Influence of Nb on the Microstructure and Fracture Toughness of (Zr(0.76)Fe(0.24))(100−x)Nb(x) Nano-Eutectic Composites

The present study demonstrates the evolution of eutectic microstructure in arc-melted (Zr(0.76)Fe(0.24))(100−x)Nb(x) (0 ≤ x ≤ 10 atom %) composites containing α-Zr//FeZr(2) nano-lamellae phases along with pro-eutectic Zr-rich intermetallic phase. The effects of Nb addition on the microstructural evolution and mechanical properties under compression, bulk hardness, elastic modulus, and indentation fracture toughness (IFT) were investigated. The Zr–Fe–(Nb) eutectic composites (ECs) exhibited excellent fracture strength up to ~1800 MPa. Microstructural characterization revealed that the addition of Nb promotes the formation of intermetallic Zr(54)Fe(37)Nb(9). The IFT (K(IC)) increases from 3.0 ± 0.5 MPa√m (x = 0) to 4.7 ± 1.0 MPa√m (x = 2) at 49 N, which even further increases from 5.1 ± 0.5 MPa√m (x = 0) and up to 5.9 ± 1.0 MPa√m (x = 2) at higher loads. The results suggest that mutual interaction between nano-lamellar α-Zr//FeZr(2) phases is responsible for enhanced fracture resistance and high fracture strength.