Effect of diffusion saturation with oxygen on the surface-layer structure and mechanical properties of niobium alloys

1. The interaction of niobium alloy 5VMTs, with oxygen within the temperature range 600–900°C changes ambiguously with increasing temperature and takes place with the preferential formation of excess-phase particles in the surface layers at 600 and 900°C, while deep and intensive saturation without the formation of oxides occurs at 800°C. 2. Saturation of the surface layer to a depth comprising 2–6% of the cross section significantly reduces the ductility, and at greater depths, results in the embrittlement of niobium alloys 5VMTs and Nb-1Zr. 3. The oxides formed during saturation in a recrystallized material are localized along grain boundaries, disturbing the cohesion between grains. 4. Saturation of cold-worked material with oxygen delays recrystallization and results in uniform precipitation of an excess phase with subsequent high-temperature heating.