Abstract
A new strategy called melt hydrogenation was introduced in this study to improve the hot deformability of Ti2AlN/Ti46Al4Nb1Mo composites, which was directly melting materials in mixed gas of H2 and Ar with different ratios (H2 percentage: 0, 20% and 40%). XRD results showed that melt hydrogenation decreased the proportion of α2 phase, which was due to the narrowed α phase region and enlarged β phase region since hydrogen acting as β stable element. The length of Ti2AlN particles in as-cast composites increased, because hydrogen induced overheat on melt surface and then promoted the growth rate of Ti2AlN particles along their long axis. Hot compression results indicated melt hydrogenation effectively reduced the peak stress from 695 MPa to 605/603 MPa at 1100 °C/0.1 s−1 when H2 percentage was 20% and 40%, respectively. Deformed microstructure indicated that hydrogen accelerated dynamic recrystallization (from 55.6% to 74.7%) and increased the fraction of area with low density of dislocations (from 82.3% to 87.8%). In addition, hydrogen facilitated the formation of deformed nano-twins, which was probably due to hydrogen reducing the stacking fault energy. Therefore, the increased DRX, decreased dislocations density and more deformed nano-twins all contributed to the enhanced hot deformability of Ti2AlN/Ti46Al4Nb1Mo composites.
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