Bi-containing whisker material and preparation and growth inhibition method thereof

Abstract

The invention belongs to the technical field of new materials and new material preparation, and particularly relates to a Bi-containing whisker material and a preparation and growth inhibition method thereof, the components of the upper end and the lower end of a Bi-containing whisker are different, when the upper end is Bi, the lower end is Sn, and when the upper end is Sn, the lower end is Bi. The crystal whisker grows in a Cr-(Al, Sn, Bi)-B MAB phase solid solution region in a periodic lamellar structure. The preparation and growth inhibition method comprises the steps that Fe-Cr-B cast steel is subjected to hot dipping of Al-10Sn-4Si-xBi alloy (x is larger than 2 and smaller than 60 in percentage by mass), subsequent diffusion heat treatment is conducted, observation can be conducted through a scanning electron microscope after grinding and polishing are conducted, and when x is smaller than 15, Bi-containing whiskers can grow randomly; and when x is greater than 15, no whisker grows. The multi-component MAB phase solid solution can be prepared through a simple process, and the growth and inhibition method of the Bi-containing whisker is regulated and controlled, so that the variety of the MAB phase solid solution is expanded, and the variety of the whisker is enriched.

Description

Technical Field

[0001] The invention relates to the field of new materials, and in particular to a Bi-containing whisker material and a preparation method and growth inhibition method thereof. Background Art

[0002] In the applicant's previous research, it was found that the boride (Cr,Fe)2B will be generated in the structure of Fe-Cr-B cast steel with a certain Cr and B content, and when it reacts with aluminum liquid, it will generate a periodic lamellar structure (PLS) at the solid-liquid interface. The PLS is composed of FeAl3 and Cr-Al-B MAB phases arranged alternately. Elements such as Zn, Si, Sn in the aluminum liquid will significantly affect the composition of the Cr-Al-BMAB phase, and partially replace the Al atoms in the Cr-Al-B MAB phase to form a solid solution. The MAB phase is a special type of atomic layered compound, in which M is a transition metal element, A is a 13-16 group element, and B is a boron element. Among them, when hot-dip Al-Sn alloy is plated, Sn whiskers will also grow spontaneously in the Cr-(Al,Sn)-B MAB phase solid solution area formed. The MAB phase has certain similarities with another ternary layered compound MAX phase (X is C and N elements), but the structure and composition of the MAB phase are more complex. In fact, there are many reports on the spontaneous growth of A-site whiskers in the MAX phase, but they are mainly concentrated on Sn and In whiskers.

[0003] For MAB / MAX phase, Bi is also an A-position element. However, there are few reports on the synthesis of MAB / MAX phase containing Bi (especially MAB phase), and they mainly focus on the partial substitution of the A-position that occurs when the MAX phase reacts with the Pb-Bi eutectic melt to form a MAX phase solid solution containing Bi at the A-position. However, the growth of Bi-containing whiskers was not observed. In addition, for coatings such as Sn electroplating layers, Bi can also be used to inhibit the growth of Sn whiskers, but there are also contrary reports that Bi cannot inhibit the growth of Sn whiskers. In general, the effect of Bi on the electroplated Sn layer and the MAX phase is more complicated. At the same time, the effect of Bi on the MAB phase has not been reported. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a Bi-containing whisker material and a method for preparing and inhibiting the growth thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A Bi-containing whisker material, the upper end and the lower end of which have different compositions, when the upper end is Bi, the lower end is Sn; when the upper end is Sn, the lower end is Bi. The whisker grows in the Cr-(Al, Sn, Bi)-B MAB phase solid solution region in a periodic lamellar structure.

[0007] A method for preparing and inhibiting the growth of Bi-containing whiskers comprises the following steps:

[0008] (1) Hot-dip aluminum

[0009] The Fe-Cr-B cast steel containing boride (Cr,Fe)2B is hot-dip plated with Al-10Sn-4Si-xBi (mass percentage, the same below; 2<x<60) alloy, the aluminum alloy melt temperature is 750℃, the hot-dip plating time is 30 minutes, and after reaching the set time, it is taken out and air-cooled to room temperature;

[0010] (2) Diffusion heat treatment

[0011] The sample prepared in step (1) is placed in a muffle furnace for diffusion heat treatment, kept at 750°C for 1 hour, and cooled to room temperature with the furnace after reaching the set temperature. After grinding and polishing any surface of the obtained sample containing the coating, a scanning electron microscope can be used to observe that Bi-containing whiskers are randomly grown on the "white" Cr-Al-B phase area in the periodic lamellar structure.

[0012] A method for preparing a Bi-containing whisker material and inhibiting its growth, wherein the x value in the hot-dip Al-10Sn-4Si-xBi alloy is within the range of (2,60).

[0013] A method for preparing a Bi-containing whisker material and inhibiting its growth. Whether the Bi-containing whisker can grow is closely related to the x value: when x is less than 15, the Bi-containing whisker can grow; when x is greater than 15, the whisker cannot grow.

[0014] A method for preparing and inhibiting the growth of a whisker material containing Bi. The growth of a whisker with Bi at the upper end and Sn at the lower end and a whisker with Sn at the upper end and Bi at the lower end is random and has nothing to do with the size of the x value less than 15.

[0015] A method for preparing and inhibiting the growth of a Bi-containing whisker material. During the hot-dip aluminum plating-diffusion heat treatment process, (Cr,Fe)2B first reacts with Al liquid to generate a periodic lamellar structure consisting of alternating Cr-Al-B MAB phases and FeAl3, and then Sn and Bi simultaneously replace part of the Al atoms in the Cr-Al-B MAB phase and transform it into a Cr-(Al,Sn,Bi)-B MAB phase solid solution.

[0016] A method for preparing and inhibiting the growth of a Bi-containing whisker material. When x is less than 15, a nanometer-scale pure Sn phase and a pure Bi phase are generated on the grain boundary of a Cr-Al-B MAB phase.

[0017] A method for preparing and inhibiting the growth of a Bi-containing whisker material. When x is greater than 15, only a nanometer-scale pure Bi phase is generated on the grain boundary of a Cr-Al-B MAB phase.

[0018] A method for preparing and inhibiting the growth of a whisker containing Bi, wherein Al and Si elements in a hot-dip Al-10Sn-4Si-xBi alloy do not participate in the composition of the whisker.

[0019] A Bi-containing whisker material, wherein Bi in the Cr-(Al, Sn, Bi)-B MAB phase solid solution can increase the vacancy formation energy of Sn atoms.

[0020] The present invention provides a whisker material with complex components and a preparation method thereof, which has the following beneficial effects:

[0021] 1. Cr-(Al, Sn, Bi)-B MAB phase solid solution can be prepared by hot-dip coating of Fe-Cr-B cast steel with Al-10Sn-4Si-xBi alloy and subsequent diffusion heat treatment, which can transform the Cr-Al-B MAB phase in PLS into Cr-(Al, Sn, Bi)-BMAB phase solid solution. Moreover, after grinding and polishing, it is easy to observe that Bi-containing whiskers grow randomly on the Cr-(Al, Sn, Bi)-BMAB phase solid solution area;

[0022] 2. The composition of whiskers containing Bi can be divided into two types: (2) whiskers with Bi at the top and Sn at the bottom; (3) whiskers with Sn at the top and Bi at the bottom;

[0023] 3. The whisker growth behavior is related to the Bi content in the Al-10Sn-4Si-xBi alloy melt during hot-dip plating. When the Bi content in the aluminum alloy melt is greater than a certain critical value, the whisker growth behavior will be inhibited and whiskers will no longer grow.

[0024] 4. Cr-(Al,Sn,Bi)-B MAB phase solid solution was prepared by a simple method;

[0025] 5. The composition of the grown whiskers has nothing to do with the Si element in the Al-10Sn-4Si-xBi alloy melt;

[0026] 6. The types of MAB phases have been expanded and the types of whisker growth have been enriched. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0028] Figure 1 This is a cross-sectional microstructure diagram of the Fe-Cr-B cast steel prepared in Example 1 after hot-dip plating of Al-10Sn-4Si-3Bi alloy-diffusion heat treatment;

[0029] Figure 2 Cr element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 1 after hot-dip plating of Al-10Sn-4Si-3Bi alloy and diffusion heat treatment;

[0030] Figure 3 This is a Sn element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 1 after hot-dip coating with Al-10Sn-4Si-3Bi alloy and diffusion heat treatment;

[0031] Figure 4 Bi element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 1 after hot-dip coating of Al-10Sn-4Si-3Bi alloy and diffusion heat treatment;

[0032] Figure 5 This is a cross-sectional microstructure diagram of the Fe-Cr-B cast steel prepared in Example 2 after hot-dip plating with Al-10Sn-4Si-10Bi alloy and diffusion heat treatment;

[0033] Figure 6 Cr element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 2 after hot-dip plating with Al-10Sn-4Si-10Bi alloy and diffusion heat treatment;

[0034] Figure 7 This is the Sn element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 2 after hot-dip coating with Al-10Sn-4Si-10Bi alloy and diffusion heat treatment;

[0035] Figure 8 This is the Bi element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 2 after hot-dip plating of Al-10Sn-4Si-10Bi alloy and diffusion heat treatment.

[0036] Fig. 9 This is a cross-sectional microstructure diagram of the Fe-Cr-B cast steel prepared in Example 3 after hot-dip plating of Al-10Sn-4Si-17Bi alloy and diffusion heat treatment;

[0037] Fig.10 Cr element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 3 after hot-dip plating of Al-10Sn-4Si-17Bi alloy and diffusion heat treatment;

[0038] Fig.11 Sn element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 3 after hot-dip coating with Al-10Sn-4Si-17Bi alloy and diffusion heat treatment;

[0039] Fig.12This is the Bi element distribution diagram of the cross section of the Fe-Cr-B cast steel prepared in Example 3 after hot-dip coating with Al-10Sn-4Si-17Bi alloy and diffusion heat treatment. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0041] It is clear and complete that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Fe-Cr-B cast steel is prepared by the following method:

[0043] 1. Ingredients: According to the designed alloy composition, calculate the required weight of low-carbon ferrochrome Fe-58wt.%Cr-0.06wt.%C, Fe-18wt.%B master alloy and pig iron, the total weight is 10kg.

[0044] 2. Melting: The raw materials weighed in step ① are loaded into a vacuum melting furnace, and after being completely melted, they are superheated to 1600° C. and kept warm for 15 minutes, and then poured into a metal mold. After cooling, Fe-Cr-B cast steel is obtained.

[0045] The microstructure of the prepared Fe-Cr-B cast steel is mainly composed of gray-black (Cr,Fe)2B phase and gray-white α-Fe. The microstructure in the embodiment is photographed using a backscattered electron mode of a scanning electron microscope. The whiter the contrast, the larger the average atomic number.

[0046] Embodiment 1:

[0047] The prepared Fe-Cr-B cast steel was hot-dip plated with Al-10Sn-4Si-3Bi (mass percentage, the same below) alloy, the temperature of the aluminum alloy melt was 750℃, the immersion time was 30 minutes, and then it was taken out and air-cooled to room temperature; the sample of hot-dip plated Al-10Sn-4Si-3Bi alloy was placed in a muffle furnace for diffusion heat treatment, the temperature was 750℃, the time was 60 minutes, and it was cooled with the furnace. The sample was cut from the middle by wire cutting, and the metallographic specimen was prepared after grinding and polishing. The structure was observed by the backscattered electron mode of the scanning electron microscope. It was found that after hot-dip aluminum plating, a periodic lamellar structure composed of alternating FeAl3 and Cr-Al-B MAB phases was generated on the (Cr,Fe)2B / aluminum alloy melt interface. Among them, the Cr-Al-BMAB phase close to the outside showed a white contrast in the backscattered electron mode of the scanning electron microscope (representing that its average atomic number becomes larger, replaced by "whitening"), and Bi-containing whiskers can be randomly grown, such as Figure 1 As shown, combined Figure 2 Cr (representing the position of Cr-Al-B MAB phase) shown Figure 3 Sn shown, Figure 4 The Bi element distribution is shown in Figure 1. It can be seen that whiskers with Bi at the top and Sn at the bottom grow spontaneously on the "whitish" Cr-Al-B MAB phase area. The whitish Cr-Al-B MAB phase is caused by two factors: (1) the partial substitution of Sn and Bi for Al atoms in the Cr-Al-B MAB phase at position A to form a Cr-(Al,Sn,Bi)-B MAB phase solid solution; (2) pure Sn phase and pure Bi phase are dispersed on the grain boundaries of the Cr-Al-B MAB phase. The Si element in the hot-dip Al-Sn-Si-Bi alloy does not participate in the composition of whiskers, but can reduce the oxidation holes in the coating during the subsequent diffusion heat treatment process.

[0048] Embodiment 2:

[0049] The prepared Fe-Cr-B cast steel was hot-dip plated with Al-10Sn-4Si-10Bi alloy. The temperature of the aluminum alloy melt was 750℃ and the immersion time was 30 minutes. Then it was taken out and air-cooled to room temperature. The sample of hot-dip plated Al-10Sn-4Si-3Bi alloy was placed in a muffle furnace for diffusion heat treatment at a temperature of 750℃ for 60 minutes and then cooled with the furnace. The sample was cut in the middle by wire cutting, and a metallographic specimen was prepared after grinding and polishing. The structure was observed by the backscattered electron mode of a scanning electron microscope. It was found that after hot-dip aluminum plating, a periodic lamellar structure composed of alternating FeAl3 and Cr-Al-BMAB phases was generated at the (Cr,Fe)2B / aluminum alloy melt interface. Among them, the Cr-Al-B MAB phase close to the outside showed a white contrast in the backscattered electron mode of the scanning electron microscope (representing that its average atomic number becomes larger, replaced by "whitening"), and Bi-containing whiskers can be randomly grown, such as Figure 5 As shown, combined Figure 6 Cr (representing the position of Cr-Al-B MAB phase) shown Figure 7 Sn shown, Figure 8 The Bi element distribution is shown in Figure 1. It can be seen that whiskers with Sn at the top and Bi at the bottom grow spontaneously on the "whitish" Cr-Al-B MAB phase area. The whitish Cr-Al-B MAB phase is caused by two factors: (1) the partial substitution of Sn and Bi for Al atoms in the Cr-Al-B MAB phase at position A to form a Cr-(Al,Sn,Bi)-B MAB phase solid solution; (2) pure Sn phase and pure Bi phase are dispersed on the grain boundaries of the Cr-Al-B MAB phase. The Si element in the hot-dip Al-Sn-Si-Bi alloy does not participate in the composition of whiskers, but can reduce the oxidation holes in the coating during the subsequent diffusion heat treatment process.

[0050] Embodiment 3:

[0051] The prepared Fe-Cr-B cast steel was hot-dip plated with Al-10Sn-4Si-17Bi alloy. The temperature of the aluminum alloy melt was 750°C and the immersion time was 30 minutes. Then it was taken out and air-cooled to room temperature. The sample of hot-dip plated Al-10Sn-4Si-3Bi alloy was placed in a muffle furnace for diffusion heat treatment at a temperature of 750°C for 60 minutes and then cooled with the furnace. The sample was cut in the middle by wire cutting, and a metallographic specimen was prepared after grinding and polishing. The structure was observed by the backscattered electron mode of a scanning electron microscope. It was found that after hot-dip aluminum plating, a periodic lamellar structure composed of alternating FeAl3 and Cr-Al-BMAB phases was generated at the (Cr,Fe)2B / aluminum alloy melt interface. Among them, the Cr-Al-B MAB phase close to the outside showed a white contrast in the backscattered electron mode of the scanning electron microscope (representing that its average atomic number becomes larger, replaced by "whitening"), but no whiskers grew, such as Fig. 9 As shown. Combined Fig.10 Cr (representing the position of Cr-Al-B MAB phase) shown Fig.11 Sn shown, Fig.12 From the Bi element surface distribution shown, it can be seen that the whitish Cr-Al-BMAB phase caused by Sn and Bi is still formed. The whitish Cr-Al-B MAB phase is caused by two factors: (1) the partial replacement of Al atoms in the Cr-Al-BMAB phase by Sn and Bi at the A position forms the Cr-(Al,Sn,Bi)-B MAB phase solid solution; (2) the pure Bi phase is dispersed on the grain boundary of the Cr-Al-B MAB phase. The Si element in the hot-dip Al-Sn-Si-Bi alloy does not participate in the composition of whiskers, but can reduce the oxidation holes in the coating during the subsequent diffusion heat treatment process.

[0052] The above embodiments are only preferred technical solutions of the invention and should not be regarded as limitations of the invention. The protection scope of the invention should be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the invention.

Claims

1. A Bi-containing whisker material, characterized in that: The upper and lower ends of the Bi-containing whiskers have different compositions: when the upper end is Bi, the lower end is Sn; when the upper end is Sn, the lower end is Bi. The whiskers grow in the Cr-(Al, Sn, Bi)-BMAB phase solid solution region in the periodic lamellar structure.

2. The method for preparing and inhibiting the growth of Bi-containing whiskers according to claim 1, characterized in that: The following steps are involved: (1) Hot-dip aluminum Fe-Cr-B cast steel containing boride (Cr,Fe)2B was hot-dip plated with Al-10Sn-4Si-xBi (mass percentage, the same below; 2<x<60) alloy, the aluminum alloy melt temperature is 750℃, the hot dip coating time is 30 minutes, and after reaching the set time, it is taken out and air cooled to room temperature; (2) Diffusion heat treatment The sample prepared in step (1) is placed in a muffle furnace for diffusion heat treatment, kept at 750°C for 1 hour, and cooled to room temperature with the furnace after reaching the set temperature. After grinding and polishing any surface of the obtained sample containing the coating, a scanning electron microscope can be used to observe that Bi-containing whiskers are randomly grown on the "white" Cr-Al-B phase area in the periodic lamellar structure.

3. The method for preparing and inhibiting the growth of a Bi-containing whisker material according to claim 2, characterized in that: The x value in the hot-dip Al-10Sn-4Si-xBi alloy is in the range of (2,60).

4. The method for preparing and inhibiting the growth of a Bi-containing whisker material according to claim 2, characterized in that: Whether Bi-containing whiskers can grow is closely related to the x value: when x is less than 15, Bi-containing whiskers can grow; when x is greater than 15, whiskers cannot grow.

5. The method for preparing and inhibiting the growth of a Bi-containing whisker material according to claim 2, characterized in that: The growth of the whiskers with Bi at the top and Sn at the bottom and the whiskers with Sn at the top and Bi at the bottom is random and has nothing to do with the value of x less than 15.

6. The method for preparing and inhibiting the growth of a Bi-containing whisker material according to claim 2, characterized in that: During the hot-dip aluminum-diffusion heat treatment process, (Cr,Fe)2B first reacts with Al liquid to form a periodic lamellar structure composed of alternating Cr-Al-B MAB phase and FeAl3, and then Sn and Bi simultaneously partially replace the Al atoms in the Cr-Al-B MAB phase and transform it into a Cr-(Al,Sn,Bi)-B MAB phase solid solution.

7. The method for preparing and inhibiting the growth of a Bi-containing whisker material according to claim 2, characterized in that: When x is less than 15, nanoscale pure Sn phase and pure Bi phase are also generated on the grain boundary of the Cr-Al-B MAB phase.

8. The method for preparing and inhibiting the growth of a Bi-containing whisker material according to claim 2, characterized in that: When x is greater than 15, only nanoscale pure Bi phase is generated on the grain boundary of Cr-Al-B MAB phase.

9. The method for preparing and inhibiting the growth of Bi-containing whiskers according to claim 2, characterized in that: The Al and Si elements in the hot-dip Al-10Sn-4Si-xBi alloy do not participate in the composition of whiskers.

10. The Bi-containing whisker material according to claim 1, characterized in that: Bi in the Cr-(Al,Sn,Bi)-B MAB phase solid solution can increase the vacancy formation energy of Sn atoms.

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