Manipulation of microstructure and mechanical properties during dehydrogenation of hydrogen-sintered Ti–6Al–4V

Dunstan, Matthew K.; Paramore, James D.; Fang, Zhigang Zak; Sun, Pei

doi:10.1016/j.msea.2019.138244

Cited by 13 publications

(13 citation statements)

References 22 publications

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“…Such a microstructure has been previously documented by the authors to result from an excessive dehydrogenation temperature (i.e., 800-850°C). 31 Unintentional overheating during dehydrogenation in the specific furnace used in this study has been previously experienced by the authors, resulting from the thermocouple not being properly arranged in the hot zone. As such, the observed difference in microstructural evolution was due to equipment/experimental error, and not to the process itself.…”

Section: Resultsmentioning

confidence: 93%

“…Recently, it has been found that a similar gradient is produced when using higher dehydrogenation temperatures. 31 This is the result of a hydrogen concentration gradient that is produced during dehydrogenation, and due to the fact that hydrogen is a strong b stabilizer. If certain temperatures are reached before sufficient hydrogen is removed, the regions of higher hydrogen concentration near the center completely transform to b, which coarsens the microstructure.…”

Section: Discussionmentioning

confidence: 99%

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Powder Casting: Producing Bulk Metal Components from Powder Without Compaction

Paramore

Dunstan

Butler

et al. 2020

JOM

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Powder casting was developed to produce metal components with near-theoretical density from low-cost, loose powder using hydrogen sintering and phase transformation. This has significant implications for non-beam metal additive manufacturing processes (e.g., metal extrusion AM, binder jetting, and ordered powder lithography), which produce green parts with relatively low densities. Additionally, powder casting can enable the production of geometries typically not suitable for powder processing, such as plate and bar stock. In the current study, Ti-6Al-4V, Zr, and Hf were densified to 99.2%, 95.7%, and 94.0% of their respective theoretical densities, when sintered from loose powder at 1200°C for 4 h. The relative density and pore size distributions of Ti-6Al-4V produced by powder casting were very similar to those produced by press-and-sinter HSPT. The powder-cast Ti-6Al-4V samples also displayed ductility consistent with press-and-sinter HSPT. However, they exhibited lower strength due to unintentional overheating during the dehydrogenation step.

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Section: Resultsmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Powder Casting: Producing Bulk Metal Components from Powder Without Compaction

Paramore

Dunstan

Butler

et al. 2020

JOM

Self Cite

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“…THT usually consists of the process sequence solution treatment (ST), diffusion-controlled hydrogen uptake (hydrogenation), hydrogen degassing (dehydrogenation) and aging. With few exceptions [3] it is applied to Ti alloys only, aiming for homogeneous microstructure adaptation [4][5][6][7][8][9][10][11][12] and the generation of microstructural gradient [13,14]. A schematic visualization of the process, embedded into the Ti-6Al-4V/hydrogen phase diagram is shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen as a Temporary Alloying Element for Establishing Specific Microstructural Gradients in Ti-6Al-4V

Schmidt

Christ

Hehl

2022

Metals

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Parts of vehicles, such as landing gear components of aircrafts, are subject to growing demands in terms of sustainability via lightweight design and durability. To fulfill these requirements, the development of thermochemical processes is auspicious. Titanium alloys allow a heat treatment in hydrogen-containing atmosphere for temporary hydrogen alloying, often called thermohydrogen treatment (THT). The investigation presented intends to realize a local microstructure modification of Ti-6Al-4V by means of THT. The study aims to use hydrogen (H) as a promoter for changing the local distribution and morphology of strengthening precipitates during THT as well as the local grain size (microstructural gradient). Both shall improve the fatigue properties of the material after hydrogen degassing. To derive suitable thermohydrogen treatment process parameters, the resulting fatigue crack propagation resistance and fracture toughness after different solution heat treatments are determined experimentally and compared to each other. Moreover, various graded microstructures are evaluated after hydrogen uptake (hydrogenation) and hydrogen degassing (dehydrogenation) using numerically simulated hydrogen concentration profiles, observed hardness curves, metallographically determined microstructure gradients and the corresponding results of the phase analysis by means of X-ray diffraction. The study shows that hydrogenation at 500 °C and dehydrogenation at 750 °C enables the generation of a promising microstructural gradient.

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“…The presence of hydrogen in metals is an essential technical and scientific problem, since hydrogen, penetrating in structural materials, initiates the formation of various types of defects and significantly affects physical and mechanical properties of metals and alloys [1][2][3][4][5][6]. Hydrogen embrittlement leads to accelerated depletion of the constructional element resource, which is especially characteristic in cases of the development of damage accumulation processes localised near various defects in the metal structure.…”

Section: Introductionmentioning

confidence: 99%

Positron Spectroscopy of Hydrogen-Loaded Ti-6Al-4V Alloy with Different Defect Structure

et al. 2020

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The defect structure of annealed cast, electron beam melted and ultrafine-grained titanium Ti-6Al-4V alloys before and after hydrogenation was studied. It has been established that before hydrogenation the predominant types of defects in electron beam melted and ultrafine-grained titanium alloy are dislocations and low-angle boundaries, respectively. The cast alloy after annealing is defect-free material. Hydrogenation from the gas phase to 1.00 ± 0.15 wt% leads to an increase of the concentration of the predominant type of defects. Moreover, vacancy complexes also presented in electron beam melted and ultrafine-grained Ti-6Al-4V alloys interact with hydrogen and form hydrogen-vacancy complexes.

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Manipulation of microstructure and mechanical properties during dehydrogenation of hydrogen-sintered Ti–6Al–4V

Cited by 13 publications

References 22 publications

Powder Casting: Producing Bulk Metal Components from Powder Without Compaction

Powder Casting: Producing Bulk Metal Components from Powder Without Compaction

Hydrogen as a Temporary Alloying Element for Establishing Specific Microstructural Gradients in Ti-6Al-4V

Positron Spectroscopy of Hydrogen-Loaded Ti-6Al-4V Alloy with Different Defect Structure

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