Oxidation and its effects on the mechanical properties of Nb-1Zr

The alloy Nb-1Zr is a high temperature material that is often considered fo r applications where strength and resistance to alkali metals are required. However, these favorable properties can be compromised because it lacks ox idation resistance in many environments. After reviewing the oxidation beha vior of Nb-1Zr, additional studies were conducted in high temperature, low pressure gaseous oxygen environments to determine the effects of oxidation on the tensile properties and hardness of Nb-1Zr for a specific space syste m application. Strengthening and loss of ductility were found to occur from room temperature to 900 degreesC following low pressure oxidation in vacuu m or argon at 750 degreesC and 900 degreesC, respectively. In general, oxyg en that is associated with zirconium as extremely fine zirconium-oxygen zon es is responsible for the strengthening/embrittlement that is observed. Hea t treatments that result in non-coherent ZrO2 precipitates can neutralize t he effects of oxygen on mechanical properties provided the total oxygen con tent is below that required to convert all of the Zr to oxide. (C) 2001 Pub lished by Elsevier Science B.V.