The trapping effect of transitional metals on oxygen in Mo from first-principles calculations

Abstract

The trapping effect of solute on oxygen (O) can be benefit for inhibiting its segregation and embrittlement at the GBs in Mo alloys. In this work, the interaction between solutes (including 27 transition metals), interstitial O and vacancy in Mo are implemented by first-principles calculations, and their trapping effects on O are evaluated by Simonovic’s model. Single transition metal solute (TMS) has a strong attraction for O, and it is strengthened by the second solute for all 3d, oversized 4d and 5d series. Furthermore, there is a significant synergistic effect between solute, vacancy, and oxygen for oversized solutes, i.e., the binding energy between solute atom (vacancy) and oxygen atoms is enhanced by the presence of vacancy (solute). The distribution of oxygen indicates that oxygen can be captured by dilute TMS atoms, and more oxygen atoms will be trapped as the solute concentration increases in Mo. Based on our extensive calculations, Sc, Ti, Zr, Hf, and Ta can be the top priority for suppressing the segregation and embrittlement of O in Mo alloys. It is interesting that the interaction between solute and O can be accurately separated into elastic and chemical contributions though delicate calculation, and the counterintuitive strong binding effect of fifth-nearest solute-O pairs for undersized 4d and 5d elements is owning to the chemical contribution driven by Coulomb interaction.