Characteristics of AlN inclusions in low carbon Fe–Mn–Si–Al TWIP steel produced by AOD-ESR method

A characterization of non-metallic inclusions in Fe-Mn-Si-Al twinning-induced plasticity (TWIP) steels during argon oxygen decarburization-electroslag remelting-forging (AOD-ESR-forging) process has been performed. The two main kinds of inclusions found in TWIP-AOD ingots are single Al(O)N and MnS(Se)-Al(O)N aggregates. After the ESR process, Al(O)N and MnS(Se) inclusions in all size ranges significantly decrease while other kinds of inclusions show only minor changes. In the present study, the precipitation, growth, and dissolution of AlN and MnS inclusions have been analyzed by thermodynamics and kinetics. It is found that AlN inclusions in TWIP steels can already precipitate in the liquid. Furthermore, AlN inclusions precipitated in the liquid TWIP steels can act as the heterogeneous nuclei of MnS inclusions, and thus forming Al(O)N and MnS(Se) Á Al(O)N clusters. After ESR refining, the precipitation temperature of AlN and MnS inclusions will be significantly decreased, and AlN inclusions cannot be formed in the liquid TWIP steels in particular. The kinetic analysis show that the growth of AlN inclusions will be difficult during the ESR process, because their growth rate decreases significantly, while the dissolution rate increases.

Section: Thermodynamics Of Aln and Mns In Twip Steelsmentioning

confidence: 99%

Section: Thermodynamics Of Aln and Mns In Twip Steelsmentioning

confidence: 99%

Section: Experimental Materials and Inclusions Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

Characterization and Analysis of Non-Metallic Inclusions in Low-Carbon Fe-Mn-Si-Al TWIP Steels

Liu

Michelic

et al. 2016

“…During solidification, the driving force for the formation of AlN increases due to the enrichment of Al and N at the solidification front. The concentration of [%Al] and [%N] in the liquid phase at the solidifying front and solid fraction (

g_{normals}

) can be calculated using the Scheil equation . The equations for [%Al] and [%N] are given in Equation and .

[% Al] = {[% Al]}_{0} {(1 - g_{normals})}^{(k_{Al} - 1)}

[% N] = \frac{{false[% normalN false]}_{0}}{k_{normalN} + (1 - k_{normalN}) (1 - g_{normals})}

where [%Al] 0 and [%N] 0 are the initial weight percentages of solute Al and N in liquid steel, respectively.…”

Section: Discussionmentioning

confidence: 99%

Investigation of Inclusion Formation in Light‐Weight Fe–Mn–Al Steels using Automated Scanning Electron Microscope Equipped with Energy‐Dispersive X‐Ray Spectroscopy

Alba

Nabeel

Dogan

2019

Herein, the effect of Mn content on the characteristics and the formation of inclusions in light‐weight Fe–Mn–Al steels is investigated. Three laboratory‐produced steels, containing different manganese contents (2%, 5%, and 20%) are investigated. 2D and 3D inclusion characterization methods are used to establish inclusion classification rules for oxide, sulfide, and nitride inclusions using an automated scanning electron microscope (SEM) equipped with energy‐dispersive X‐ray spectroscopy (EDS) (ASPEX system). The observed inclusions are classified into Al2O3(pure), Al2O3–MnS, AlN(pure), AlN–MnS, AlON–MnS, AlON, and MnS. The results show that an increased Mn content of steel increases the number of inclusions, especially Al2O3–MnS and AlN–MnS inclusions. In the case of Al2O3–MnS inclusions, Al2O3 inclusions serve as the site for precipitation of MnS. Thermodynamic calculations suggest that the AlN‐containing inclusions formed during cooling and solidification of steels. Moreover, the formation of AlN–MnS inclusions can take place by the nucleation of MnS on AlN inclusions and vice versa.

Study on Micro Segregation of High Alloy Fe–Mn–C–Al Steel

Shen

Yang

Liu

et al. 2019

The segregation patterns of solute elements in the Fe–17.1Mn–0.24C–1.38Al steel are systemically investigated by experiments and simulations. The electron probe microanalyzer (EPMA) is conducted to assess possible micro segregation. The result indicates that with the increase of solid fraction in dendrite arms, Mn shows a positive segregation tendency, C uniformly distributes, and Al content slightly fluctuates. Compared with micro segregation models, experimental results of C match well with the Brody‐Fleming model. The segregation ratios of Mn are in good agreement with the lever‐rule. There is no certain regularity displayed between the experimental and calculation results about the segregation ratios of Al. The matrix of the steel is inhomogeneous with severe Mn and C micro segregation in the inter dendritic zone, whereas Al shows the opposite trend. A multicomponent phase field method coupled to thermodynamic calculations is used to simulate the concentration profiles of solute elements in the dendrite arms, and the numerical results are in favorable agreement with the experimental ones. Finally, the roles of undercooling and cooling rate on dendrite morphology and micro segregation of Mn are investigated. It reveals that large undercoolings could improve Mn segregation, while cooling rates have little effect on the maximum Mn segregation concentration but contribute to reduce the total inter dendritic Mn amount. They both have refinement effects on the dendritic structure. Those are helpful to understand and improve the segregations in Fe–Mn–C–Al steels.