Tensile creep behavior of the Nb45Ta25Ti15Hf15 refractory high entropy alloy

• DOI: 10.1016/j.actamat.2024.119940
• Publication Date: 2024-04-21T03:26:17Z
• Authors: Gianmarco Sahraga...; Calvin H. Belcher; Sakshi Bajpai; Mark Wirth; Arun Devaraj; Diran Apelian; Enrique J. Lavernia; Robert O. Ritchie; Andrew M. Minor; Jeffery C. Gibeling; Cheng Zhang; Mingwei Zhang
• Keywords: Embrittlement; Ductility (Earth science); Brittleness; Diffusion creep

The tensile creep behavior of a vacuum arc-melted Nb45Ta25Ti15Hf15 refractory high entropy alloy was investigated over constant true stress range 50-300 MPa at temperature 1173 K. Creep tests were carried out in both (5×10−6 torr) and ultrahigh purity Ar gas to examine the environmental effect. samples tested exhibited power law with exponent 4.1 exceptional ductility, whereas those suffered significant embrittlement due HfO2 formation grain boundaries, which exacerbated low applied stresses where extended exposure residual O2 resulted more extensive brittle intergranular fracture. Phase decomposition occurred after long-term thermal exposure, second Hf-rich body-centered cubic phase formed predominantly boundaries but did not cause embrittlement. Compared equiatomic TaNbHfZrTi (Senkov alloy) face-centered multiple-principal element alloys, has superior resistance, especially stresses, while maintaining excellent ductility. Transmission electron microscopy revealed that deformation K is controlled by cross-kink collisions from screw dislocations results dipole drag lower strain rates jog higher rates.