Microstructural refining mechanisms and mechanical properties optimization in high toughness multi-principal element alloys

Abstract

Multi-Principal Element Alloys (MPEAs) are metallic alloys that do not have a single main element which yields an immense number of possible compositions. Despite this, several alloys with interesting sets of properties have already been found. The featured compositions include those of the Cr-Co-Ni system, which are among the toughest materials ever developed, which can be attributed to the various strengthening and deformation mechanisms active in this material when mechanically deformed. The objective of the present project is to optimize the mechanical properties of the Cr-Co-Ni system alloys already identified as promising in previous work by the proponent. This search for optimization will take place on three different fronts: (1) Additions of substitutional elements capable of increasing the intrinsic mechanical strength of the alloy, (2) search for effective interstitial elements effective in microstructural refining via reduction of recrystallization and grain growth kinetics and (3) incorporation of a precipitation hardening mechanism by fine, dispersed and ordered phases with high resistance to dislocation shearing. An initial step will be dedicated to the design of alloys using a combination of different computational methods. The alloys will then be produced and characterized by different techniques. The most promising compositions will be subjected to mechanical tests of tension and impact to evaluate the mechanical properties under different loading conditions. Deformed samples will also be characterized to correlate the deformation mechanisms operating in these alloys with their mechanical properties. (AU)