Abstract
In this study, synchrotron radiation computed tomography was applied to investigate the mechanisms of titanium powder microwave sintering in situ. On the basis of reconstructed images, we observed that the sintering described in this study differs from conventional sintering in terms of particle smoothing, rounding, and short-term growth. Contacted particles were also isolated. The kinetic curves of sintering neck growth and particle surface area were obtained and compared with those of other microwave-sintered metals to examine the interaction mechanisms between mass and microwave fields. Results show that sintering neck growth accelerated from the intermediate period; however, this finding is inconsistent with that of aluminum powder microwave sintering described in previous work. The free surface areas of the particles were also quantitatively analyzed. In addition to the eddy current loss in metal particles, other heating mechanisms, including dielectric loss, interfacial polarization effect, and local plasma-activated sintering, contributed to sintering neck growth. Thermal and non-thermal effects possibly accelerated the sintering neck growth of titanium. This study provides a useful reference of further research on interaction mechanisms between mass and microwave fields during microwave sintering.
Highlights
As an advanced material preparation method, microwave sintering has been extensively investigated because of its numerous advantages, such as high heating rate, overall and even heating, and material microstructure improvement
Further analysis was conducted on the basis of 2D images to present microstructure evolution and to obtain parameters
The cross-sections of the same microstructure features at different sintering times were extracted on the basis of the reconstructed images
Summary
As an advanced material preparation method, microwave sintering has been extensively investigated because of its numerous advantages, such as high heating rate, overall and even heating, and material microstructure improvement. This technique is initially applied to nonmetallic material sintering. Since its first application performed by Roy et al in 1999, microwave sintering of metal, alloy, and metallic glassy powder has been investigated [1,2,3,4] This technique can promote particle size uniformity and densification rate; it can improve the macro-properties of materials to a greater extent than conventional sintering. Janney et al [2]
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