A material generating a solid solution phase mab at a position a, a preparation method and application thereof

Abstract

The application belongs to the field of new materials, and discloses a material generating A-site solid solution MAB phase and a preparation method and application thereof, wherein the A-site solid solution MAB phase is a Cr-(Al,Zn)-B phase. Fe-Cr-B cast steel is subjected to hot-dip aluminizing, and the composition of the aluminum liquid is Al-8.9Si alloy, and then the Fe-Cr-B cast steel containing the Al-Si alloy plating layer is placed in ZnCl2 molten salt for corrosion. The Cr-(Al,Zn)-B MAB phase containing the A-site solid solution can be generated through a simple process, and then the corrosion of the chloride molten salt is blocked.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new materials, in particular to a material generating A-site solid solution MAB phase and a preparation method and application thereof. BACKGROUND

[0002] MAB phase (M=transition group metal element, A=Al, Zn, Si, etc., and B is B element) is a ternary layered intermetallic compound. MAB phase has both metal and ceramic properties and is of great concern. Existing reports on MAB phase mainly focus on the preparation of MoAlB, Fe2AlB2 and MAB phase solid solution alloyed with M site (such as Mo 4 / 3 Y 2 / 3AlB2, Mo 4 / 3 Sc 2 / 3 AlB2) by complex powder metallurgy process. At the same time, the elements in A site are mainly Al, and the synthesized A-site solid solution mainly contains Al, Si, Ga, etc. (such as MoAl 1-x Si x B). The method requires a high temperature (above 1000℃) and is prone to generate M-A and M-M' competing phases. In recent years, Cr-Al-B MAB phase has gradually attracted the attention of scholars, but there are few reports on M and A-site solid solution, especially the formation of A-site solid solution, which is mainly concentrated in Al element. The binding force between A layer atoms and M and B atoms in MAB phase is weak, which is theoretically prone to de-embedding under certain conditions, which provides the possibility for the preparation of A-site solid solution. SUMMARY

[0003] In view of the problems existing in the prior art, the purpose of the present application is to provide a material generating A-site solid solution MAB phase and a preparation method and application thereof.

[0004] The alloy can improve corrosion resistance, thereby achieving the effect of protecting the substrate. To solve the above technical problems, the technical scheme adopted by the present application is as follows: an A-site solid solution MAB phase, the MAB phase is a Cr-(Al, Zn)-B phase, and the A site is an Al-Zn solid solution. The present application also provides a preparation method of the A-site solid solution MAB phase, comprising the following steps:

[0005] Step one: preparing Fe-Cr-B cast steel, the prepared Fe-Cr-B cast steel composition is Fe-(30-40) wt. % Cr-(6-9) wt. % B-0.05 wt. % C.

[0006] Step 2: The Fe-Cr-B cast steel prepared in Step 1 is immersed in Al-8.9Si alloy melt for hot-dip aluminizing. After a certain reaction time, the sample is quickly removed from the aluminum melt and air-cooled to obtain Fe-Cr-B cast steel with a residual aluminum layer on the surface. At the interface of the boride (Cr, Fe)2B / Al melt in the Fe-Cr-B cast steel, a periodic lamellar structure composed of Cr-Al-B MAB phase and FeAl3 is generated.

[0007] Step 3: Perform diffusion annealing on the sample prepared in Step 2 at a temperature of 750℃ for 1 hour.

[0008] Step 4: Immerse the sample prepared in Step 3 into ZnCl2 molten salt at 350-550℃ for a certain period of time and then remove it to obtain the Cr-(Al, Zn)-B MAB phase containing solid solution at position A.

[0009] Preferably, in step two, the Al atoms of the Cr-Al-B MAB phase generated are partially replaced by Zn atoms in step three to form the Cr-Al-B MAB phase of the A-position solid solution.

[0010] Preferably, the residual aluminum layer covering the outer side of the Cr-Al-B MAB phase generated in step two undergoes a displacement reaction with ZnCl2 molten salt in step four to generate a Zn solid phase and an AlCl3 gas phase.

[0011] Preferably, the Zn generated by the substitution reaction that occurs first in step four forms a eutectic liquid phase with Al in the Cr-Al-B MAB phase and accelerates the substitution of Al atoms in the Cr-Al-B MAB phase by Zn atoms.

[0012] Preferably, in step four, Zn in the molten salt further occurs. 2+ It reacts with the Cr-Al-B MAB phase and partially replaces the Al atoms therein.

[0013] Preferably, the substitution rate of Zn atoms for Al atoms at position A increases with the extension of corrosion time.

[0014] Preferably, the Zn or Zn 2+ Before undergoing a substitution reaction with Al in the Cr-Al-B MAB phase, it needs to diffuse through the FeAl3 phase in the periodic lamellar structure.

[0015] Preferably, after partially replacing Al atoms in the Cr-Al-B MAB phase, Zn grows in elemental form from the interstitial space of the Cr-(Al,Zn)-B phase into the adjacent FeAl3 phase.

[0016] This invention also provides a method for preparing an A-site solid solution MAB phase and its application in ZnCl2 molten salt corrosion resistant materials. The generated A-site MAB phase can block molten salt corrosion during the corrosion process and is continuously generated at the interface with Fe-Cr-B cast steel.

[0017] The present invention provides a material for generating a MAB phase solid solution at position A, a method for its preparation, and its application, which have the following advantages compared to the prior art:

[0018] 1. A Cr-(Al, Zn)-B MAB phase with an A position of (Al, Zn) solid solution was prepared by hot-dip aluminizing, diffusion annealing and ZnCl2 molten salt etching.

[0019] 2. When hot-dip aluminizing, Al-8.9Si alloy melt is used. The high Si content can significantly improve the oxidation resistance of the coating, thereby improving the coating's resistance to molten salt corrosion.

[0020] 3. A Cr-(Al, Zn)-B MAB phase with a high substitution rate can be obtained. The substitution rate of Zn atoms for Al atoms at position A in the Cr-Al-B phase increases with the extension of corrosion time and the increase of molten salt temperature.

[0021] 4. The outer side of the coating is corroded by molten salt. The Cr-Al-B MAB phase is corroded by molten salt and undergoes a displacement reaction at the A site. On the other hand, it can also block molten salt corrosion. The coating / steel interface still exhibits self-growth characteristics during the ZnCl2 molten salt corrosion process at 350-550℃. Attached Figure Description

[0022] Figure 1 This is a cross-sectional microstructure of the periodic lamellar structure formed after hot-dip aluminizing and diffusion annealing in Example 1.

[0023] Figure 2 The image shows the cross-sectional microstructure of the hot-dip aluminized-diffusion heat-treated ZnCl2 molten salt sample prepared in Example 1 after corrosion.

[0024] Figure 3 This is a cross-sectional Zn element distribution diagram of PLS ​​containing the Cr-Al-B MAB phase after ZnCl2 molten salt corrosion in Example 1.

[0025] Figure 4 The image shows the cross-sectional microstructure of the hot-dip aluminized-diffusion heat-treated ZnCl2 molten salt sample prepared in Example 2 after corrosion.

[0026] Figure 5 for Figure 4 High magnification morphology of the whitish Cr-Al-B MAB phase. Implementation

[0027] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0028] The Fe-Cr-B cast steel in the examples was prepared by the following method.

[0029] Ingredients: Based on the designed alloy composition, calculate the required weight of micro-carbon ferrochrome Fe-36.6wt.%Cr-0.06wt.%C, Fe-8.8wt.%B, intermediate alloy, and pig iron, with a total weight of 10kg.

[0030] Melting: The weighed raw materials from step ① are loaded into a vacuum melting furnace. After they are completely melted, they are poured into a metal mold to obtain Fe-Cr-B cast steel.

[0031] The microstructures in the examples were captured using a scanning electron microscope in backscatter mode. The darker the contrast, the smaller the average atomic number. The elemental surface distribution was determined using an electron probe microanalyzer, which can accurately measure element B. Example 1:

[0032] Fe-Cr-B cast steel with Fe-37 wt.% Cr-9 wt.% B-0.1 wt.% C was prepared, and its microstructure consisted of α-Fe and (Cr, Fe)2B.

[0033] After sampling the prepared Fe-Cr-B cast steel, it was hot-dip aluminized with Al-8.9%Si at a temperature of 750℃ for 30 minutes. After hot-dip aluminizing with Al-Si alloy, the Fe-Cr-B cast steel will form a periodic lamellar structure containing the Cr-Al-B MAB phase at the interface of the (Cr,Fe)2B / Al-Si alloy melt.

[0034] The sample was placed in a muffle furnace for diffusion annealing at 750℃ for 60 minutes, followed by furnace cooling. The microstructure of the sample after diffusion annealing was observed, such as... Figure 1 As shown, the sample exhibits better antioxidant properties due to the addition of Si.

[0035] The diffusion-annealed sample was immersed in ZnCl2 molten salt at 350℃ for 30 minutes for etching, then removed, mounted, and a metallographic sample was prepared. The cross-sectional microstructure was then observed. Figure 2 As shown, the Cr-Al-B MAB phase in the periodic lamellar structure of the corroded area exhibits a whitening phenomenon. The elemental distribution was then analyzed using an electron probe microanalysis system. The distribution of Zn is shown in the figure below. Figure 3 As shown, the whitish areas have a higher Zn content, while the non-whitish areas have a lower Zn content. Example 2:

[0036] Fe-Cr-B cast steel with Fe-35 wt.% Cr-6 wt.% B-0.1 wt.% C was prepared, and its microstructure consisted of α-Fe and (Cr, Fe)2B.

[0037] The prepared Fe-Cr-B cast steel was immersed in an Al-8.9Si alloy melt for hot-dip galvanizing at a temperature of 750°C for 60 minutes. After the time was up, the steel was removed and cooled to room temperature in air.

[0038] The sample was placed in a muffle furnace for diffusion heat treatment at 750°C for 60 minutes, and then cooled with the furnace.

[0039] After diffusion annealing, the sample was immersed in ZnCl2 molten salt at 400℃ for 60 minutes for etching. It was then removed, mounted, and a metallographic sample was prepared. The cross-sectional microstructure was observed. Figure 4 As shown, the periodic lamellar structure regions gradually turn white from the outside in. Figure 5 The high-magnification morphology of the whitish periodic lamellar structure region shows that the whitishness occurs at the Cr-Al-B MAB phase position within the periodic lamellar structure. Example 3:

[0040] Fe-Cr-B cast steel with Fe-37 wt.% Cr-9 wt.% B-0.1 wt.% C was prepared, and its microstructure consisted of α-Fe and (Cr,Fe)2B.

[0041] The prepared Fe-Cr-B cast steel was immersed in Al-8.9Si alloy melt for hot-dip galvanizing reaction at a melt temperature of 750℃ for 30 minutes.

[0042] The sample was placed in a muffle furnace for diffusion heat treatment at 750°C for 60 minutes, and then cooled with the furnace.

[0043] After diffusion annealing, the sample was immersed in ZnCl2 molten salt at 350℃ for 60 minutes for etching. After removal, the sample was mounted to prepare a metallographic sample and its cross-sectional microstructure was observed.

[0044] The above-described specific embodiments are preferred embodiments of the present invention and are not intended to limit the present invention. Any other changes or equivalent substitutions made without departing from the technical solution of the present invention are included within the protection scope of the present invention.

Claims

1. An A-site solid solution MAB phase, characterized in that, The MAB phase is Cr-(Al, Zn)-B phase, and the A site is Al-Zn solid solution; The preparation method of the A site solid solution MAB phase comprises the following steps: Step one, hot-dip aluminum plating Fe-(30-40) wt. % Cr-(6-9) wt. % B-0.05 wt. % C cast steel is immersed into an Al-8.9Si alloy melt for hot-dip aluminum plating, and after a certain reaction time, the sample is quickly taken out of the aluminum liquid, and air-cooled to obtain a Fe-Cr-B cast steel with a residual aluminum layer attached to the surface, and a periodic lamellar structure composed of Cr-Al-B MAB phase and FeAl3 is generated on the interface between the boride (Cr, Fe) 2B / Al-Si alloy melt in the Fe-Cr-B cast steel; Step two, diffusion annealing The sample prepared in step one is subjected to diffusion annealing at a temperature of 750 DEG C for 1 h; Step three, ZnCl2 molten salt corrosion The sample prepared in step two is immersed in a ZnCl2 molten salt at 350-550 DEG C for a certain time, and then taken out to obtain a Cr-(Al, Zn)-B MAB phase containing an A site solid solution.

2. The A-site solid solution MAB phase of claim 1, wherein, The Al atoms in the Cr-Al-B MAB phase generated in step one are partially replaced by Zn atoms in step three to form a Cr-(Al, Zn)-B MAB phase with A site solid solution.

3. The A-site solid solution MAB phase of claim 1, wherein, The residual aluminum layer covering the outside of the Cr-Al-B MAB phase generated in step one reacts with the ZnCl2 molten salt in step three to generate pure Zn solid phase and AlCl3 gas phase.

4. The A-site solid solution MAB phase of claim 1, wherein, In step three, the Zn generated by the initial replacement reaction forms a eutectic liquid phase with Al in the Cr-Al-B MAB phase and accelerates the replacement of Al atoms in the Cr-Al-B MAB phase by Zn atoms.

5. The A-site solid solution MAB phase of claim 1, wherein, The step three subsequently also occurs in the molten salt Zn 2+ reacts with the Cr-Al-B MAB and partially replaces the Al atoms therein.

6. The A-site solid solution MAB phase of claim 1, wherein, The replacement rate of Zn atoms for Al atoms at the A site increases with the extension of the ZnCl2 molten salt corrosion time and the increase of the temperature.

7. The A-site solid solution MAB phase of claim 1, wherein: Zn or Zn 2+ Before the displacement reaction with the Al in the Cr-Al-BMAB, diffusion through the FeAl3 phase in the periodic lamellar structure is required.

8. The A site solid solution MAB phase of claim 1, wherein, After completing the partial replacement of Al atoms in the Cr-Al-B MAB phase, Zn grows in the form of an element from the interstice of the Cr-(Al, Zn)-B phase to the adjacent FeAl3 phase.

9. The use of an A-site solid solution MAB phase according to any one of claims 1 to 8 in a material resistant to corrosion by molten ZnCl2, characterized in that, The MAB phase blocks the molten salt corrosion during the corrosion process and continuously generates on the interface in contact with the Fe-Cr-B cast steel.

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