Refinement of β Grain Size Due to TiB or Y_2O_3 Precipitates in Titanium Alloy

摘要

The refinement of β grain size by the use of TiB or Y_2O_3 precipitates in titanium alloy was studied in the temperature range from 1273 to 1673K. The column-shaped SP-700 alloys containing these compounds were prepared by blended elemental powder metallurgy using powders of HDH titanium, master alloy, TiB_2 and Y_2O_3. The volume fraction of these additives was widely varied from 0.025% to 2.0%. Alloys with no additives prepared by using HDH and Hunter titanium powders showed a tiny grain growth at heating temperatures up to 1573K, and the latter alloy resulted in the smaller β grain size. Enhanced β grain refinement was obtained by addition of TiB or Y_2O_3 and grain size was refined continuously with the increase of the volume fraction of these additives. The marked grain growth took place at the heating temperature of 1673 K. in alloys with the additive content of less than 0.10 %, indicating a reduction of porosity numbers, or dissolution or coarsening of precipitates.