Fabrication and characterization of pure tungsten using the hot-shock consolidation

Crack-free pure W bulks have been fabricated by SHS assisted hot-shock consolidation (HSC). The tungsten powders were preheated by the heat released through a SHS (self-propagating high-temperature synthesis) reaction before shock wave loading. The duration of preheating was less than 3 min and the preheating temperature was controlled in the range of 700 ∼ 1300 C by adjusting the mass of the SHS mixture. The highest relative density of compacted samples can reach 96.7% T.D. (theoretical density) at 1300 C under the shock pressure of 3.14GPa. The grain sizes of all compacted samples are nearly the same as the initial powder size of 2 μm. The hardness and modulus of the consolidated pure W bulks were measured using nanoindentation test; and the microstructure was investigated using light microscopy (LM) and scanning electron microscopy (SEM). It is found that the shock pressure plays a more important role than preheating temperature, after the pressure exceeding the crush strength of tungsten powder during the sintering process. At the preheating temperature of 1300 C, the increase in shock pressure leads to obvious surface melting. For HSC of pure tungsten, the void collapse and surface melting are the main sintering mechanisms. The former one contributes to the densification behavior of powders, and the later one is responsible for the inter-particle bonding; and both of which are dominated by the shock pressure. The advantage of preheating for eliminating the cracks is also demonstrated by the experimental results.