| Description |
The relationship between the grain size and mechanical properties of tungsten alloys was studied for potential improvement in ductility through minimization of grain size and for possible modification to the ductile-to-brittle transition temperature (DBTT) in powder metallurgy-produced alloys. In this study, nanoscale W powders were used to produce near full-density tungsten and several tungsten alloys. Pure W, and alloys of W with 0.5 wt.% and 1 wt.% of titanium hydride (TiH2), were prepared at several reduction temperatures (650 °C, 750 °C, and 850 °C) and were also prepared at several sintering temperatures (1200 °C, 1300 °C, and 1400 °C). Three-point bend (3-PB) tests were used to measure strength and ductility at elevated temperatures and to determine the DBTT of these tungsten alloys. Commercially purchased hot-rolled W was also tested to give some gauge of industrial materials currently in use. Different surface conditions of commercially purchased hot-rolled W samples were tested to determine the relationship between the DBTT and sample's surface finish of hot-rolled tungsten. Correlations were examined between ductility, DBTT, and the interrelated aspects of composition and grain size. Samples containing titanium (Ti) exhibited grain sizes of less than half those of pure W samples at all sintering temperatures tested, presumably due to grain boundary pinning by Ti-rich phases in the microstructure that deterred grain growth. |
