Effect of C, N and B addition on the phase equilibrium and mechanical behavior of the Cr40Co40Ni20 multi-principal element alloy

Abstract

Multi-principal element alloys (MPEAs), complex and concentrated alloys, and medium and/or high entropy, are names of a new class of materials which main characteristic is not having a main element. Recent literature works points out the need to explore more complex routes and mechanisms for microstructural development in alloys that already have promising potential. An important refining route still in development for these alloys is the use of interstitial elements to control phase transformations and grain growth. Recent studies developed by the DEMa/UFSCar research group, including the current proponent's master's thesis, show the high potential of Cr-Co-Ni alloys, especially high Cr alloys. This system, widely studied in the literature, include alloys with excellent mechanical properties under tension, a prominent alloy is Cr40Co40Ni20, developed and studied during the proponent's master's degree, which has good mechanical properties, among which we can highlight: ) a high intrinsic yield strength, resulting from solid solution strengthening, (2) high potential for increasing mechanical strength via grain refining and (3) TWIP and TRIP effects very active during deformation. Thus, the objective of this thesis is to study the effect of C, N and B additions on the phase equilibria, grain refining and mechanical behavior of the Cr40Co40Ni20 MPEA. For this purpose, additions of C, N and B capable of generating microstructural refining effects will be selected through thermodynamic calculations. The compositions will be produced and their phase stability and mechanical behavior will be investigated. This study will help to elucidate the real potential of multicomponent alloys of the much studied Cr-Co-Ni system, but now refined using promising microstructural refining routes for other multicomponent alloys in the literature. (AU)