The Laves phase formation in rapidly quenched Zr-Al-Ni-Co-Cu high-entropy alloy

Abstract

Multicomponent alloys containing aluminum and transition metals, including high-entropy alloys, are actively investigated in recent years. Rapid quenching of melt to obtain metastable or amorphous phases is a promising way to obtain new strength and corrosion resistance high-entropy materials. In present work, the effect of rapid quenching on the phase formation process of high entropy Zr-Al-Ni-Co-Cu alloy is investigated. Samples of Zr₄₀Al₂₀Ni₅Co₁₅Cu₂₀ alloy were produced by the conventional arc-melting process under protective argon atmosphere. Ingots of the alloy were used to obtain rapidly quenched samples in the form of cylindrical rods with a diameter of 3 mm by vacuum suction casting into copper mold. Structure of ingots and rods was investigated by X-ray diffraction and scanning electron microscopy, their heating behavior was studied by differential scanning calorimetry. It is shown that the basis of the rapidly quenched alloy is the Laves phase ZrCoAl, the solid solution Cu_0.6ZrCo_0.4 and the ZrNiAl phase. Exothermic reaction in rapidly quenched sample is found to occur at 960–980 K. Activation energy of the detected reaction is calculated by the Kissinger method. It is established that rapid quenching of Zr₄₀Al₂₀Ni₅Co₁₅Cu₂₀ high-entropy alloy leads to significant refinement of Laves phase grains, increase of stability and volume fraction of solid solution. The obtained results can be used for further practical application of rapidly quenched high-entropy alloys.