Abstract
Biphase eutectic high entropy alloy AlCoCrFeNi2.1 composites reinforced with WC particles were prepared by an innovative fast hot pressing sintering (FHPS) method. The microstructure and mechanical properties of the sintered high entropy alloys were investigated. Result shows that neck discharge is formed under the action of electrical current, and material densification is realized due to Joule heating and electromigration effect. BCC phase was found to coexist with the primary FCC phase in the matrix. This biphase formation process in the matrix is extensively investigated. Based on Gibbs free energy change calculation, energy spectrum analysis and diffraction specks, the reaction layer was found to be made of chromium carbide. The sintered high entropy alloys obtained high hardness (491.9HV) and good strength (972.9 MPa) due to the combined strengthening mechanisms during sintering. Dislocation strengthening and solution strengthening are found to be the main strengthening mechanisms. As the sintering temperature increases, the ductility of the sintered high entropy alloy increases, but its strength decreases slightly due to the growth of grain. The biphase fracture of the matrix and the breakage and detachment of the reinforcement particles were also noticed to coexist on the fractured surface.
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