AlCoCrFeNix (x = 0, 1, 2.1) HEA particle hardness determination using nanoindentation

Particulate feedstock is an inherent process need for modern-day additive manufacturing technologies such as high-pressure cold spray (HPCS). The developed modules, whether they are 2D/3D coatings, 3D/4D architectured components, or additively repaired/re-engineered devices, are only competitive as long as their underlying feedstock qualities are met. This research presents recent progress in devising a needed technique to understand the nanoscale hardness of particles representing an emergent class of alloys, the high-entropy alloy (HEA). The feasibility of determining AlCoCrFeNi_x (x = 0.1, 1, 2.1) HEA particle hardness without post-processing using the nanoindentation technique was explored. In doing so, the evolution of mechanical properties of the mechanically-alloyed AlCoCrFeNi_x particles, along with their milling times (4 hours to 24 hours) and progressive Ni atomic ratio (x = 0, 1, 2.1) variation, is presented. Particles were metallographically prepared per ASTM E3 standard, and their nanoscale hardness and elastic modulus were determined using a Nanoindenter equipped with a Berkovich tip. The effect of pre-determined maximum load and indentation depth on the hardness values was analyzed, giving a pathway for embracing the method for similar tests/characterization in an array of materials.