Synthesis of FeCrCoNiCu high entropy alloy through mechanical alloying and spark plasma sintering processes

Abstract

FeCrCoNiCu high entropy alloy (HEA) was produced through mechanical alloying (MA) and spark plasma sintering (SPS) processes. Using X-Ray diffraction, scanning electron microscopy, differential scanning calorimetry, and shear punch testing, the structural, microstructural, and mechanical properties of the milled and SPSed samples were evaluated. After 50 h of milling, a dual-phase solid solution HEA formed consisting of a major FCC phase and a minor BCC phase. Increasing milling time and repeated deformation of the powders led to increased strain and dislocation density, and eventually, an alloy with a uniform distribution of particles with reduced size was achieved. Sintering of the alloy at 750 °C resulted in the annihilation of the BCC phase and the formation of a sigma phase. Moreover, segregation of the elements due to the different mixing enthalpies led to the formation of a new FCC phase. Results revealed that the SPSed alloy that was properly sintered had a porosity of less than 8%, which resulted in good final mechanical properties such as ultimate shear strength of 300 MPa and ultimate tensile strength of 540 MPa.