The rapid densification behavior of powder metallurgy Ti alloys by induction heating sintering

Abstract

Micropores are decisive to mechanical properties and thermal deformation capabilities of powder metallurgy (P/M) Ti alloys sintered compacts. As a result, achieving express densification is of prime importance and has attracted increasing attention recently. Induction heating owns the merits of high efficiency, short process, and low cost, and thus has huge potential to be used as a sintering approach for the fabrication of P/M Ti alloys. Nevertheless, the facilitated densification behavior associated with induction heating sintering remains unclear so far. To address it, powder metallurgy Ti6Al4V is manufactured via induction heating sintering with which the underlying sintering mechanism is investigated in-depth. It is found that induction heating could generate a fully densified compact in a remarkably shortened time, demonstrating its superior sintering efficiency as compared with conventional resistance furnace heating. COMSOL finite element analysis reveals that the maximum current density during induction heating can reach 106 A m–2 though the magnetic field strength is solely 0.02 T, leading to a slight temperature difference of approximately 30 °C between the interior and exterior of the billet. Furthermore, the rapid heating essentially starts at sharp corners of particles due to the potent current concentration effect, which facilitates the cracking of the particle surface oxide film and thus enhances the direct contact between them. Moreover, the electromigration effect caused by induction current promotes the diffusion capability of elements, giving rise to expedited densification, alloying, and chemical homogenization. This work provides not only critical insight into the sintering mechanism of induction heating sintering but also significant guidance for low-cost powder metallurgy materials preparation.