Abstract
Spark plasma sintering (SPS) is widely used for the consolidation of different materials. Copper-based pseudo alloys have found a variety of applications including as electrodes in vacuum interrupters of high-voltage electric circuits. How does the kinetics of SPS consolidation for such alloys depend on the heating rate? Do SPS kinetics depend on the microstructure of the media to be sintered? These questions were addressed by the investigation of SPS kinetics in the heating rate range of 0.1 to 50 K/s. The latter conditions were achieved through flash spark plasma sintering (FSPS). We also compared the sintering kinetics for the conventional copper–chromium mixture and for the mechanically induced copper/chromium nanostructured particles. It was shown that, under FSPS conditions, the observed maximum consolidation rates were 20–30 times higher than that for conventional SPS with a heating rate of 100 K/min. Under the investigated conditions, the sintering rate for mechanically induced composite Cu/Cr particles was 2–4 times higher compared to the conventional Cu + Cr mixtures. The apparent sintering activation energy for the Cu/Cr powder was twice less than that for Cu–Cr mixture. It was concluded that the FSPS of nanostructured powders is an efficient approach for the fabrication of pseudo-alloys.
Highlights
Copper-based composites, which involve immiscible elements (e.g., Cr, W, Mo), so-called pseudo-alloys, have attracted a vast of attention for a variety of applications including a new generation of electrical contacts, electrodes for point welding, and radiators, etc. [1,2,3,4,5,6]
We report the results on the consolidation kinetics of the Cu–Cr pseudo alloys, in a wide range of heating rates including the so-called, flash spark plasma sintering (SPS) mode [30], with heating rates up to 50 K/s
The sintering rates for the mechanically induced composite Cu/Cr particles were 2–4 times higher compared to that for the conventional Cu + Cr mixtures during both the isothermal and nonisothermal stages; (ii) The apparent sintering activation energy for the Cu/Cr powder was approximately twice lower than that for the Cu + Cr mixture; (iii) The sintering rate was much faster in the preheating stage compared to the isothermal stage for both mixtures; and (iv) The higher heating rate resulted in a higher consolidation rate
Summary
Copper-based composites, which involve immiscible elements (e.g., Cr, W, Mo), so-called pseudo-alloys, have attracted a vast of attention for a variety of applications including a new generation of electrical contacts, electrodes for point welding, and radiators, etc. [1,2,3,4,5,6]. The SPS method allows for a precise variation of the sintering parameters, including the preheating rates. There are a vast number of publications, both theoretical [23,24,25,26] and experimental [27,28,29], on the SPS of different ceramics and alloys, while much less works have reported the consolidation of the pseudo-alloys. We report the results on the consolidation kinetics of the Cu–Cr pseudo alloys, in a wide range of heating rates including the so-called, flash SPS mode [30], with heating rates up to 50 K/s. We compared the SPS kinetics for the conventional Cu + Cr mixture and composite Cu/Cr nanostructured particles fabricated by the HEBM method
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