Effects of oxygen on microstructure and evolution mechanism of body-centred-cubic molybdenum

Molybdenum metal have high brittleness and ductile-to-brittle transition temperature (DBTT) due to the existence of interstitial oxygen impurities, so it is of great scientific significance to strictly control and accurately analyze the oxygen content. In this work, the effects of oxygen on microstructure and evolution mechanism of body-centred-cubic metallic molybdenum are studied. The X-Ray diffraction (XRD), oxygen nitrogen analyzer, scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and electron probe micro-analyzer (EPMA) are used to analyze the chemical composition, microstructure, oxygen existence and distribution form. The results demonstrate that Mo O specimens with up to 3300 ppm of oxygen content have single-phase body-centered cubic microstructure with no precipitates. When the oxygen content in molybdenum increases from 44 ppm to 2200– 3300 ppm, more oxygen exists in the pores between molybdenum grains, and the fracture mode changes from intergranular fracture to intergranular and transgranular mixed fracture. The microhardness increases with increase of oxygen content. These results provide new ideas for controlling the change trend of oxygen in molybdenum and regulating the properties of molybdenum.