Effect of internal oxidation on the microstructure and mechanical properties of C-103 alloy

The effect of internal oxidation on the microstructure and mechanical properties of niobium alloy, C-103 has been investigated. Tensile specimens and test coupons of alloy containing different levels of oxygen (100-2500 ppm) were characterized with respect to microstructure and mechanical properties. It has been observed that for oxygen contents in the range ∼400-1000 ppm, hafnium oxide precipitated exclusively along the grain boundaries, while for oxygen content of ∼2500 ppm, precipitates formed both at the grain boundaries and within the grains near surface region of the alloy. The internal oxidation has resulted in embrittlement of the alloy resulting in considerable lowering of strength as well as ductility. Further, the strength and ductility are found to decrease progressively with the increase in average oxygen content of the alloy.