Achieving High Damping Capacity in Oxygen-Enhanced BCC Zr-Hf-Ti-Nb Multi-Principal-Element Alloys with Low Young's Modulus.

Multi-principal-element alloys (MPEAs) have gained widespread popularity due to the efficient synergetic regulation of mechanical and functional properties in a huge compositional space. Here, novel O-enhanced BCC Zr-Hf-Ti-Nb MPEAs with prominent mechanical and damping properties are developed by the composition formula of (Zr,Hf,Ti)Nb. The ZrTiNb and ZrHfTiNb alloys possess low BCC-β structural stability. While the ZrHfTiNb alloy has a much higher BCC-β stability, as evidenced by the fact that only few α'' and ω precipitates appear in 1.8 at% oxygen-added alloy. This alloy exhibits an optimal mechanical property with a higher yield strength (σ = 1000 MPa) and larger ductility (ε = 15.1%), which is ascribed to the formation of O-rich clusters in BCC matrix. Moreover, these oxygen-free and -added alloys exhibit an excellent damping capacity due to their low Young's modulus (E < 70 GPa), as exemplified with a peak value of (tanδ) = 0.02 for 1.8 at% oxygen-added alloy. Notably, the damping characteristics are prominent over a wide temperature range (550-800 K), which derives from the occurrence of multiple separated oxygen-rich clusters. The present findings provide an avenue to enhance mechanical and functional performances of high-temperature damping alloys.