High entropy alloys are complex alloying elements that possess exceptional mechanical properties compared to conventional alloys such as steels. In order to bulk produce components for structural applications using these alloys, processes involving high temperature such as hot rolling, forging, or extrusion are conducted. These impose a large strain in a single operation. Also, the processes should not induce the onset of failures such as cracks or fractures in the material.
“Therefore, careful optimization of processing parameters is of vital importance since they may have a significant influence on the deformation mechanisms, microstructural evolution, and final mechanical properties of the produced alloy structures,” says Madan Patnamsetty.
Hot deformation parameters are physical parameters that impact the microstructural features of a material like strain rate, strain and temperature. Studying and modelling these parameters can help predict the safe workable domains that can be used while the material undergoes various industrial processes for production in structural applications.
There exists only limited information about the hot workability of HEAs and their respective deformation mechanisms. In his current work, Patnamsetty studied the influence of hot deformation parameters, consequent structural evolution, and associated deformation mechanisms of two selected HEAs (CoCrFeMnNi and Al0.3CoCrFeNi) intended for advanced engineering and structural applications.
The constitutive model can be used to in Finite Element Analysis to simulate the hot deformation conditions of the two HEAs. Also, they can predict the load required for deformation of the HEAs to a certain reduction at a constant temperature and strain rate. These inputs are used in the industry to produce bulk components like sheets, bars etc.
“The processing maps helped to identify the ‘safe’ hot working domains of HEAs for realizing defect-free microstructures,” he adds.
Madan Patnamsetty currently works for Elcogen Oy to select materials and coatings depending on their high temperature mechanical and corrosion properties intended for solid oxide fuel cell application.
The doctoral dissertation of MSc (Tech) Madan Patnamsetty in the field of Material Science and Engineering titled Constitutive Modelling, Processing Maps and Dynamic Restoration Behavior of High Entropy Alloys will be publicly examined in the Faculty of Engineering and Natural Sciences at Tampere University on Friday 16 December at 12 at Hervanta Campus in the lecture hall K1702 of the Konetalo building (Korkeakoulunkatu 6, Tampere). Prof. Sheng Guo from the Chalmers University of Technology, Sweden, and Dr. Alexander Kauffmann from Karlsruhe University of Technology, Germany will act as opponents. Prof. Pasi Peura from Tampere University will serve as the Custos.
The doctoral dissertation is available online.
Photo: Jukka Göös