A comparison study on microstructures and fracture behaviours of a single NbSS solid solution alloy and a two-phase NbSS/Nb5Si3 alloy prepared by spark plasma sintering and arc melting

Abstract

Single NbSS phase alloy (Nb-37Ti-13Cr-2Al-1Si) and two-phase NbSS/Nb5Si3 alloy (hypoeutectic composition of Nb-16Si-24Ti-2Al-2Cr) powders prepared by the plasma rotating electrode atomization technique (PREA) were spark plasma sintered (SPS), and the microstructure, fracture toughness, deformation and fracture mode of the two SPS and arc melting (AM) alloys were characterized. With a coarsened grain size, the AM and SPS single NbSS phase alloy had a small difference in fracture toughness and it failed in a cleavage mode. As for the SPS two-phase NbSS/Nb5Si3 sample containing an ultra-fine ductile/stiffening NbSS/Nb5Si3 microstructure, approximately 1–2 μm in phase size, a fracture toughness of as high as 16.1 MPa·m1/2 was obtained, owing to operation of the active dislocation of a/2 〈111〉 and dimple failure of the fine NbSS phase. However, the AM two-phase NbSS/Nb5Si3 microstructure had a coarsened NbSS phase and a low fracture toughness of 9.6 MPa·m1/2, resulting from the movement of a 〈100〉 dislocation in the {001} cleavage planes and a cleavage failure mode of the coarsened NbSS phase.