Hot forming behavior of ni-base superalloys and their modeling

Resumen

Numerical and experimental simulation of engineering materials has been an emerging topic for recent decades. Reliable and efficient numerical simulations are only possible through correct and pragmatic modeling approaches. This Ph.D. work is focused on understanding and modeling the hot forming behavior of polycrystalline superalloys. In other words, this is an attempt to comprehend and model the deformation characteristics and microstructural evolution of these alloys during hot forming. Understanding the hot forming behavior of such alloys is of interest from an industrial perspective due to the fact that the service performance is highly dependent on the final microstructure, while the final microstructure is affected by many processing parameters, such as solutionizing time/temperature, deformation rate/temperature or existence and length of dwell time between processing steps. Within the scope of the current work, a recently developed Allvac 718Plus is studied. The first part of this text addresses the modeling of flow curves obtained through uniaxial hot compression tests at different temperatures and strain rates. The second part is dedicated to the multiscale characterization of the precipitation behavior and the dislocation precipitation interaction in Allvac 718Plus. Apart from uniaxial hot compression tests, stress relaxation tests and various characterization methods such as optical, scanning and transmission electron microscopy are implemented. Understanding the hot forming behavior of such alloys is of interest from an industrial perspective due to the fact that the service performance is highly dependent on the final microstructure, while the final microstructure is affected by many processing parameters, such as solutionizing time/temperature, deformation rate/temperature or existence and length of dwell time between processing steps. Within the scope of the current work, a recently developed Allvac 718Plus is studied. The first part of this text addresses the modeling of flow curves obtained through uniaxial hot compression tests at different temperatures and strain rates. The second part is dedicated to the multiscale characterization of the precipitation behavior and the dislocation precipitation interaction in Allvac 718Plus. Apart from uniaxial hot compression tests, stress relaxation tests and various characterization methods such as optical, scanning and transmission electron microscopy are implemented.