Densification, grain growth mechanism and mechanical properties of Mo[sbnd]10Nb refractory targets fabricated by SPS

Abstract

Refractory Mo10Nb targets were fabricated by spark plasma sintering (SPS) technology at an extensive range of preparation temperatures (900–1800 °C) and holding times (6–15 min) under 30 MPa. The densification and grain growth mechanisms of Mo10Nb targets sintered by SPS were revealed by the power-creep and grain growth models. Different effective stress (n) and grain growth exponents (m) corresponded to various densification and grain growth mechanisms. The densification mainly dominated at temperatures of 900 to 1300 °C, whereas the grain growth predominantly occurred at temperatures of 1400 to 1800 °C. The densification was basically controlled by particle rearrangement when n < 1. Besides, grain boundary diffusion was the major densification mechanism for n = 1–2, and the densification mechanism was the dislocation climbing when n was close to 3. The activation energies for densification were calculated to be 119.30 kJ/mol (n = 1) and 271.79 kJ/mol (n = 2). In addition, the grain boundary diffusion was regarded as the primary grain growth mechanism. The activation energies for grain growth were calculated to be 188.14 kJ/mol (t = 6 min), 172.49 kJ/mol (t = 10 min) and 137.85 kJ/mol (t = 15 min). Besides, compared with the grain size, the porosity was identified to be the cardinal influencing factor on the Vickers hardness of Mo10Nb targets sintered by SPS.