Effect of carbon on the tensile properties of Nb-Mo-W alloys at 1773 K

Ternary Nb-Mo-W alloys of various composition and carbon and oxygen contents were prepared to investigate the deformation and fracture behavior by tensile and compression tests at 1773 K. The fracture mode changes from transgranular to intergranular with increasing molybdenum and tungsten contents as substitutional elements of the VIA group, and with increasing oxygen content. A certain amount of carbon addition to Nb-5Mo-15W alloy causes niobium carbide (Nb2C) precipitation along grain boundaries and improves the ductility accompanied by a change in the fracture mode. It is suggested that carbide precipitation and carbon segregation at grain boundaries are responsible for the ductility improvement in carbon-doped Nb-5Mo-15W alloys. (C) 2002 Elsevier Science B.V. All rights reserved.