Processing of fine-grained W materials without detrimental phases and their mechanical properties at 200–432 K

Low-temperature ductility improvements of tungsten (W) materials with microstructures of fine grains and fine transition metal–carbide dispersoids require sufficient reductions for consolidates that are free from detrimental dispersoids of the W2C phase. In this paper the cause of the occurrence of the detrimental W2C phase is studied and an appropriate processing method for its prevention and nearly full densification of mechanically alloyed powder is shown. By applying the method W–0.3 wt%Ti–0.006 wt%C (W–0.3TiC–0.006C) specimens with a negligible amount of the W2C phase and reductions up to 78% were prepared. It is found that W–0.3TiC–0.006C exhibits an appreciable ductility even at room temperature by three-point bend impact tests and static tensile tests, with the ductile-to-brittle transition temperature of around 260 K. The observed ductility is likely due to elongated, very thin grain structures of the material. For further ductility improvements, control of oxygen impurities to suppress decarburization during sintering and assure appropriate amounts of (Ti,W)C dispersoids is required.