CN112522548B

CN112522548B - Wear-resistant Mg-containing aluminum-tin bearing bush alloy

Info

Publication number: CN112522548B
Application number: CN202011232492.9A
Authority: CN
Inventors: 吴晓蓝; 王冬梅; 王为; 文胜平; 高坤元; 黄晖; 魏午; 聂祚仁
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2020-11-06
Filing date: 2020-11-06
Publication date: 2022-07-12
Anticipated expiration: 2040-11-06
Also published as: CN112522548A

Abstract

A wear-resistant Mg-containing aluminum-tin bearing bush alloy belongs to the technical field of metal alloy materials. The Mg-containing aluminum-tin bearing bush alloy comprises, by weight, 8-12% of Sn, 2.5-4% of Si, 0.5-1.5% of Mg, and the balance of Al and inevitable impurity elements. According to the invention, a small amount of Mg element is added into the Al-Sn bearing alloy, so that the microstructure of the alloy is obviously refined, the hardness of the Al-Sn bearing alloy is improved by about 12%, the abrasion loss under a large load is reduced by about 20%, and the abrasion loss under a small load is reduced by about 30%.

Description

Wear-resistant Mg-containing aluminum-tin bearing bush alloy

Technical Field

The invention belongs to the technical field of metal alloy materials, and particularly relates to a wear-resistant Mg-containing aluminum-tin bearing bush alloy.

Background

The aluminum-based bearing bush alloy has high strength-to-weight ratio, good corrosion resistance, seizure resistance and the like, and is one of common metal-based bearing bush materials. Among them, Al-Sn bearing alloy is one of the most promising aluminum-based bearing alloy because of its good wear resistance and friction reduction and no toxicity. Al-Sn alloys belong to a typical mutually insoluble system, Sn has a very low solid solubility in an aluminum matrix, and Sn element in the alloys exists mainly in a beta (Sn) phase. On the one hand, the beta (Sn) phase is soft and has good deformation coordination with the aluminum matrix in the deformation process, so that the alloy has good processing performance. On the other hand, during the friction process, the temperature of the friction surface can be increased, the low melting point beta (Sn) phase can be softened and even melted, and the low melting point beta (Sn) phase can be used as a lubricant under the condition that the lubricating oil fails, so that the alloy has good wear resistance and friction reduction performance. The Al-Sn bearing alloy is divided into a high-tin alloy (the Sn content is 15-25 wt.%), a medium-tin alloy (the Sn content is 8-14 wt.%), and a low-tin alloy (the Sn content is 6-7 wt.%), according to the difference of the Sn content. The medium tin alloy has good compliance, embeddability and seizure resistance, higher bearing capacity and better wear resistance, and is most widely applied.

With the continuous improvement of mechanical efficiency, the engine is also developed towards the standard of high rotating speed, high load, miniaturization and light weight, so that higher requirements are placed on the comprehensive performance of the bearing bush alloy, and the improvement of the bearing capacity, the wear resistance and the friction reduction of the Al-Sn bearing bush alloy becomes one of important research directions. The Al-Sn alloy is added with elements, and the microstructure of the alloy can be effectively regulated and controlled by combining reasonable process treatment, so that the performance of the alloy is improved. By adding 1-4 wt.% of Si element to the alloy and carrying out reasonable heat treatment on the alloy, a beta (Sn) Si-in-Si "peritectic structure can be formed in the alloy, and no other compound is generated. In the 'beta (Sn) -Si-coated' structure, the beta (Sn) phase of the outer layer is beneficial to improving the surface performance of the alloy, so that the alloy has good seizure resistance, embeddability and compliance; the Si particles of the core are beneficial to improving the hardness and the strength of the alloy and improving the wear resistance of the alloy. The beta (Sn) phase may also delay the propagation of cracks initiated at its interface with the Si particles during deformation. It is worth noting that the content of Sn and Si elements in the alloy has a great influence on the formation of the structure, when the value of Sn/Si is between 3 and 4, the beta (Sn) coated Si structure in the Al-Sn-Si alloy has the largest volume fraction and is distributed uniformly, and the alloy has the best tribological performance.

Mg has larger solid solubility in aluminum matrix, and the addition of Mg element in Al-Sn alloy can improve the hardness of the alloy matrix through solid solution strengthening on one hand, and on the other hand, the Mg element and Sn element in the alloy are easy to form Mg₂The Sn phase can enhance the hardness of the alloy by strengthening the second phase. In addition, because the Sn-Mg eutectic structure of the Sn-rich end has a lower melting point, the Sn-Mg eutectic structure can be softened or melted due to the temperature rise in the friction process, and the alloy has better surface performance.

Disclosure of Invention

The invention mainly aims to design reasonable components of the Al-Sn-Si alloy, so that the value of Sn/Si is 3-4, a small amount of Mg element is added into the alloy, the microstructure of the alloy is regulated and controlled by combining a reasonable heat treatment process, and a uniformly distributed peritectic structure is formed, so that the hardness, the strength and the tribological performance of the alloy are improved.

The wear-resistant Mg-containing aluminum-tin bearing bush alloy is characterized in that: the weight percentage of each component is that Sn accounts for 8-12%, Si accounts for 2.5-4%, Mg accounts for 0.5-1.5%, and the balance is Al and inevitable impurity elements; keeping the temperature of the alloy at 479-490 ℃ for 3.5-4.5 hours, and regulating and controlling the microstructure of the alloy to be a uniformly distributed peritectic structure.

The specific preparation process and the heat treatment process are as follows:

designing reasonable alloy components, weighing and proportioning pure aluminum, pure tin, pure magnesium and Al-21Si (wt.%) intermediate alloy according to the designed weight percentage, putting the pure aluminum and the Al-Si intermediate alloy into a smelting furnace for melting, adding the pure tin and the pure magnesium wrapped by aluminum foil after the pure aluminum and the Al-Si intermediate alloy are completely melted, removing slag and stirring after tin blocks and magnesium blocks are melted, pouring at a temperature range of 760-820 ℃, cooling by water, and preserving the temperature of an ingot for 3.5-4.5 hours at a temperature range of 470-490 ℃.

Observing the microstructure of the homogenized alloy, and measuring the mechanical property and the tribological property of the alloy.

The addition of a small amount of Mg element increases the hardness of the Al-Sn bearing alloy by about 12%, reduces the wear under large load by about 20%, and reduces the wear under small load by about 30%, based on solid solution strengthening and second phase strengthening.

The outstanding substantive features and remarkable progress of the technical scheme of the invention are mainly reflected in that:

1. based on the influence of Sn, Si content and Sn/Si value on the structure and performance of the alloy, Al-Sn-Si alloy components are designed, and a small amount of Mg element is added into the alloy material, so that the mechanical property, the wear resistance and the friction reduction performance of the alloy are further improved.

2. A heat treatment system of preserving heat for 3.5-4.5 hours at 470-490 ℃ is adopted to regulate and control the microstructure structure of the Al-Sn-Si-Mg alloy, and a peritectic structure beneficial to improving the mechanical property and the tribological property of the alloy is successfully formed.

Drawings

FIG. 1 is a 1000-fold magnified image of backscattered electrons of a homogenized Al-12Sn-4Si-1.5Mg alloy at 480 ℃ for 4 hours in an example;

FIG. 2 is a 10000 times magnified image of the back scattered electron of the homogenized Al-12Sn-4Si-1.5Mg alloy which is insulated for 4 hours at 480 ℃ in the example;

FIG. 3 is a 1000-fold magnified image of backscattered electrons of the homogenized Al-12Sn-4Si alloy in the comparative example, held at 480 ℃ for 4 hours;

FIG. 4 is a graph comparing the wear of two Al-Sn bearing shell alloys under high load.

FIG. 5 is a graph comparing the wear of two Al-Sn bearing shell alloys under small loads.

Detailed Description

The present invention will be described in detail below with reference to the drawings and specific embodiments, but the present invention is not limited to the following examples.

Examples

The newly designed Al-Sn bearing bush alloy comprises the following components in percentage by weight: 12% of Sn, 4% of Si, 1.5% of Mg, and the balance of Al and inevitable impurities.

(1) Proportioning according to designed alloy components, putting the proportioned high-purity aluminum and Al-12Si (wt.%) intermediate alloy into a graphite crucible, putting the graphite crucible into a smelting furnace, closing a furnace door, regulating the furnace temperature to 800 ℃, and preserving heat.

(2) After melting pure aluminium and Al-Si intermediate alloy, removing slag and stirring, putting pure tin and pure magnesium wrapped by aluminium foil into the molten liquid, after melting, removing slag and stirring again, pouring the molten metal into iron mould for casting, and cooling by water. The actual weight percentages of the elements of the smelted bearing bush alloy are as follows: 11.44% of Sn, 4.61% of Si, 1.57% of Mg, and the balance of Al and inevitable impurities.

(3) And preserving the heat of the cast ingot at 480 ℃ for 4 hours, and cooling by water.

(4) The homogenized alloy was cut into 2cm × 1cm × 0.5cm pieces by wire cutting, polished with #400, #800, #1000, #1500, #2000, #3000 sandpaper and a polishing paste having a particle size of W1.5, rinsed with alcohol, and ultrasonically cleaned for 4 minutes.

(5) And (4) measuring the hardness of the homogenized alloy, testing the same sample for nine times, and taking an average value. The alloys were subjected to tensile testing, twice for each sample. And (3) performing tribology test on the alloy by adopting a CFT-I type material surface property comprehensive tester at room temperature. GCr15 bearing steel balls with the diameter of 5mm are used as friction pairs, the loads applied by friction are respectively 30N, 50N and 70N, the running speed is 300t/m, the sliding length is 5mm, the friction duration is 15min, no lubricating oil exists, and the abrasion loss of a friction experiment is shown in a figure.

Comparative example

The newly designed Al-Sn bearing bush alloy comprises the following components in percentage by weight: 12% of Sn, 4% of Si, and the balance of Al and unavoidable impurities.

(2) After melting pure aluminium and Al-Si intermediate alloy, removing slag and stirring, putting pure tin and pure magnesium wrapped by aluminium foil into the molten liquid, after melting, removing slag and stirring again, pouring the molten metal into iron mould for casting, and cooling by water. The actual weight percentages of the elements of the smelted bearing bush alloy are as follows: 12.12% of Sn, 4.05% of Si, 1.57% of Mg, and the balance of Al and inevitable impurities.

(5) The hardness of the homogenized alloy was measured, and the same sample was tested nine times to obtain the average value. And (3) performing friction test on the alloy by adopting a CFT-I type material surface property comprehensive tester at room temperature. GCr15 bearing steel balls with the diameter of 5mm and alloy samples are used as friction pairs, the loads applied by friction are respectively 30N, 50N and 70N, the running speed is 300t/m, the sliding length is 5mm, the friction time is 15min, and no lubricating oil exists. And measuring the mass of the alloy sample before and after abrasion by using a constant-base balance, and finally determining the mass abrasion of the alloy. The wear amount of the friction test is shown in fig. 4 and 5.

Analysis of the microstructure of the example alloy in the backscattered electron images 1, 2 gives: after heat treatment for 4 hours at 480 ℃, beta (Sn) coated Si or Mg with dispersed and uniform distribution is formed in the alloy of the embodiment₂Sn comprises Si "island or spherical structures, as shown by a in image 1. The white contrast phase is beta (Sn) phase with large atomic number, and the stripe or dot gray contrast phase distributed on the beta (Sn) phase is Mg₂Sn, Si particles in which a black contrast phase distributed at the core of an island-like or spherical structure and at the boundary of an aluminum matrix is adjacent to Al in atomic number.

Analysis of the microstructure of the comparative example in the back-scattered electron image 3 gives: after heat treatment at 480 ℃ for 4 hours, island-shaped or spherical structures of 'beta (Sn) coated Si' with uniform distribution are formed in the alloy, as shown in A in image 3. The white contrast phase is a beta (Sn) phase with a larger atomic number, and the near-black contrast phase distributed at the core of an island-shaped or spherical structure and at the boundary of an aluminum matrix is Si particles with an atomic number adjacent to Al.

Comparing the microscopic structures of the backscattered electron image 1 and the image 3, it can be seen that the example alloy added with 1.5Mg has smaller grain size than the comparative alloy, and island-shaped or spherical structures in the example alloy are distributed more uniformly and have smaller size.

Comparing the wear loss of the two Al-Sn bearing alloys in the image 4 under a large load, the example alloy containing Mg has smaller wear loss under different loads, and compared with the comparative alloy, the wear quality of the example alloy is respectively reduced by about 19%, 20% and 20% at 30N, 50N and 70N, which shows that the example alloy has better wear resistance, and the addition of a proper amount of Mg element effectively improves the wear resistance of the alloy under the large load.

Comparing the wear loss of the two Al-Sn bearing alloys in the image 5 under a small load, the example alloy containing Mg has smaller wear loss under different loads, and compared with the comparative alloy, the wear quality of the example alloy is respectively reduced by about 27%, 28% and 32% under 2N, 5N and 8N, which shows that the example alloy has better wear resistance, and the addition of a proper amount of Mg element effectively improves the wear resistance of the alloy under a small load.

Table 1 shows the hardness of the two homogenized alloys, and by comparison, it can be seen that the hardness of the alloy of the example is increased by about 12% compared to the alloy of the comparative example, indicating that the addition of a suitable amount of Mg element effectively increases the hardness of the alloy.

TABLE 1 comparison of mechanical properties of two homogenized alloys

Test specimen	hardness/HV
		Examples	47±1
Comparative example	42±2

In conclusion, under the same smelting preparation process and homogenization process, the Al-12Sn-4Si-1.5Mg (wt.%) alloy has better wear resistance than the Al-12Sn-4Si (wt.%), and the addition of a small amount of Mg in the Al-Sn alloy is helpful for refining the alloy structure and improving the alloy hardness and wear resistance.

The invention has been described above with reference to the accompanying drawings, and it is obvious that the invention is not limited to the specific implementation in the above-described manner, and it is within the scope of the invention to adopt various insubstantial modifications of the inventive method concept and solution, or to apply the inventive concept and solution directly to other applications without such modifications.

Claims

1. The wear-resistant Mg-containing aluminum-tin bearing bush alloy is characterized in that: the alloy ingot is prepared from (by weight) Sn 8-12%, Si 2.5-4%, Mg 0.5-1.5%, Sn/Si 3-4%, and Al and inevitable impurity elements in balance by maintaining the temperature of the alloy ingot at 470-490 ℃ for 3.5-4.5 hours.

2. A method of making a wear resistant Mg-containing aluminum tin bearing shell alloy of claim 1, comprising the steps of: the preparation method comprises the following steps of proportioning, smelting, slagging off, stirring according to designed alloy components, pouring at a temperature range of 760-820 ℃, cooling to room temperature by water to obtain an ingot, and preserving heat of the ingot for 3.5-4.5 hours at a temperature range of 470-490 ℃.