Research on aluminum component change and phase transformation of TiAl-based alloy in electron beam selective melting process under multiple scan

Zhou, Jun; Li, Hongxin; Yu, Yefeng; Li, Yang; Qian, Ya; Firouzian, Kevin; Feng, Lin

doi:10.1016/j.intermet.2019.106575

Cited by 41 publications

(11 citation statements)

References 24 publications

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“…10 (a) at around 4000 K, the temperature of nearly entire keyhole surface is above the boiling temperature and the temperature increases continuously from the upper to the bottom region of the keyhole. This temperature distribution indicates stronger evaporation from keyhole surface under the low ambient pressure, which follows the trend in previous experiments [40,43]. Moreover, the recoil pressure on the keyhole surface is distributed all over the keyhole surface with the value above 0.1 atm and up to 5 atm at the bottom of the keyhole.…”

Section: Reduce Keyhole Pores: Low Ambient Pressuresupporting

confidence: 86%

Mechanism of keyhole pore formation in metal additive manufacturing

Wang¹,

Zhang²,

Chia³

et al. 2021

Preprint

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Metal additive manufacturing has gained extensive attention from research institutes and companies to fabricate intricate parts and functionally graded materials. However, the porosity of the as-built part deteriorates the mechanical property and even hinders the further application of metal additive manufacturing. Particularly, the mechanisms of keyhole pores associated with the keyhole fluctuation are not fully understood. To reveal the mechanisms of the keyhole pores formation, we adopt a multiphysics thermalfluid flow model incorporating heat transfer, liquid flow, metal evaporation, Marangoni effect, and Darcy's law to simulate the keyhole pore formation process, and the results are validated with the in-situ X-ray images. The simulation results present the instant bubble formation due to the keyhole instability and motion of the instant bubble when it pins on the solidification front. Moreover, the unevenly distributed recoil pressure on the keyhole surface is an important factor for keyhole collapse and pentration. Furthermore, comparing the keyhole pore formation under different laser scanning speeds shows that the keyhole pore is sensitive to the manufacturing parameters. The keyhole fluctuation features and energy absorptivity variation on the rear keyhole wall could be metrics to evaluate the likelihood of the keyhole pore formation. Additionally, the simulation under a low ambient pressure shows the feaibility of improving the keyhole stability to reduce and even avoid the formation of keyhole pores.

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Section: Reduce Keyhole Pores: Low Ambient Pressuresupporting

confidence: 86%

Mechanism of keyhole pore formation in metal additive manufacturing

Wang¹,

Zhang²,

Chia³

et al. 2021

Preprint

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“…First studies were performed by Cormier et al [22]. In addition, further investigations regarding alloy design and process parameters were performed on Ti-45Al-7Nb-0.3 W [23], Ti-47Al-2Cr-2Nb [24][25][26] and Ti-48Al-2Cr-2Nb [27][28][29] alloys. Aluminum evaporation during the PBF-EB/M process was frequently observed and resulted in an irregular microstructure distribution [26,30,31].…”

Section: Introductionmentioning

confidence: 99%

Characterization of the high-temperature behavior of PBF-EB/M manufactured γ titanium aluminides

et al. 2022

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Due to their high specific strength and temperature resistance, γ-titanium aluminides (γ-TiAl) have a growing importance for automotive and aerospace applications. However, conventional processing is very challenging due to the inherent brittleness of the material. Therefore, new manufacturing techniques and methods have to be established. Additive manufacturing techniques such as electron powder bed fusion (PBF-EB/M) are favored, since they enable near net shape manufacturing of highly complex geometries. The high preheating temperatures, which typically occur during PBF-EB/M, can significantly improve the processability of TiAl and facilitate the fabrication of complex parts. In this study, a previously optimized material condition of the β-solidifying TNM alloy TNM-B1 (Ti-43.5Al-4Nb-1Mo-0.1B) was manufactured by PBF-EB/M. The resulting microstructure, defect distribution and morphology, and mechanical properties were characterized by means of characterization methods, e.g., CT, SEM, light microscopy, hardness measurements, and tensile tests. A special focus was on the mechanical high-temperature behavior. The pronounced sensitivity of the material to defects and internal notches, e.g., due to lack of fusion defects (misconnections) which were found in the as-built condition, was identified as a main cause for premature failure below the yield point due to the low ductility. This failure was analyzed and potential improvements were identified.

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“…The recycling of the sintered powder greatly increases the material utilization rate. In recent years, metal parts with high mechanical properties have been successfully fabricated by EB-PBF using different materials [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ], which demonstrates promising prospects in aerospace, medicine and other fields.…”

Section: Introductionmentioning

confidence: 99%

Performance of High-Layer-Thickness Ti6Al4V Fabricated by Electron Beam Powder Bed Fusion under Different Accelerating Voltage Values

Liang

et al. 2022

Materials

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The electron beam powder bed fusion (EB-PBF) process is typically carried out using a layer thickness between 50 and 100 μm with the accelerating voltage of 60 kV for the electron beam. This configuration ensures forming accuracy but limits building efficiency. The augmentation of the accelerating voltage enlarges the molten pool due to the rise in penetrability, suggesting that a higher layer thickness can be used. Therefore, the effects of layer thickness and accelerating voltage were investigated simultaneously in this study to explore the feasibility of efficiency improvement. Ti6Al4V was fabricated by EB-PBF using layer thicknesses of 200 and 300 μm. Two accelerating voltage values of 60 and 90 kV were used to study their effects under expanded layer thickness. The results reveal that dense parts with the ultimate tensile strength higher than 950 MPa and elongation higher than 9.5% could be fabricated even if the layer thickness reached 300 μm, resulting in a building rate of up to 30 mm3/s. The expansion of the layer thickness could decrease the minimum bulk energy density needed to fabricate dense parts and increase the α platelet thickness, which improved the energy efficiency. However, expanding layer thickness had a significant negative effect on surface roughness, but it could be improved by applying augmented accelerating voltage.

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Research on aluminum component change and phase transformation of TiAl-based alloy in electron beam selective melting process under multiple scan

Cited by 41 publications

References 24 publications

Mechanism of keyhole pore formation in metal additive manufacturing

Mechanism of keyhole pore formation in metal additive manufacturing

Characterization of the high-temperature behavior of PBF-EB/M manufactured γ titanium aluminides

Performance of High-Layer-Thickness Ti6Al4V Fabricated by Electron Beam Powder Bed Fusion under Different Accelerating Voltage Values

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