| 1. |
- Ashrafi, Hamid, et al.
(författare)
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Void formation and plastic deformation mechanism of a cold-rolled dual-phase steel during tension
- 2020
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Ingår i: Acta Metallurgica Sinica (English Letters). - : Springer. - 1006-7191 .- 2194-1289. ; 33, s. 299-306
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Tidskriftsartikel (refereegranskat)abstract
- The void formation and plastic deformation micromechanisms of a cold-rolled DP600 steel during tensile loading were studied by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The SEM observations revealed that the main void nucleation mechanism in the DP600 steel is decohesion at the ferrite–martensite interfaces. The voids were mostly observed between the closely spaced martensite islands situated at the boundaries of relatively finer ferrite grains. The EBSD results indicated a strain gradient developed from the ferrite–martensite and ferrite–ferrite interfaces into the interior of ferrite grains during the tensile deformation, which led to a stress concentration at these interfaces. Moreover, it was demonstrated that local misorientation inside the finer ferrite grains surrounded by martensite islands was higher than that for the coarser ferrite grains, which made the former more prone to void initiation.
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| 2. |
- Liu, Hui, et al.
(författare)
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Helium Bubble Growth in He + Ions Implanted 304L Stainless Steel Processed by Laser Powder Bed Fusion During Post-Irradiation Annealing at 600 °C
- 2022
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Ingår i: Acta Metallurgica Sinica (English Letters). - : Springer Science and Business Media LLC. - 1006-7191 .- 2194-1289. ; 35:9, s. 1509-1518
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Tidskriftsartikel (refereegranskat)abstract
- The abundancy of defect sinks in the microstructure of laser powder bed fusion (LPBF) processed austenitic stainless steels was found to be beneficial for helium resistance. In the current study, the influence of the novel microstructure in LPBF processed 304L on the helium bubble growth behaviour was investigated using transmission electron microscopy in samples implanted with He+ ion and post-irradiation annealing treated at 600 °C for 1 h. Two variants of LPBF processed 304L samples were used, one in as-built condition and the other solution-annealed. The comparison between the two samples indicated that the helium bubble growth was inhibited and remained stable in the as-built sample but coarsened significantly in the solution-annealed sample. The sub-grain boundaries and oxide nano-inclusions acted as defect sinks to trap helium atoms and inhibited the growth of helium bubble in the as-built sample under the post-irradiation annealing conditions used.
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| 3. |
- Qiu, Siyi, et al.
(författare)
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A Brief Review on He Ion Irradiation Research of Steel and Iron-Based Alloys in Nuclear Power Plants
- 2023
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Ingår i: Acta Metallurgica Sinica (English Letters). - : Springer Science and Business Media LLC. - 1006-7191 .- 2194-1289. ; 36:4, s. 529-551
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Forskningsöversikt (refereegranskat)abstract
- Nuclear power plays a key role as renewable energy in alleviating the worldwide energy shortage. The material degradation caused by high-temperature and high-flux neutron irradiation is the most concerning issue for nuclear reactor safety. A large number of He atoms produced through the (n, alpha) transmutation reaction diffuse and migrate in metals and accumulate to form He bubbles because of the extremely low solubility of He atoms in metal materials. The helium bubbles gather at the grain boundary or grain to cause swelling, hardening, embrittlement, and other damages to the in-core structural components. This paper mainly summarizes the research progress on He irradiation in steel and iron-based alloys, including the diffusion and accumulation of He atoms, the nucleation and growth of He bubbles, and the microstructure and macroscopic degradation of material performance caused by He irradiation. The mechanism of helium irradiation-induced corrosion in steel and iron-based alloys in recent years is reviewed as well. Moreover, the investigations on irradiation performance in additive manufactured stainless steels are summarized, and the mechanism of irradiation resistance is prospected.
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| 4. |
- Xing, Lei-Lei, et al.
(författare)
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Microstructure of a Ti-50 wt% Ta alloy produced via laser powder bed fusion
- 2020
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Ingår i: Acta Metallurgica Sinica (English Letters). - : Springer Science and Business Media LLC. - 1006-7191 .- 2194-1289. ; 33, s. 981-990
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Tidskriftsartikel (refereegranskat)abstract
- Ti-Ta alloys have been widely studied for biomedical applications due to their high biocompatibility and corrosion resistance. In this work, nearly fully dense and in situ alloyed Ti-50 wt% Ta samples were fabricated by the laser powder bed fusion (LPBF) of mechanically mixed powders. With increased exposure time, and thereby increased laser energy density, insoluble Ta particles were almost dissolved, and a Ti-50 wt% Ta alloy was formed. Cellular and dendritic structures were formed due to constitutional undercooling, which was caused by the high cooling rate of LPBF process. Both retained beta phases and alpha '' phases were observed in the LPBFed Ti-50 wt% Ta alloy. The alpha '' phase was found at the boundary of the cellular structures, where the tantalum content was not high enough to suppress the bcc lattice transition completely but could suppress the beta phase -> alpha ' phase transition.
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| 5. |
- Yu, Chenfan, et al.
(författare)
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Effect of Build Direction on Fatigue Performance of L-PBF 316L Stainless Steel
- 2020
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Ingår i: Acta Metallurgica Sinica (English Letters). - : Springer Science and Business Media LLC. - 1006-7191 .- 2194-1289. ; 33:4, s. 539-550
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure and fatigue and tensile properties of 316L stainless steel fabricated via laser powder bed fusion (L-PBF) were investigated. Two 316L stainless steel specimens with different loading directions which are either perpendicular to or parallel to building direction were prepared by L-PBF process. The results of X-ray diffraction tomography showed that there was no significant difference in morphology and size/distribution of the defects in the HB and VB samples. Since long axis of columnar grains is generally parallel to the build direction, the fatigue crack encounters more grain boundaries in VB samples under cyclic loading, which led to enhanced fatigue resistance of VB samples compared with HB sample. In contrast to HB sample, the VB sample has a higher fatigue strength due to a higher resistance to localized plastic deformation under cyclic loading. The differences in fatigue properties of L-PBF 316L SS with different build directions were predominantly controlled by solidification microstructures.
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