Creep of niobium and solid solution strengthened Nb-1wt.%Zr

Abstract

The search for new materials for advanced aerospace structural applications at elevated temperatures has renewed an interest in niobium and its alloys due to its high melting point (2741 K), low thermal neutron cross section, good corrosion resistance against liquid lithium, and low density (8. 58 gm/cc) compared to other refractory metals. However, the diffusivity of bcc niobium is high and, as a result, the creep strength of niobium is inherently weak. Solid solution strengthening is one approach to improve the creep strength of metallic materials. Solid solution strengthening of class M (pure metal type) materials changes the creep response and rate controlling deformation mechanism. Class M materials show a normal transient during the primary stage in a semilogarithmic plot of [dot [Epsilon]] versus [Epsilon] and the rate controlling mechanism is dislocation climb. Class A (alloy type) materials show an inverse transient during the primary stage in a [dot [Epsilon]] versus [Epsilon] semilogarithmic plot, and the rate controlling mechanism is viscous glide. The objective of this paper is to study and compare the creep behavior of niobium and Nb-1wt. %Zr.