Production and Characterization of Precipitation Hardenable HEAs Designed by High perfomance Thermodynamic Calculations

Abstract

Multicomponent alloys or high entropy alloys (HEA´s) are a group of metallic alloys that exhibit the characteristic of not having a principal element but instead are made of concentrated solid solutions. Among the applications of interest for multicomponent alloys there is the use of this kind of material in high temperatures, for example in engines and motors. Having this in mind, it´s very important to study multicomponent alloys which have FCC crystal structure and can exhibit precipitation hardening, especially the case that the precipitates have L12 Crystal structure. This kind of precipitate is very coherent with the FCC matrix and has good thermic stability what makes the HEA´s that can have FCC/L12 precipitation hardening promising considering high temperature applications. In the present work, there will be used high performance thermodynamic calculations (CALPAD method) in great compositional fields, together with mathematical models aiming to calculate the ani-phase boundary energy and to estimate/calculate the precipitation hardening component of multicomponent alloys containing Cr, Fe, Al, Ti, Ni e Co at different proportions, what will generate important information's about age hardening capacities for these alloys. During the execution of the present project there will be chosen compositions among those analyzed by the CALPHAD method and there will be produced specimens that will undergo different combinations of time and temperature heat treatments aiming to study the precipitation effects more deeply in these compositions. The specimens will also be analyzed by techniques like Scanning and transmission electron microscopy, DSC, micro hardness, and nano hardness. One of the compositions will be chosen and there will be produced ingots that will be cold rolled and homogenized. These ingots will be used to produce specimens for tensile tests in the aged and solubilized conditions. The set of employed techniques will allow an evaluation regarding the precipitation effects in the analyzed multicomponent alloys.