Microstructural Evolution of Intermetallic Compound Formed in Boron Steel Hot-Dipped in Al–7%Ni Alloy

Abstract

Abstract:The microstructural evolution of the intermetallic compound (IMC) layer formed on and in boron steel that was hot dipped in an Al-7Ni (wt %) bath at 690 • C for 30-180 s was investigated, and the growth mechanism of the IMC was identified. Except for the solidification structure of Al, the reaction layer consisted of one layer on the steel surface and two layers in the steel interior. The reaction phase formed on the original surface of the steel was the Al 9 FeNi (T) phase, which has a monoclinic (space group: P21/c) crystal structure. The reaction phase formed from the T phase was the Fe 2 Al 5 (η) phase, which is orthorhombic (space group: Cmcm). The variation in thickness of the η phase increased linearly with increasing dipping time, which is in accordance with the diffusion growth, a growth mechanism of the η phase in Al-coated pure Fe and low-carbon steels. The Fe 3 AlC (κ) phase (which had a band shape with a width of 100 nm) and a cubic system were formed along the interface between the Fe2Al5 (η) phase and the steel.

Study on the Formation of Reaction Phase to Si Addition in Boron Steel Hot-Dipped in Al–7Ni Alloy

“…This is considered beneficial in laser welding. This is the same as the result of the study on the Al-7Ni wt % coating layer that did not contain Si [10]. As shown in Table 3, Nos.…”

“…In Figure 2a, the Si-free specimen, the R1 layer (No. 4-1) existing between the C layer and the steel structure (S) was formed on the surface of the base material as seen in previous research results [10]. It is suggested that the Al9FeNi (T) phase is formed by the reaction.…”

“…In Figure 2b Figure 2a is the Fe 2 Al 5 (η) intermetallic compound, which is a reaction layer made by diffusion of Al. This layer is a coating composition to the base metal as observed from the previous research results [10], SEM images, and EDS component analyses. This is compared with the chemical compositions of the R2 layer of the Si-added specimens: Nos.…”

“…This causes the tensile strength and the collision characteristics to degrade [6][7][8][9]. To solve this problem, various previous studies have developed the Al-7Ni wt % multifunctional coating [10]. It is based on the Al-Ni coating, which is known to have a higher oxidation resistance at high temperatures compared to Al coating [11], and an appropriate amount of austenite stabilizing element is added to the coating to prevent ferrite and Fe-Al-type IMC formation.…”

Hot-Dip Aluminizing on AISI F55–UNS S32760 Super Duplex Stainless Steel Properties: Effect of Thermal Treatments

“…Further, it allows the identification of the intermetallic compounds generated at the interface between the SDSS substrate and the aluminum external layer as: Al-Me 3 , Al-Me 2 , Al-Me, Al 7 -Me, Al 3 -Me ( Figure 11 and Table 3). The detected phases also display the same morphology of those identified in the literature [11,55,56].…”