Effects of hf on mechanical properties of Nb-15W-5Si-2B alloy at room-temperature and high-temperature

To probe balance between room-temperature plasticity and high-temperature strength of Nb-Si based alloys, Nb-15W-5Si-2B-xHf (x = 0, 5, 10, 15 at%) alloys with an Nb_SS-dominant microstructure were developed, and the effects of Hf addition on the microstructure and mechanical properties of Nb-5Si-15W-2B-xHf at room-temperature and high-temperature were investigated and compared. The results show that the microstructure of the Nb-15W-5Si-2B is composed of the Nb_SS matrix and the network Nb₅Si₃; the Hf addition does not change the phase constitution, however, with an Hf addition the morphology of the Nh₅Si₃ phase becomes islands gradually and the Nb₅Si₃ fraction decreases. Both the high-temperature compression strength and the room-temperature plasticity of the Nb-15W-5Si-2B alloy are improved by the Hf addition at the same time. However, Hf is harmful for creep behavior at high-temperature. Finally, the strengthening and ductilizating mechanisms of Hf on the Nb-15W-5Si-2B alloy are primarily discussed.