Exploring the Formation Mechanism, Evolution Law, and Precise Composition Control of Interstitial Oxygen in Body-Centered Cubic Mo

Interstitial oxygen (O) on the formation mechanism and enrichment distribution of body-centered cubic (BCC) molybdenum (Mo) has rarely been reported, and the O usually can cause serious brittle fracture in Mo. In this paper, we studied the formation mechanism and evolution of oxygen (O) when it was precisely controlled in the range of 3700-8600 parts per million (wppm). It was found that, with an increase in O concentration, O element not only existed in the form of solid solution but generated O element with different valence states in Mo metal. Large amounts of MoO2, MoO3, and Mo4O11 intermediate oxides were identified by electron probe micro-analyzer (EPMA) and X-ray photoelectron spectroscopy (XPS). Thermodynamic calculations revealed the formation process of oxides, and authenticity of the presence of O was verified by XPS. Enrichment and distribution of O element were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and EPMA. Moreover, the compressive yield strength and hardness of Mo were greatly affected by O content range of 4500-8600 wppm. Our study is helpful to understand the behavior of interstitial impurity O in refractory Mo metals and provides important guidance for development of high-purity rare Mo metals.

Automated summary

This paper investigates the formation mechanism and enrichment distribution of interstitial oxygen in body-centered cubic (BCC) molybdenum. It is found that oxygen exists in the form of solid solution and generates different valence states in Mo metal with increasing concentration. The presence of MoO2, MoO3, and Mo4O11 intermediate oxides is confirmed, and the formation process of oxides is revealed. The enrichment and distribution of oxygen are analyzed, and it is shown that the oxygen content significantly affects the compressive yield strength and hardness of Mo. This study provides important insights into the behavior of interstitial oxygen in refractory Mo metals and guides the development of high-purity rare Mo metals.