The Effect of Nitrogen on the Tensile and Creep-Rupture Properties of Niobium
NAVAL RESEARCH LAB WASHINGTON DC
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Variations in the mechanical properties of niobium caused by nitrogen additions in amounts to give single-phase and two-phase structures were investigated at both room and high temperatures. Nitrogen in solid solution raised room-temperature hardness and tensile strength. Increasing the nitrogen content to give two-phase structures however produced no additional strengthening. At elevated temperatures, the effect was different in that, with increase in nitrogen content, there was a continued rise in tensile strength through the two-phase region. Creep-rupture strength of niobium was improved by nitrogen in solution at temperatures slightly below 0.5 times the melting temperature, whereas above this temperature the strength was unaffected. This change in the nitrogen effect with temperature appears to be related to a concurrent change in the mechanism controlling creep. An increase in the nitrogen content of the two-phase alloys produced strengthening throughout the 1700 to 2600F test range. Ductility was high for all alloys at elevated temperatures and, except for a high-nitrogen alloy, also at room temperature.
- Properties of Metals and Alloys