Phase Composition of Al-Si Coating from the Initial State to the Hot-Stamped Condition

Kučera, Vojtěch; Cabibbo, Marcello; Průša, Filip; Fojt, Jaroslav; Petr-Soini, Jaroslav; Pilvousek, Tomáš; Kolaříková, Marie; Vojtěch, Dalibor

doi:10.3390/ma14051125

Cited by 11 publications

(9 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4,45 Other compounds that have been identified as minority components after the hot-dipping process include τ 1 , τ 6 , η, and θ. 8,17,25,46 Previous studies have reported that θ and η form at ca. 650 °C, 14 τ 2 at 830 °C, 8 AlFe at 882 °C, 20 and τ 1 at 900 °C.…”

Section: ■ Discussionmentioning

confidence: 99%

“…The Al-Si coating undergoes a series of complex liquefaction-solidification reactions associated with the transfer of iron from the steel substrate to the coating. 5,17,18 Efforts to identify the chemical reaction steps associated with the overall reaction have largely focused on ex situ electron microscopic analysis of specimens heated within furnaces at different temperatures. 8,13,14,17,19−22 As-received samples typically consist of an Al-Si matrix atop a thin intermetallic layer at the steel-coating interface.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The Al-Si coating undergoes a series of complex liquefaction-solidification reactions associated with the transfer of iron from the steel substrate to the coating. ,, Efforts to identify the chemical reaction steps associated with the overall reaction have largely focused on ex situ electron microscopic analysis of specimens heated within furnaces at different temperatures. ,,,,− As-received samples typically consist of an Al-Si matrix atop a thin intermetallic layer at the steel-coating interface. The intermetallic interface forms during the dip-coating process, with τ 5 (Al 7 Fe 2 Si) and τ 6 (Al 4.5 FeSi) being the most commonly reported components. ,,,, Electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and electron back-scattering diffraction have been used to identify a range of intermetallic compounds that emerge during the coating transformation process, including the ternary Al-Fe-Si compounds commonly denoted τ 1 through τ 6 , and the binary phases η (Al 5 Fe 2 ), θ (Al 13 Fe 4 ), α 2 (AlFe), and ζ (Al 2 Fe). ,,,, The aluminum-rich corner of the ternary Al-Fe-Si phase diagram is complex, with numerous invariant reactions linking together three or more phases. ,, The gradual conversion of the Al-Si coating to a complete Al-Fe-Si intermetallic coating requires an increase in the Fe content of the coating, which means that the coating composition must change with time and temperature. This change in coating composition introduces the possibility of partial solidification and of localized interface-specific reactions.…”

Section: Introductionmentioning

confidence: 99%

“…4,5,8,9,18 Electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and electron back-scattering diffraction have been used to identify a range of intermetallic compounds that emerge during the coating transformation process, including the ternary Al-Fe-Si compounds commonly denoted τ 1 through τ 6 , and the binary phases η (Al 5 Fe 2 ), θ (Al 13 Fe 4 ), α 2 (AlFe), and ζ (Al 2 Fe). 4,8,17,19,20 The aluminum-rich corner of the ternary Al-Fe-Si phase diagram is complex, with numerous invariant reactions linking together three or more phases. 21,23,24 The gradual conversion of the Al-Si coating to a complete Al-Fe-Si intermetallic coating requires an increase in the Fe content of the coating, which means that the coating composition must change with time and temperature.…”

Section: ■ Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

2023

View full text Add to dashboard Cite

Hot-stamped ultrahigh strength steel components are pivotal to automotive light-weighting. Steel blanks, often coated with an aluminum-silicon (Al-Si) layer to protect them from oxidation and decarburization, are austenitized within a furnace and then simultaneously quenched and formed into shape. The Al-Si coating melts within the furnace and reacts with iron from the steel to yield an intermetallic phase that provides some long-term corrosion protection. During the intermediate liquid phase, some of the coating may transfer to the furnace components, leading to maintenance costs and operational downtime. A detailed understanding of the coating transformation mechanism is needed to avoid such production issues while ensuring that final intermetallic coatings conform to specifications. We introduce cross-sectional Raman microscopic mapping as a method to rapidly elucidate the coating transformation mechanism. Raman spectroscopic fingerprints for relevant intermetallic compounds were determined using synthesized Al-Fe-Si ternary and Al-Fe binary compounds. These fingerprints were used to map the spatial distribution of intermetallic compounds through cross sections of Al-Si-coated 22MnB5 specimens that were heated at temperatures between 570 and 900 °C. These chemical maps show that the intermetallic fraction of the coating does not grow significantly until formation of η (Al5Fe2) at the steel interface, suggesting that η facilitates extraction of iron from the steel and subsequent diffusion through the coating. Under the heating conditions used here, a series of reactions ultimately lead to a silicon-rich τ2 (Al3FeSi) phase on top of the binary η phase. The technique presented here simplifies structural analysis of intermetallic compounds, which will facilitate prototyping of strategies to optimize hot stamping.

show abstract

Section: ■ Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel

2023

View full text Add to dashboard Cite

show abstract

“…Figure4displays the chemical composition of the coating layer for each steel type corresponding to the holding time in the furnace at 1203 K. During the initial heating stage conducted for 150 s, the plating layer consisted of four inter-layers separated by an Al-Si-Fe diffusion layer. They include a superficial layer (Al 5 Fe 2 ), intermetallic layer (AlFe), intermediate layer (Al 5 Fe 2 ), and inter-diffusion layer[16]. As highlighted in Figure3a,b, the growth of the AlFe intermetallic layer due to the diffusion of Fe into the surface layer increases with the increase in the holding time of the heating furnace from 150 to 450 s for both the 1.5 and 1.8 GPa grade steel plates.…”

mentioning

confidence: 94%

Hydrogen Absorption and Desorption Behavior on Aluminum-Coated Hot-Stamped Boron Steel during Hot Press Forming and Automotive Manufacturing Processes

Kim

Jung

et al. 2021

Materials

View full text Add to dashboard Cite

Our study mainly focused on diffusible hydrogen in aluminum–silicon-coated hot-stamped boron steel during a hot press forming process and in pre-treatment sequential lines of the automotive manufacturing process using a thermal desorption spectroscopy (TDS) technique. First, in the hot stamping procedure, as the soaking time increased in the heating furnace at a specific dew point when austenitizing, a high concentration of diffusible hydrogen was absorbed into the hot-stamped boron steel. Based on the TDS analysis of hydrogen absorbed from hot stamping, the activation energy value of hydrogen trapping in 1.8 GPa grade steel is lower than that of 1.5 GPa grade steel. This means that diffusible hydrogen can be more easily diffused into defective sites of the microstructure at a higher level of the tensile strength grade. Second, in sequential pre-treatment lines of the automotive manufacturing process, additional hydrogen did not flow into the surface, and an electro-deposition process, including a baking procedure, was effective in removing diffusible hydrogen, which was similar to the residual hydrogen of the as-received state (i.e., initial cold rolled blank). Based on these results, the hydrogen absorption was facilitated during hot press forming, but the hydrogen was sequentially desorbed during automotive sequential lines on aluminum-coated hot-stamped steel parts.

show abstract