Abstract
New High Entropy Alloys based on the CoCrFe2Ni2 system have been developed by adding up to 10 at. % of Cu, Mo, and Cu + Mo in different amounts. These alloys showed a single face-centred cubic (FCC) structure after homogenization at 1200 °C. In order to evaluate their thermal stability, aging heat treatments at 500, 700, and 900 °C for 8 h were applied to study the possible precipitation phenomena. In the alloys where only Cu or Mo was added, we found the precipitation of an FCC Cu-rich phase or the µ phase rich in Mo, respectively, in agreement with some of the results previously shown in the literature. Nevertheless, we have observed that when both elements are present, Cu precipitation does not occur, and the formation of the Mo-rich phase is inhibited (or delayed). This is a surprising result as Cu and Mo have a positive enthalpy of mixing, being immiscible in a binary system, while added together they improve the stability of this system and maintain a single FCC crystal structure from medium to high temperatures
Highlights
The CoCrFeNi system has been extensively studied in the HEA (High Entropy Alloy) scientific community, and it is the base composition of a large number of multicomponent alloys or compositionally complex multi-principal alloys, depending on the nomenclature employed
Showed single face-centred cubic (FCC) structures without the presence of secondary phases, from which one can conclude that all the compositions are High Entropy Alloys
Secondary phases or precipitation phenomena may occur at medium temperatures and a fast screening is performed with dilatometry, from which some reference temperatures are selected to apply the thermal treatments and promote such potential precipitation
Summary
The CoCrFeNi system has been extensively studied in the HEA (High Entropy Alloy) scientific community, and it is the base composition of a large number of multicomponent alloys or compositionally complex multi-principal alloys, depending on the nomenclature employed. Cu segregates, forming Cu-rich precipitates in this system [11,19,20,21] and others, such as in the AlCoCrFeNi + Cu [22,23,24], the AlCoCrFeNiTi + Cu [25], or the AlCoNiTiZn + Cu [26] families This highlights the inclination of this element to elemental separation, which occurs especially at the grain boundaries, often inducing a detrimental effect into the mechanical properties or even into the microstructural stability due to the matrix compositional variations. We observed that Mo precipitation occurs for the Cu-free alloys, which, are impeded in the presence of Cu
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
