A zinc-based composite material and a method for producing the same

Abstract

The present application relates to a kind of zinc-based composite material and its preparation method, belong to zinc-based alloy technical field.The zinc-based composite material of the present application includes zinc-based alloy matrix and Si particle, graphite particle dispersed in zinc-based alloy matrix;Si particle, graphite particle accounts for the mass percentage of zinc-based composite material in turn is 5~7.5%, 5~8%;Zinc-based alloy matrix is mainly by with zinc, aluminium, copper, magnesium and titanium composition.The zinc-based composite material of the present application, hard silicon particle and soft graphite particle are dispersed in zinc-based alloy matrix, utilize the low expansion characteristics of silicon and graphite and the synergistic interaction strengthening and friction-reducing wear resistance effect of silicon Si particle and graphite particle to zinc-based alloy matrix, so that zinc-based composite material has excellent low expansion dimensional stability and low friction stability, anti occlusion and anti scratch resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to a zinc-based composite material and a preparation method thereof, and belongs to the technical field of zinc-based alloys. BACKGROUND

[0002] Zinc-aluminum alloy has excellent wear resistance, mechanical properties and significant economy, and has replaced bronze to be applied to low, medium speed, medium temperature and heavy load shaft sleeve, bearing bush and other parts. However, with the development of economy, the application of large and special-shaped parts is increasing, and higher requirements are put forward for the performance of zinc-aluminum alloy products. The expansion coefficient of cast ZA27 and ZA12 zinc alloy is (26-27.9) × 10 -6 K -1 The linear expansion coefficient of warm extruded ZA27 alloy is 24.4 × 10 -6 K -1 The expansion coefficient is large, which makes the dimensional stability of zinc alloy poor, and it is necessary to reduce the expansion coefficient. In the prior art, a Chinese invention patent with application publication number CN1140766A discloses a high-temperature-resistant low-expansion zinc-based wear-resistant alloy, the composition (mass percentage) of the alloy is aluminum 22-32%, copper 1.0-4.0%, magnesium 0.1-1.5%, calcium 0.55-2.0%, zirconium 0.02-0.09%, hafnium 0.05-0.15%, ceramic particles 1.0-10%, and the rest is zinc. The added ceramic particles are corundum, silicon carbide, borax and zinc oxide, although the expansion coefficient of the alloy is less than 18 × 10 -6 K -1 , the wear resistance can be improved, but the hard ceramic phase corundum and silicon carbide in the zinc-based alloy have too high hardness, which will increase the wear of the friction pair parts in the service condition, and produce gray abrasive particles in the running-in period, pollute the lubricating oil, and reduce the service life and performance stability of the transmission mechanism. SUMMARY

[0003] The purpose of the present application is to provide a zinc-based composite material with lower expansion coefficient and good low-friction stability.

[0004] The present application also provides a preparation method of the above-mentioned zinc-based composite material.

[0005] In order to achieve the above purpose, the technical scheme adopted by the zinc-based composite material of the present application is:

[0006] A zinc-based composite material comprises a zinc-based alloy base and Si particles and graphite particles dispersed in the zinc-based alloy base; the Si particles account for 5-8% of the mass percentage of the zinc-based composite material, and the graphite particles account for 5-8% of the mass percentage of the zinc-based composite material; the zinc-based alloy base mainly comprises zinc, aluminum, copper, magnesium and titanium, and the mass ratio of zinc, aluminum, copper, magnesium and titanium in the zinc-based alloy base is 62-70:17-22:1.0-1.5:0.50-0.75:0.10-0.15.

[0007] The zinc-based composite material disperses hard Si particles and soft graphite particles in the zinc-based alloy base, utilizes the low-expansion characteristics of Si and Gp and the synergistic interaction strengthening and friction-reducing wear-resistant effect of the Si particles and the graphite particles on the zinc-based alloy base, and improves the wear resistance of the composite material by improving the hardness of the zinc-based composite material through the Si particles and improving the self-lubricating performance through the graphite, so that the zinc-based composite material has excellent low-expansion dimensional stability and low-friction stability, anti-seizure and anti-scratching properties, and improves the service life of the zinc-based composite material for manufacturing wear-resistant parts such as automobile pistons, bushings and bearing pads.

[0008] The expansion coefficient of the zinc-based composite material can reach (14-16)×10 -6 K -1 , and the tensile strength can reach more than 300 MPa.

[0009] The crystal Si has high hardness and low expansion coefficient (4.1×10 -6 K -1 ), is distributed in the zinc alloy base in the form of particles, can improve the wear resistance of the zinc alloy, and can further reduce the expansion coefficient. Further, the average particle size of the Si particles is 5-6 μm. The unique layer lattice structure of the graphite makes it an excellent solid lubricant, and the graphite has good friction-reducing performance at room temperature-550 ℃. The dispersion of the graphite particles in the zinc-based alloy base can improve the friction-reducing and wear-resistant performance of the zinc-based composite material, reduce the expansion coefficient of the zinc-based composite material, and improve the dimensional stability of the zinc-based composite material. Further, the average particle size of the graphite particles is 15-20 μm.

[0010] Further, the Si particles account for 5-7.5% of the mass percentage of the zinc-based composite material. The mass ratio of zinc, aluminum, copper, magnesium and titanium in the zinc-based alloy base is 62-69:18.37-20.38:1.0-1.5:0.5-0.7:0.12-0.14.

[0011] The technical scheme adopted by the preparation method of the zinc-based composite material is as follows:

[0012] The application discloses a preparation method of a zinc-based composite material, and belongs to the technical field of composite materials.

[0013] The zinc-based composite material prepared by the preparation method of the zinc-based composite material has uniform microstructure, and Si phase is completely precipitated in the form of fine particles from supersaturated aluminum-silicon powder body, and the Si particles and graphite particles are uniformly dispersed in the zinc-based alloy matrix, thereby synergistically enhancing the zinc-based composite material. -6 K -1 The tensile strength of the zinc-based composite material can reach more than 300 MPa, and the zinc-based composite material has good strength, good dimensional stability and self-lubricating friction and wear resistance.

[0014] Further, the mixing is to first ball mill the zinc powder into flaky shape, and then mix the zinc powder with the aluminum-based alloy powder, the graphite powder and the modifier. The ball milling of the zinc powder into flaky shape before mixing with the aluminum-based alloy powder, the graphite powder and the modifier can avoid the agglomeration of the aluminum-silicon alloy powder, the graphite powder and the modifier, and further make the structure and composition more uniform, and improve the uniformity of the distribution of the Si particles and the graphite particles in the zinc-based composite material. The time for ball milling the zinc powder into flaky shape is preferably 20-26 h. After the zinc powder is ball milled into flaky shape, the mixing with the aluminum-based alloy powder, the graphite powder and the modifier is ball milling, and the time for ball milling is preferably 30-36 h.

[0015] The modifier can change the precipitation and growth mode of the Si phase, inhibit the growth of the Si phase, control the Si phase to form particles, and refine the size of the precipitated Si particles during the sintering process. The modifier can also form the crystal core of the zinc alloy matrix and refine the matrix. The existing modifiers used in casting can be used in the application. Further, the modifier is a rare earth oxide powder, and the mass ratio of the rare earth oxide powder to the pure zinc powder is 0.2-0.3:62-70, for example, 0.2-0.3:62-69. The rare earth oxide powder is a cerium oxide powder. The cerium oxide powder has good modification and refinement effect on the Si particles, low cost and low price. The average particle size of the modifier is 5-10 um.

[0016] Further, the average particle size of the pure zinc powder is 20-30 μm. The average particle size of the aluminum-based alloy powder is 8-15 μm, for example, 8-12 μm. The average particle size of the graphite powder is 15-20 μm. The graphite powder is obtained by spheroidizing natural flake graphite. The spheroidizing of the natural flake graphite forms near-spherical particles. The expansion coefficient of the natural flake graphite is very low, only 1.0×10 -6 K -1 The interlayer expansion coefficient of the near-spherical particles formed by the spheroidizing is greatly reduced. Controlling the average particle sizes of the rare earth oxide powder, the pure zinc powder, the graphite powder and the aluminum-based alloy powder in the above ranges can better control the sizes of the silicon particles, the graphite particles and the grain size of the zinc-based alloy matrix in the microstructure of the formed zinc-based composite material, so that a fine microstructure is obtained and the use performance of the zinc-based composite material is improved.

[0017] Further, the mass ratio of the pure zinc powder, the aluminum-based alloy powder and the graphite powder is 62-69:25-30:5-8. The magnesium element and the titanium element in the aluminum-based alloy powder diffuse during the sintering process, so that the obtained zinc-based composite material is alloyed and the tensile strength is improved.

[0018] It can be understood that the pressing and sintering of the mixed powder can be hot-pressing sintering or first pressing into a blank and then sintering. Further, the pressing and sintering is first pressing the mixed powder into a blank, and then sintering the blank. The pressing is cold isostatic pressing.

[0019] In order to further improve the mechanical properties of the zinc-based composite material, the pressure of the cold isostatic pressing is 150-180 MPa, and the pressure holding time is 20-30 min. For example, the pressure of the cold isostatic pressing is 160-180 MPa, and the pressure holding time is 25-30 min. Further, the sintering temperature is 520-530 °C, for example, 525 °C. The sintering time is determined according to the size and thickness of the composite material part, for example, the sintering time is 2-3 h.

[0020] Further, the preparation method of the zinc-based composite material further comprises the following steps: after the sintering product is pressed, stress relief annealing treatment is performed. The pressure for pressing the sintering product is 300-330 MPa, and the time is 0.1-0.2 h. Pressing the sintering product can further densify the material and improve the mechanical properties of the zinc-based composite material.

[0021] The stress relief annealing heat treatment can eliminate residual stress, improve the uniformity of alloy elements, and improve the mechanical properties of the zinc-based composite material. In order to further improve the mechanical properties of the zinc-based composite material, the temperature of the stress relief annealing heat treatment is 260-300°C, and the time is 1-2h. For example, the temperature of the stress relief annealing heat treatment is 260-280°C, and the time is 1.5-2h. DETAILED DESCRIPTION

[0022] The technical solutions of the present application are further described below in combination with the specific embodiments.

[0023] Embodiment 1

[0024] The zinc-based composite material of the present embodiment comprises a zinc-based alloy matrix and Si particles and graphite particles dispersed in the zinc-based alloy matrix, the mass percentage of the Si particles and the graphite particles in the zinc-based composite material is 7.5% and 8% respectively, the average particle size of the Si particles is 6μm, and the average particle size of the graphite particles is 15μm; the zinc-based alloy matrix is composed of zinc, aluminum, copper, magnesium and titanium elements, and the mass ratio of zinc, aluminum, copper, magnesium and titanium elements in the zinc-based alloy matrix is 62:20.38:1.5:0.6:0.12. The zinc-based composite material of the present embodiment can be prepared by using the preparation method of the zinc-based composite material of embodiment 4.

[0025] Embodiment 2

[0026] The zinc-based composite material of the present embodiment comprises a zinc-based alloy matrix and Si particles and graphite particles dispersed in the zinc-based alloy matrix, the mass percentage of the Si particles and the graphite particles in the zinc-based composite material is 5% and 6% respectively, the average particle size of the Si particles is 5μm, and the average particle size of the graphite particles is 18μm; the zinc-based alloy matrix is mainly composed of zinc, aluminum, copper, magnesium and titanium elements, and the mass ratio of zinc, aluminum, copper, magnesium and titanium elements in the zinc-based alloy matrix is 69:18.37:1.0:0.5:0.13. The zinc-based composite material of the present embodiment can be prepared by using the preparation method of the zinc-based composite material of embodiment 5.

[0027] Embodiment 3

[0028] The zinc-based composite material of the present embodiment comprises a zinc-based alloy matrix and Si particles and graphite particles dispersed in the zinc-based alloy matrix, the mass percentage of the Si particles and the graphite particles in the zinc-based composite material is 6.16% and 5% respectively, the average particle size of the Si particles is 6μm, and the average particle size of the graphite particles is 20μm; the zinc-based alloy matrix is mainly composed of zinc, aluminum, copper, magnesium and titanium elements, and the mass ratio of zinc, aluminum, copper, magnesium and titanium elements in the zinc-based alloy matrix is 67:19.60:1.4:0.7:0.14. The zinc-based composite material of the present embodiment can be prepared by using the preparation method of the zinc-based composite material of embodiment 6.

[0029] Example 4

[0030] The preparation method of the zinc-based composite material of the present example comprises the following steps:

[0031] 1) Milling industrial pure zinc powder for 20h to form thin flakes, then mixing with aluminum-silicon-copper-magnesium-titanium alloy powder, graphite powder and cerium oxide powder, and then milling for 30h to obtain a mixed powder; the mass ratio of the industrial pure zinc powder, the aluminum-silicon-copper-magnesium-titanium alloy powder, the graphite powder and the cerium oxide powder is 62:30:8:0.3;

[0032] The average particle size of the industrial pure zinc powder used is 20μm; the aluminum-silicon-copper-magnesium-titanium alloy powder used is Al-25Si-5.0Cu-2.0Mg-0.4Ti alloy powder, with an average particle size of 10μm; the graphite powder used is obtained by spheroidizing natural flake graphite, with an average particle size of 15μm; and the average particle size of the cerium oxide powder is 8μm.

[0033] 2) Cold isostatic pressing the mixed powder obtained in step 1) to form a compact, with a pressure of 180MPa and a holding time of 30min, then sintering the compact at 520℃ for 2h, then pressing the sintered product at 300MPa for 0.2h, then heating to 260℃ for 1.5h for stress relief annealing, and then air cooling to room temperature after the holding time ends.

[0034] Example 5

[0035] The preparation method of the zinc-based composite material of the present example comprises the following steps:

[0036] 1) Milling industrial pure zinc powder for 20h to form thin flakes, then mixing with aluminum-silicon-copper-magnesium-titanium alloy powder, graphite powder and cerium oxide powder, and then milling for 30h to obtain a mixed powder; the mass ratio of the industrial pure zinc powder, the aluminum-silicon-copper-magnesium-titanium alloy powder, the graphite powder and the cerium oxide powder is 62:30:8:0.3;

[0037] The average particle size of the industrial pure zinc powder used is 20μm; the aluminum-silicon-copper-magnesium-titanium alloy powder used is Al-25Si-5.0Cu-2.0Mg-0.4Ti alloy powder, with an average particle size of 10μm; the graphite powder used is obtained by spheroidizing natural flake graphite, with an average particle size of 15μm; and the average particle size of the cerium oxide powder is 8μm.

[0038] 2) Cold isostatic pressing the mixed powder obtained in step 1) to form a compact, with a pressure of 180MPa and a holding time of 30min, then sintering the compact at 520℃ for 2h, then pressing the sintered product at 300MPa for 0.2h, then heating to 260℃ for 1.5h for stress relief annealing, and then air cooling to room temperature after the holding time ends.

[0039] Example 6

[0040] The preparation method of the zinc-based composite material of the present example comprises the following steps:

[0041] 1) Milling the industrial pure zinc powder for 25h to form flake, then mixing with the Al-Si-Cu-Mg-Ti alloy powder, graphite powder and cerium oxide powder, and milling for 30h to obtain the mixed powder; the mass ratio of the industrial pure zinc powder, the Al-Si-Cu-Mg-Ti alloy powder, the graphite powder and the cerium oxide powder is 67:28:5:0.3;

[0042] The average particle size of the used industrial pure zinc powder is 25μm; the used Al-Si-Cu-Mg-Ti alloy powder is Al-22Si-5Cu-2.5Mg-0.5Ti alloy powder, and the average particle size is 12μm; the used graphite powder is obtained by spheroidizing the natural flake graphite, and the average particle size is 20μm; the average particle size of the used cerium oxide powder is 8μm.

[0043] 2) Cold isostatic pressing the mixed powder obtained in step 1) to form a compact, the pressure of the cold isostatic pressing is 180MPa, and the pressure maintaining time is 25min, then sintering the compact at 520℃ for 2h, then pressing the sintered product at 330MPa for 0.1h, then heating to 260℃ for 2h for stress relief annealing, and then air cooling to room temperature, and the zinc-based composite material is obtained.

[0044] Experimental example

[0045] The expansion coefficient and the tensile strength of the zinc-based composite material prepared in Examples 4-6 are tested respectively, the expansion coefficient is tested according to GB4339-84, and the tensile strength is tested according to GB228-87, and the results are shown in Table 1.

[0046] Table 1 Expansion coefficient and tensile strength of the zinc-based composite material prepared in Examples 4-6

[0047] Expansion coefficient / K -1 ]]> Tensile strength / MPa Example 4 14.3 x 10 -6 ]] 327 Example 5 15.8 x 10 -6 ]]> 351 Example 6 15.7 x 10 -6 ]]> 346

Claims

1. A zinc-based composite material, characterized by: The zinc-based composite material comprises a zinc-based alloy matrix and Si particles and graphite particles dispersed in the zinc-based alloy matrix; the Si particles account for 5-7.5% of the mass percentage of the zinc-based composite material, and the graphite particles account for 5-8% of the mass percentage of the zinc-based composite material; the zinc-based alloy matrix mainly comprises zinc, aluminum, copper, magnesium and titanium, and the mass ratio of zinc, aluminum, copper, magnesium and titanium in the zinc-based alloy matrix is 62-70:17-22:1.0-1.5:0.50-0.75:0.10-0.15; The zinc-based composite material is prepared by a method comprising the following steps: uniformly mixing pure zinc powder, aluminum-based alloy powder, graphite powder and a modifier to obtain mixed powder; and performing compression and sintering on the mixed powder; the aluminum-based alloy powder is composed of the following components in the following mass percentages: Si 20-25%, Cu 4.0-5.0%, Mg 2.0-2.5%, Ti 0.4-0.5%, and the balance being aluminum; and the mass ratio of the pure zinc powder, the aluminum-based alloy powder and the graphite powder is 62-70:25-30:5-8.

2. The zinc-based composite of claim 1, wherein: The average particle size of the Si particles is 5-6 μm; and the average particle size of the graphite particles is 15-20 μm.

3. A method of producing a zinc-based composite material, characterized by: The method comprises the following steps: Uniformly mixing pure zinc powder, aluminum-based alloy powder, graphite powder and a modifier to obtain mixed powder; Performing compression and sintering on the mixed powder; The aluminum-based alloy powder is composed of the following components in the following mass percentages: Si 20-25%, Cu 4.0-5.0%, Mg 2.0-2.5%, Ti 0.4-0.5%, and the balance being aluminum; and the mass ratio of the pure zinc powder, the aluminum-based alloy powder and the graphite powder is 62-70:25-30:5-8.

4. The method of producing a zinc-based composite material according to claim 3, characterized by: The modifier is a rare earth oxide powder, and the mass ratio of the rare earth oxide powder to the pure zinc powder is 0.2-0.3:62-70.

5. The method of producing a zinc-based composite material according to claim 4, characterized by: The rare earth oxide powder is cerium oxide powder; and the average particle size of the rare earth oxide powder is 5-10 μm.

6. The method of producing a zinc-based composite material according to claim 4 or 5, characterized in that: The average particle size of the pure zinc powder is 20-30 μm; the average particle size of the aluminum-based alloy powder is 8-15 μm; and the average particle size of the graphite powder is 15-20 μm.

7. The method of producing a zinc-based composite material according to claim 4 or 5, characterized in that: The graphite powder is obtained by spheroidizing natural flake graphite.

8. The method of producing a zinc-based composite material according to claim 4 or 5, characterized in that: The compression and sintering are performed by first compressing the mixed powder into a blank and then sintering the blank; the compression is cold isostatic compression; and the pressure of the cold isostatic compression is 150-180 MPa, and the pressure holding time is 20-30 min.

9. The method of producing a zinc-based composite material according to claim 4 or 5, characterized in that: The sintering temperature is 520-530 °C.

10. The method of producing a zinc-based composite material according to claim 4 or 5, characterized in that: The method further comprises the following steps: Performing compression on the sintered product and then performing stress relief annealing treatment; the stress relief annealing treatment is performed at a temperature of 260-300 °C for 1-2 h.