Effect of Ho additions on the microstructure and mechanical properties of Nb-22Ti-16Si-7Cr-3Al-3Ta-2Hf alloys

Abstract

Abstract The effect of Ho additions on the microstructure and compressive properties of the alloy Nb-22Ti-16Si-7Cr-3Al-3Ta-2Hf (at.%) was investigated by using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and by performing compression tests. The results show that Ho additions cause remarkable microstructural refinement. The addition of 0.1 at.% Ho to the alloy increases its strength and ductility. When the amount of Ho is increased to 0.2 at.%, the strength and ductility decreases. Ho addition inhibits the formation of the (Ti, Nb)5Si3 phase and the amount of the (Ti, Nb)5Si3 phase decreases, even disappears, with increasing Ho content. In addition, the fracture surfaces of Ho-free alloys deformed at room temperature in compression tests exhibit cleavage for both the (Nb, Ti) solid solution and the (Nb, Ti)5Si3 intermetallic compound, while limited local plastic strain of the (Nb, Ti) solid solution is observed in Ho-doped alloys. The effect and mechanism of strengthening and plastic deformation of Ho additions to the alloy was discussed in view of the microstructure.