Microstructure and mechanical properties of WMoTaNbTi refractory high-entropy alloys fabricated by selective electron beam melting

WMoTaNbTi RHEAs formed by SEBM with negative defocus distance were investigated. Four scanning speeds were applied, an electron beam with scanning speed at 2.5 m/s completely fused the premixed WMoTaNb alloyed powder and pure Ti powder. Significant vaporization of Nb and Ti elements happened during the formation of WMoTaNbTi RHEAs, however, the single BCC phase remains stable. Weakened solid-solute strengthening caused by elemental vaporization, dropping percentage of Nb and Ti solutes in the matrix as well as improved ductilizing effects with decreasing scanning speeds leads to falling microhardness and better local ductility. Microhardness of scanning speed at 4.0 m/s, 3.5 m/s, 3.0 m/s and 2.5 m/s is 578 +/- 17 HV, 576 +/- 12 HV, 573 +/- 10 HV and 511 +/- 2 HV, respectively. The as-deposited WMoTaNbTi RHEA formed at a scanning speed of 2.5 m/s displays ultimate strength of 1312 MPa. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

WMoTaNbTi RHEAs formed by SEBM with negative defocus distance were studied. The results show that the decrease in scanning speed leads to vaporization of Nb and Ti elements, weakening the solid-solute strengthening and reducing the content of Nb and Ti solutes in the matrix, resulting in improved ductility and decreased microhardness. The as-deposited WMoTaNbTi RHEA formed at a scanning speed of 2.5 m/s exhibits high ultimate strength.