Low-pressure forming and reactive sintering for the synthesis of equimolar CoCrFeNi bulk alloys

This work presents a binder-aided process that enables uniaxial pressing of fine metal powders in the low-pressure regime of the compressibility curve, yielding consolidated alloys after debinding and pressureless sintering. Unlike traditional powder metallurgy, where applied loads exceed the powder yield stress, the proposed method relies on powder rearrangement and cohesion made possible by a lubricant/binder. Equimolar CoCrFeNi alloys are synthesized using this strategy with stearic acid serving as lubricant/binder. Reactive sintering is carried out at 1200 °C, resulting in the formation of a single-phase face-centered cubic (FCC) CoCrFeNi alloy. Particular attention is given to the lubricant/binder admixing procedure (solvent-aided or mechanical mixing) and its influence on powder characteristics, compaction behavior, and the resulting microstructure. Lubricant distribution is evaluated by laser diffraction and elemental mapping, while density and porosity are evaluated using established methods and phase composition is determined by X-ray diffraction. It is shown that reactive fine powders admixed with stearic acid using a solvent-aided route lead to a more uniform additive distribution and more effective debinding compared to mechanical mixing, while resulting in lower densification, with relative densities up to ~ 0.9. The proposed approach is particularly relevant for applications such as sputtering targets for physical vapor deposition (PVD), where full densification is not critical for their performance.