Guide
An advanced melt hydrogenation method is introduced. TiB+TiC/Ti-6Al-4V composites were prepared by direct melting in a mixture of H2 and Ar. Melt hydrogenation improves the thermal processing performance of TMC in the (α + β) phase region, reducing the peak stress from 371 MPa to 271 MPa at 800 °C/1 s−1 and from 119 MPa to 60 MPa at 900 °C/0.01 s−1, expanding the optimal thermal processing window. The proportion of DRX grains increased from ~56% to ~81%, mainly due to the acceleration of migration at DRX grain boundaries and the decrease in dislocation density.
In-situ prepared titanium matrix composites (TMCs) have the advantages of low density, high specific strength, clean bonding interface, excellent corrosion resistance and oxidation resistance, and have broad application prospects in the aerospace field. Due to their high hardness, high modulus of elasticity and excellent thermal stability, TiB and TiC are ideal reinforcement materials for TMCs. However, the Ti-6Al-4V base alloy has poor hot workability, high deformation resistance, low forming limit, and narrow hot working window. The addition of ceramic particles such as TiB and TiC will produce large deformation stresses, which further increases the difficulty of forming TMCs during thermal processing.
Hydrogenation is a feasible method to improve the hot workability of titanium alloys. Traditional hydrogenation methods can reduce the deformation stress during thermal processing, but the efficiency is low. There is still a lack of systematic research on the effects of melt hydrogenation on the morphology and distribution of ceramics, the microstructure of the base alloy and the thermal processing window.
基于此，哈工大王亮教授研究团队引入了一种先进的熔体加氢方法，实现在熔体过程中进行加氢，制备(TiB+TiC)/ Ti-6Al-4V复合材料，系统研究氢对TMCs微观组织演变、高温变形行为和热加工窗口的影响。 研究结果以题为“Superior hot workability of (TiB+TiC)/Ti-6Al-4V composites fabricated by melt hydrogenation”发表于期刊《Journal of Alloys and Compounds》。
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It was found that the length of TiB whiskers increased. Due to the overheating of hydrogen on the melt surface, ceramic particles tend to aggregate at the primary β grain boundaries. The thermal processing diagram shows that the ideal processing window for unhydrogenated TMCs is 775 ~ 850 °C + 0.001 ~ 0.005 s−1, and the ideal processing window after melt hydrogenation is expanded to 825 ~ 950 °C + 0.001 ~ 0.01 s−1 and 900 ~ 950 °C + 0.5 ~ 1 s−1, indicating that TMCs can be processed at higher strain rates.
Hydrogen can accelerate the migration of DRX grain boundaries and favor DRX grain formation. The increase in the number of DRX grains consumes more dislocations, increasing the mobility of dislocations, resulting in a decrease in dislocation density, which is the main reason for the improvement in thermal processability.
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