| Abstract Scope |
Magnesiothermic reduction of Ta<sub>2</sub>O<sub>5</sub> is an important route for porous tantalum powder, but the correlation between Mg dosage, phase evolution, oxygen removal, and powder structure remains unclear. Using the Ta<sub>2</sub>O<sub>5</sub>–Mg reduction system as a model, different reduction conditions were constructed at 900 °C under Ar by regulating the Mg/Ta<sub>2</sub>O<sub>5</sub> molar ratio from 5 to 15, enabling evaluation of Mg availability on phase transformation, oxygen removal, and porous-particle evolution. Thermodynamic calculations, non-isothermal kinetic analysis, XRD, SEM, particle-size distribution, and oxygen-content measurements were used to establish the process–structure relationship. Results show that the reduction is thermodynamically favorable and follows an R3 contracting-sphere phase-boundary model. Increasing Mg addition suppresses stable magnesium tantalate by-products, promotes metallic Ta formation, decreases oxygen from 2.3846 to 0.5765 wt.%, and improves porous secondary-particle uniformity. This study provides guidance for regulating Ta<sub>2</sub>O<sub>5</sub> magnesiothermic reduction parameters and preparing structurally controlled tantalum powders. |