A Design of TiZr-rich Body-centered Cubic Structured Multi-principal Element Alloys with Outstanding Tensile Strength and Ductility

Abstract Body-centered cubic (BCC) multi-principal element alloys (MPEAs) have drawn extensive attention for their interesting structures and good mechanical properties. However, most BCC MPEAs lack ductility at room temperature. Decreasing the valence electron concentration (VEC) value is an effective approach to design the BCC MPEAs with intrinsic ductility. Three TiZr-rich MPEAs (Ti45Zr45Nb5Ta5, Ti45Zr45Nb5Mo5, and Ti42.5Zr42.5Nb5Mo5Ta5) were designed in this paper, by controlling their VEC through restricting the contents of group V (Nb, Ta) and group VI (Mo) elements into 5 at.%. These alloys all possessed BCC structure, low elastic modulus (56∼74 GPa), and intrinsic ductility in the as-cast status. Among the three MPEAs, Ti42.5Zr42.5Nb5Mo5Ta5 exhibited a finer microstructure, as well as higher tensile yield strength (∼907 MPa) and elongation (∼14.9%). The theoretical calculation indicates that the high strength of Ti42.5Zr42.5Nb5Mo5Ta5 alloy mainly was attributed to solid solution strengthening. The results also show that Mo element possesses a stronger solution strengthening effect than Ta, as it has a wide difference of shear modulus compared to the other constituent elements.