Investigation of a High-Temperature Nb-Based Composite Material Mechanically Doped with Si

Resumo

Abstract—The influence of Si and uncontrolled interstitial impurities (oxygen and carbon) in trace amounts on the strength characteristics of a high-temperature composite material (HCM) based on Nb obtained by the powder metallurgy technique has been studied. It has been established that the bending strength of specimens manufactured by mechanical homogenization and mechanical alloying exceeds the strength of a material obtained from an original niobium powder by a factor of 3–4.5, with the main contribution to the increase in strength being made by mechanical homogenization of the original niobium. Optimal HCM properties were obtained during alloying of the Nb powder in a planetary mill with 1 wt % Si and uncontrolled impurities (O and C). An assumption was put forward about the mechanisms of HCM hardening: when using homogenized Nb (without silicon), the hardening proceeds by two mechanisms, both by the cold-work hardening of niobium powder (dislocation mechanism) and by the uncontrolled impurities (O and C) that form ultrafine oxides and niobium carbides (dispersion hardening); after Si introduction, an additional dispersion hardening with niobium silicides takes place. The authors do not exclude the effect of porosity on the strength of the material.