Use of Self-Propagating High-Temperature Synthesis Reactions in Refractory Alloy Fabrication

摘要

The titanium carbide (TiC) self-propagating high-temperature synthesis (SHS) reaction was used in a hot-explosive-consolidation process to fabricate tungsten and molybdenum-based alloy billets. In this method, a Ti+C mixture is reacted to provide a source of heat for the refractory precursor powders. As the TiC reaction proceeds, the exterior of the alloy sample heats up rapidly, near or above 2000 deg C, while its interior lags behind, heating up more gradually to 1600 deg C. At the completion of the TiC reaction, the alloy sample s exterior begins to cool, causing the temperature to equilibrate to an isothermal condition. At this time, the sample is compacted to high density by the application of an explosively generated pressure wave. Experiments were conducted to determine the relationship between the geometries of the Ti+C mixture and the alloy sample. For the Ti+C mixture, a doughnut arrangement was found to provide an optimum heating rate and temperature profile to the sample. The effects of the relative amount of the SHS material and alloy sample on the duration of the heating cycle, peak interior temperature, and rate of cooling were studied. The properties of the samples and TiC product were evaluated by density measurements, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction analysis. The HEC method and the resultant product structures are described.