de la evolución microestructural en aleaciones Cu-Ni-Fe, Cu-48%at.Ni-8%at.Fe y Cu-46%at.Ni-4%at.Fe envejecidas a 673, 723 y 773 K por diferentes tiempos. Se siguió la evolución microestructural utilizando MICE, MET y DRX para las aleaciones Cu-48%at.Ni-8%at.Fe y Cu- 46%at.Ni-4%at.Fe envejecidas a las mismas condiciones. Los resultados de simulación numérica mostraron una buena concordancia con los experimentales. La descomposición de fases ocurre en forma espinodal produciendo dos fases: rica en Cu-Ni y rica en Ni-Fe. La morfología y composición de las fasescoinciden con las observadas experimentalmente y/o reportadas en la literatur

Numerical and Experimental Analyses of the Effect of Heat Treatments on the Phase Stability of Inconel 792

A study about the precipitation and phase stability was carried out in an IN-792 superalloy used as a blade in a gas turbine. Microstructure analysis was conducted experimentally on three different cross sections of the blade designated as high temperature (HT), medium temperature (MT), and low temperature (LT). To identify the HT, MT, and LT sections, a numerical thermal analysis was performed using ANSYS software. To obtain the distribution gradient of temperature in the blade, the real conditions of operation in steady state of the gas turbine were considered. A numerical study about the occurrence of phases in the IN-792 superalloy was carried out with Thermo-Calc and TC-PRISMA software. The analysis of the as-cast IN-792 superalloy with Scheil-Gulliver equations permitted to explain the phase formation during the solidification process. The calculated time-temperature-precipitation (TTP) diagram explains consistently the precipitation process observed after two different heat treatment conditions applied experimentally and numerically to regenerate the original microstructure of the IN-792 superalloy. The experimental results were consistent with the calculated isoplethic and TTP diagrams. In terms of accuracy, the further development of the Thermo-Calc databases for thermodynamic calculations in superalloys is evident. It was possible to calculate precipitation temperatures and the local evolution of precipitated particles for two different heat treatment conditions