Synergistic Optimization of Microstructure and Mechanical Properties of Zr-based Eutectic Alloy

Abstract:

Based on eutectic alloy design strategies combined with Pandat thermodynamic calculations, Zr_x(NiFe)_100-x (x=75, 83, 90, wt%) alloy systems were designed and prepared. Furthermore, the intrinsic correlation mechanism between the microstructure and mechanical properties of the alloys was investigated. Results show that at Zr concentrations of 83wt% and above, the alloys exhibit a distinctive lamellar eutectic microstructure (tI12-Zr₂(Ni/Fe)/fcc-Zr) coexisting with hcp-Zr, featuring nanoscale FeZr₃ interphase precipitates at eutectic interfaces. Notably, the liquidus formation temperature exhibits a substantial reduction to approximately 974 ℃. The Zr₈₃(NiFe)₁₇ and Zr₉₀(NiFe)₁₀ alloys exhibit compressive strengths of 1352±12 and 1263±10 MPa with corresponding fracture strains of 14.2%±0.4% and 17.0%±0.3%, respectively. These values represent a significant enhancement in fracture strain compared to conventional Zr-based amorphous alloys while maintaining comparable strength properties. Fractographic analysis reveals that dislocation pinning and shear band bifurcation phenomena induced by eutectic interfaces effectively impede crack propagation, facilitating a transition in fracture mode from brittle cleavage to 45° shear-dominated failure with increasing Zr content. Under dynamic compression, both Zr₈₃(NiFe)₁₇ and Zr₉₀(NiFe)₁₀ alloys exhibit a strain rate hardening effect, and when the strain rate exceeds a critical value, the alloys undergo a ductile-to-brittle transition.