Abstract
The difficulty of achieving full densification of TiAl powder by pressureless sintering makes spark plasma sintering (SPS) an attractive alternative. In this study, Ti-48Al-2Cr-Nb alloy was fabricated by SPS from gas-atomized TiAl powder. Near-full densification was achieved after 4 min at 1100°C under applied pressure of 80 MPa, accompanied by the formation of an unexpected bright-contrast phase when observed under backscattered scanning electron microscopy. Detailed characterization revealed that the bright-contrast phase was composed of oxygen- and carbon-enriched α-Ti and chromium-enriched β-Ti. A two-particle model was used to simulate the current passing through the particles during SPS. The model predicts that when a high density of current passes through the narrow particle–particle contact area, it can produce a high-temperature zone (~ 1-μm-thick surface layer), in which the temperature is high enough to allow the decomposition of the surface oxide layer and melting of the TiAl alloy underneath. These complex changes lead to the formation of the unexpected phase.
Published Version
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