Interaction of Praseodymium and Dysprosium with Oxygen in Nickel Melts at PAr = 0.1 MPa and Analysis of Nonmetallic Inclusions.

Interaction of Pr/Dy with oxygen in nickel melts at P_Ar = 0.1 MPa and constant temperature was studied using the EMF instantaneous fixing method using a Mo[Cr/Cr₂O₃//ZrO₂(MgO)//O(Ni_l)]Mo cell and certified sensors. Dependences a_[O] = f[Pr/Dy, %] expressed in the form of logarithmic equations made it possible to compare them with each other in the concentration range of 0.001–0.2 wt % of each deoxidizer and determine that the deoxidizing ability of Pr is 1.7 times higher compared to Dy. The activity of oxygen a_[O] in Ni–O–Al–(Pr/Dy) melts was calculated in comparison with Al at a concentration of 0.05 wt % of elements and its sevenfold decrease was shown for the first deoxidizer and elevenfold for the second. The morphology of nonmetallic inclusions in metallographic sections of Ni–O–Pr/Dy alloys has been studied, indicating that the inclusions are located along grain boundaries and have different configurations and a complex heterophase composition. Analysis of nonmetallic inclusions with the maximum content of deoxidizing element proved the existence of Pr/Dy oxygen compounds, which confirmed the data of thermodynamic and mass spectrometric studies. The average content of Zr in nonmetallic inclusions during the deoxidation of Pr is two times higher than in experiments during the deoxidation of Dy, which indicates the interaction of Pr/Dy with the EMF ZrO₂ sensor and the preferential interaction of Pr compared to Dy and correlates with the data on the determination of a_[O]. [ABSTRACT FROM AUTHOR]