Synthesis in Hydride Cycle of Near-α Ti–8Al–1Mo–1V Alloy

This work presents a new method for synthesizing the widely used near-α Ti–8Al–1Mo–1V alloy. To this end, we sequentially used two methods: metal hydrides were synthesized by Self-propagating High-temperature Synthesis (SHS) method, and the said alloy was synthesized by Hydride cycle (HC) method, using the SHS-produced hydrides. The main point of the SHS method is to use of heat of the exothermic reaction, locally initiated in a thin layer of metal powder. The gist of the HC method, developed by us, is to use transition metal hydrides as starting materials for alloy synthesis. The approaches, elaborated in the present work, resulted in the synthesis of Ti–8Al–1Mo–1V alloy, consisting of 94 to 95.7 wt pct α-phase and 6 to 4.3 wt pct β-phase. The formation of the alloy proceeded according to the solid-phase mechanism. The alloy without crushing interacted with hydrogen in the SHS mode, forming a reversible hydride (Ti–8Al–1Mo–1V)H_1.28. Hydrogen enhanced the fragility of the hydride and made it possible to grind it to powder with particle sizes under 3 microns (even down to 100 nm and less) within 30 to 40 minutes, without contamination of the particle surfaces. Simultaneously, the presence of hydrogen in the crystal lattice of alloy hydride increased its plasticity. Compacting the hydride to the designed shape and the following by sintering dehydrogenation at temperature close to the hydride decomposition temperature, allowed us to get a product of a required form. The elaborated HC method for synthesizing of the near-α-alloy has significant advantages over the traditional methods: low temperature (1000 °C instead of 1800 °C to 2600 °C), short duration (0.5 to 1 hour instead of dozens of hours), one stage, ecologically friendly, energy-saving process, solid-phase mechanism without melting, etc. The elaborated HC methods for the synthesis of near-α Ti–8Al–1Mo–1V alloy and the synthesis of its hydride (Ti–8Al–1Mo–1V)H_1.28 by the SHS method can be of commercial and industrial interest.