| Technology of hydrogen treatment for titanium alloy is a kind of new system for completing optimum control of Ti-H microstructure and improving process ability by means of using hydrogen induced plasticity , hydrogen induced phase transformation and effect of reversible hydrogen alloying. Hydrogen treatment for titanium alloy can modify microstructure , mechanical properties and process capability , such as metal forming , diffusion process , machining and alternative process for casting titanium alloy.In this paper, the study fruits in relation to thermohydrogen treatment theory put forward by former researchers were introduced first, especially, the theoretical and practical developments in aspect of thermohydrogen treatment in completing optimum control of microstructure of titanium alloys and improving process ability by means of using hydrogen induced plasticity, hydrogen deduced phase transformation and effect of reversible hydrogen alloying. From the basis, the influences of thermohydrogen treatment on microstructure and hardness prbpertie for two different types of titanium alloys - α + β alloy TC21 and P alloy Ti40 were investigated, additionally, the mechanism of fining microstructure and improving process capability were analyzed.Samples with size of 10mm × 10mm × 3mm were adopted, including two alloys and each alloy in two stages: as-cast and as-forged. Hydrogen contents of the samples are 0.1wt%, 0.2et%, 0.3wt%, 0.4wt%, 0.5wt% and that without hydrogenation. Microstructure of specimens without hydrogenation, as-hydrogenated, and dehydrogenated were invastigated by OM, SEM, AND TEM respectively.Researches reveal that hydrogen induces strain by increasing their lattice parameters, expending their cell volumes and enhancing the dislocations motion. With the hydrogen concentration increasing hydronides TixHy could be formed.Test results show that Thermohydrogen treatment can refining the microstructure of titanium alloys TC21 but it has less effect on P titanium alloys Ti40.
|
PDF Full Text Request