Simultaneous improvement in strength and ductility of 3D-printed refractory high-entropy alloys by addition of molybdenum

Molybdenum (Mo) is an important strengthening element in refractory high-entropy alloys. However, it is difficult to produce a Mo containing alloy with uniform elemental distribution because of the high melting point of Mo. This work employed 3D printing, also known as laser additive manufacturing (LAM), technique to prepare TiZrVNbAl-system refractory high-entropy alloys (RHEAs) with different Mo contents. Due to the high temperature and strong convection in melting pool, uniform elemental distribution is achieved in LAM TiZrVNbAl-system RHEAs. With increasing Mo, the solid-liquid intervals of alloys increase, which promotes the formation of fine equiaxed growth, and reducing in the mean grain sizes. Meanwhile, a large difference in the atomic radius between the Mo and the TiZrVNbAl RHEA results in strong solid-solution strengthening, and hence a 34 % increase in the yield strength. These results imply that the LAM is a promising technique to produce RHEAs with uniform elemental distribution, as well as good strength−ductility balance, which is expected to be able to widen the potential applications these refractory alloys.