Formation of Laves Phase and Its Effect on Microstructure and Mechanical Properties of Ti₈Zr₆Nb₄V₅Cr_x Lightweight High‐Entropy Alloys

To investigate effects of Cr on mechanical properties of lightweight high‐entropy alloys (LHEA) and enhance mechanical properties of alloys, Ti₈Zr₆Nb₄V₅Cr_x LHEAs are prepared by vacuum nonconsumable arc melting. Effects of Cr on phase constitution, microstructure characteristics, and mechanical properties of LHEAs are investigated. In the results, it is shown that addition of Cr into Ti₈Zr₆Nb₄V₅ LHEAs leads to phase transition from body‐centered cubic (BCC)2 to C15 Laves. Dimensional size of BCC phase first increases and then decreases while volume fraction of C15 Laves phase shows opposite trend with increasing of Cr. Phases are greatly refined when Cr content is 4 at%, and average grain size of LW‐Cr4 alloy is the smallest of 10.7 μm. Moreover, density of alloys increases slightly and strength of the alloys increases significantly by adding varying Cr content. Compressive strength and yield strength of alloys show first increase and then decrease with addition of Cr, and those of LW‐Cr2 alloy reach maximum of 2326.3 and 2046.1 MPa, respectively. LW‐Cr1 alloy shows excellent comprehensive mechanical properties with compressive strength of 1963.8 MPa and fracture strain of 23.5%. Strengthening of the alloy is directly related to increase of BCC phase, precipitation of high‐strength C15 Laves phase, and solid‐solution strengthening of Cr atoms.