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- Duan, Shengchao, et al.
(författare)
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Manufacturing an ultra-low-sulfur CoCrFeMnNi high-entropy alloy by slagging through induction melting with ferroalloys feedstock
- 2022
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 928, s. 167080-
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Tidskriftsartikel (refereegranskat)abstract
- Commercial ferroalloys are used in the manufacturing of a CoCrFeMnNi high-entropy alloy (HEA) due to their price advantage and the productivity of the manufacturing process. However, elemental impurities such as sulfur in ferroalloys can undermine the mechanical properties of HEAs. Therefore, the desulfurization behavior of a CoCrFeMnNi HEA using the CaO-MgO-Al2O3 (CAM) slagging method with alumina or magnesia refractories and ferroalloys raw material feedstock was investigated in an induction melting furnace at 1773 K to determine how to control the cleanness of the HEA. The resulting desulfurization ratios of the alloy were approx. 47% when refined by the CaAl2O4-MgAl2O4(CA-MA)-saturated slag in an Al2O3 refractory, whereas 94% when refined by the CaO-MgO(C-M)-saturated slag in a MgO refractory. The overall mass transfer coefficients of sulfur for the HEA refined by the CA-MA- and C-M-saturated slags at 1773 K were ko = 1.4 x 10 6 m/s and ko = 2.0 x 10 6 m/s, respectively, which are lower than the coefficients of iron- and nickel-based alloys at the same experimental conditions. The MnS inclusion particles can precipitate in the mushy zone rather than the liquid region when the solid fraction is close to 1.0, i.e., at the final stage of the solidification. The theoretical radius of MnS increases from 0 to 1.6 mu m when the sulfur content rises from 3 ppm to 60 ppm, according to the hypothesis that the mass transfer of sulfur in the HEA is the rate-controlling step.
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| 2. |
- Duan, Shengchao, et al.
(författare)
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Novel applications of ferroalloys for manufacturing of ultra-clean CoCrFeMnNi high-entropy alloy by slagging method
- 2023
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 939
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Tidskriftsartikel (refereegranskat)abstract
- The present study provides a benchmark of a sustainable solution utilizing ferroalloys to prepare ultra-clean CoCrFeMnNi high-entropy alloy (HEA). The designed CaO-MgO-Al2O3 slags saturated with CaAl2O4-MgAl2O4 (CA-MA, Slag A) and CaO-MgO (C-M, Slag M) were used to refine the HEA in Al2O3 and MgO refractory in an induction furnace under high-purity Ar atmosphere at 1773 K. The characteristics of non-metallic inclusions in the sampled HEA at different time intervals were quantitatively investigated. The results showed that three types of inclusions, i.e., sulfide (MnS), oxide, and complex type (oxide+sulfide), were found in the HEA regardless of refractory and slag types. The oxide inclusions such as MnAl2O4 and MgAl2O4 spinel particles can exist stably in the HEA melted in Al2O3 and MgO refractories with slag A and slag M, respectively. This fact is also confirmed not only by the electrolytic extraction method with elimination of the alloy matrix affection but also by the thermodynamic stability diagram for the HEA. For the structure of the complex inclusions, the core of oxide inclusions usually can act as the subsequent nucleation site for MnS since the precipitation temperature of the oxide inclusions (above the liquidus temperature of the HEA, TL approximately equal to 1623 K) is higher than that of MnS (below the solidus temperature of the HEA, TS approximately equal to 1573 K). The HEA melted in the MgO refractory with slag M had a higher cleanliness compared with that melted in the Al2O3 refractory with slag A, indicating that the MgO refractory with C-M saturated CaO-MgO-Al2O3 slag is suitable for producing an ultra-clean CoCrFeMnNi HEA prepared by the ferroalloys feedstock as the raw materials.
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