CN101323900A - High speed processing method for realizing superfine crystal grain structure on metallic material surface - Google Patents

Abstract

The invention relates to a processing method for high-speed deformation of the surface of a metal material with a nanostructure, and in particular provides a high-speed processing method for realizing an ultrafine grain structure on the surface of the metal material. At room temperature or low temperature, through the mechanical treatment method of high-speed plastic deformation, the micron-scale coarse grain structure on the surface of the metal material is refined into nearly equiaxed submicron grains or nano-grains, and ultra-fine grains are formed on the surface of the metal material granular structure. With the increase of the depth from the treated surface, the size of the microstructure changes in a gradient, from nanometer and submicron to micron. Compared with the existing processing method for forming superfine grain structure on the surface, the high-speed processing method of the present invention obviously reduces the surface roughness of the processed metal material, increases the thickness of the deformed layer, and has simple processing method and high working efficiency.

Description

A high-speed machining method for realizing ultra-fine grain structure on the surface of metal materials

technical field

The invention relates to a treatment method for high-speed deformation of the surface of a metal material with a nanostructure, and in particular provides a high-speed processing method for realizing an ultra-fine grain structure on the surface of a metal material, forming nano-sized and sub-micron-sized ultra-fine particles on the surface of the metal material. Grain structure.

Background technique

Nanomaterials are single-phase or multi-phase crystalline materials composed of substructures with a structural size less than 100nm. Since the grain boundaries of nanomaterials occupy a large proportion, nanomaterials usually have excellent properties that are different from and often superior to ordinary polycrystalline materials. , such as high strength, high diffusion coefficient, good electrical and magnetic properties.

At present, research in the field of nanostructured materials mainly focuses on the synthesis, preparation, structural characteristics, and thermal stability of bulk nanostructured materials. From the existing methods, methods such as gas phase condensation and mechanical ball milling are difficult to eliminate the adverse effects of defects such as holes and pollution in the prepared materials; The plastic deformation method makes up for the shortcomings of the above-mentioned methods, but the equipment loss is large, the work efficiency is low, and the cost is high; the shape and size of the processed materials have great limitations, and it is difficult to realize industrial application.

In fact, the failure of materials mostly occurs on the surface of the material, so the quality of the surface structure of the material directly affects the comprehensive performance indicators of engineering metal materials. The microstructure size of the surface layer of conventional engineering materials is refined to the nanometer and submicron scale, and the excellent performance of nanostructure materials is used to improve the structure and performance of the material surface, especially the fatigue performance, corrosion performance, friction and wear performance, etc., thereby improving Comprehensive performance and service behavior of engineering materials.

The existing metal material surface treatment methods mainly include: (1) surface coating. Using coating and deposition techniques such as PVD, CVD, sputter coating, electroplating and other methods to generate a nanostructure layer on the surface of the base material. The key to this technology is the bonding force between the coating and the substrate and between the coating particles. The easiest and most frequent failure is the peeling or falling off of the coating. In addition, the investment in equipment is large and the production cost is high, so it is not suitable for the surface treatment of a large number of engineering metal materials; (2) surface mechanical treatment. Using the surface mechanical grinding treatment technology, under the repeated action of external load, the coarse-grained structure on the surface of the material undergoes strong plastic deformation in different directions and gradually fragments to the nanometer level. However, the surface roughness of the sample obtained by this processing technology is relatively large at present, which cannot meet the requirements of practical applications, which limits its promotion in industry, and the shape of the processed sample also has great limitations. In addition, the operating procedures are relatively cumbersome, and the consumption of trays and pellets used for grinding is large, resulting in increased costs.

Contents of the invention

The purpose of the present invention is to provide a new type of metal material surface high-speed deformation treatment method, which has low investment, simple operation, and easy industrial realization. The nano and submicron structure layers prepared by it are not easy to fall off, and can be controlled by various conditions. It handles workpieces with complex shapes while ensuring low surface roughness, and can also use relatively mature machining cooling technology, thus providing the possibility to comprehensively improve the surface properties of engineering metal materials.

Technical scheme of the present invention is:

The invention provides a high-speed deformation treatment method for the surface of metal materials. The treatment method device is composed of a workpiece high-speed movement mechanism, a tool feed mechanism and a cooling mechanism. The invention adopts a tool with a certain radius of curvature to perform axial feed movement, and the workpiece to be processed performs high-speed rotational movement, and selects different cooling media for cooling to control the surface temperature of the metal material during processing. Among them, the preferred range of the radius of curvature of the tool is 4mm---8mm; the preferred range of the axial feed speed of the tool is 150mm/min---250mm/min; the preferred range of the workpiece speed to be processed is 600rpm---1000rpm; The surface temperature of the metal material of the workpiece preferably ranges from -100°C to 20°C; the cooling medium can be high-pressure oil mist or liquid nitrogen gas.

The principle of the present invention is to cause serious plastic deformation on the surface of metal materials through high-speed deformation, so that the surface grains are refined to nanometer size through processes such as dislocation proliferation, movement, annihilation, and rearrangement. Therefore any equipment that can cause the tool and the workpiece to exhibit high-speed relative motion can be used as the structure of the present invention, such as various lathes, grinding machines and the like.

Using high-speed deformation technology, low-temperature multiple deformation treatment is performed on the surface of the workpiece. Process parameters:

Deformation strain rate: 10 ³ -10 ⁶ s ^-1 ;

Deformation strain: the total deformation is greater than 2.9 (calculation method: $\mathrm{\ϵ}=\mathrm{\γ}/\sqrt{3},$ ε is the amount of deformation, γ is the shear strain);

Deformation temperature: -196°C---100°C.

The present invention has the following advantages:

1. The processing method is simple. The invention utilizes high-speed deformation technology, has a simple processing method, and is easy to control deformation process parameters and deformation temperature. Necessary improvements are made to the current traditional cutting technology, and the process parameters and deformation temperature are optimized to obtain a refined surface structure layer.

2. Strong applicability. It is suitable for the surface treatment of various complex workpieces, and only adjusts the microstructure of the material to strengthen metals and alloys without changing the chemical composition of the material.

3. High surface quality after treatment. The treatment method of the method ensures the uniformity of the entire surface treatment, thereby obtaining a lower surface roughness, increasing the thickness of the deformed layer, and after the treatment is completed, it is easy to repair the surface by various conventional industrial means.

In the present invention, through high-speed deformation treatment on the surface of the metal material, a nanometer and submicron tissue structure with a certain thickness is formed on the surface of the material, while the surface layer and the overall composition of the material remain unchanged. Grain size distribution: Along the depth direction, within a certain thickness of the surface layer (thickness is about 20μm---300μm), there are nanometer and submicron-sized refined structures, deformed structure layers and coarse grain structures of the matrix. Since the damage of the material originates from the surface of the material, the optimization of the surface structure is beneficial to the improvement of the basic properties of the material. For example, fine grains are better than coarse grains in inhibiting crack growth. Conversely, coarser grains are better than finer grains in resisting crack propagation. In this way, the ideal combination of the fine grain surface layer and the coarse grain matrix is more beneficial to prolong the service life of the material. In a word, the present invention combines the excellent properties of nanomaterials with engineering metal materials, endowing traditional metal materials with special properties, which has very broad prospects in both basic research and engineering applications.

Description of drawings

Fig. 1 is the transmission electron microscope photo (spindle speed: 600rpm) of the surface layer of pure copper material processed by the technology of the present invention.

Fig. 2 is a transmission electron microscope photograph of the surface layer of the pure copper material processed by the technology of the present invention (spindle speed: 1000rpm).

Figure 3(a)-(c) is the surface TEM bright (a), dark (b) field image and diffraction (c) photo of the pure copper material processed by the technology of the present invention (spindle speed: 600rpm).

Fig. 4 is a schematic structural diagram of the device used in the treatment method of the present invention. In the figure, 1 workpiece clamping and rotating mechanism; 2 tool clamping and feeding mechanism; 3 oil mist cooling nozzle; 4 cooling medium; 5 workpiece; 6 tool.

Detailed ways

As shown in Figure 4, the device used in the processing method of the present invention is composed of a workpiece clamping and rotating mechanism 1, a tool clamping and feeding mechanism 2, an oil mist cooling nozzle 3, a cooling medium 4, a workpiece 5, and a tool 6. The process is as follows: the present invention uses a tool 6 with a certain radius of curvature to perform axial feed motion driven by the tool clamping and feeding mechanism 2, and the processed workpiece 5 is driven by the workpiece clamping and rotating mechanism 1 to perform high-speed rotation Movement, choose different cooling media for cooling to control the temperature of the metal material surface during processing, the high-pressure oil mist sprayed from the cooling nozzle 3 (the air supply pressure of the fuel injector is greater than 80psi), and liquid nitrogen cooling gas as the cooling medium 4. Among them, the preferred range of the radius of curvature of the tool is 4mm---8mm; the preferred range of the axial feed speed of the tool is 150mm/min---250mm/min; the preferred range of the workpiece speed to be processed is 600rpm---1000rpm; The surface temperature of the metal material of the workpiece preferably ranges from -100°C to 20°C.

The present invention is described in detail below by way of examples.

Example 1

Treatment of pure copper materials using surface high-speed deformation technology:

Equipment: Surface high-speed deformation treatment equipment;

Spindle speed: 600rpm;

Deformation strain rate: 10 ³ -10 ⁴ s ^-1 ;

Deformation strain: 3-5;

Deformation temperature: 20°C;

Processing passes: 8;

Pure copper material: purity 99.97% (weight percent), annealed at 600° C. for 3 hours, grain size 20 μm.

The pure copper material with a refined surface layer is obtained after treatment, as shown in Figure 1, the surface layer thickness is about 60 μm, and the main characteristics of its microstructure are submicron grains/subgrains that are close to equiaxes, the short axis size is 164nm, and the long axis size is 351nm .

Example 2

Treatment of pure copper materials using surface high-speed deformation technology:

Equipment: Surface high-speed deformation treatment equipment;

Spindle speed: 1000rpm;

Deformation strain rate: 10 ³ -10 ⁴ s ^-1 ;

Deformation strain: 3-5;

Deformation temperature: 20°C;

Processing passes: 8;

Pure copper material: purity 99.97%, annealed at 600°C for 3 hours, grain size 20μm.

The surface structure obtained after the treatment is shown in Figure 2, the surface thickness is about 30 μm, the short axis size is 178 nm, and the long axis size is 587 nm.

Example 3

Treatment of pure copper materials using surface high-speed deformation technology:

Equipment: Surface high-speed deformation processing equipment;

Spindle speed: 600rpm;

Deformation strain rate: 10 ³ -10 ⁴ s ^-1 ;

Deformation strain: 3-5;

Deformation temperature: 20°C;

Processing passes: 6;

Pure copper material: purity 99.97%, annealed at 600°C for 3 hours, grain size 20μm.

The thickness of the treated surface layer is about 30 μm, the short axis dimension is 158nm, and the long axis dimension is 604nm.

Example 4

Treatment of pure copper materials using surface high-speed deformation technology:

Equipment: Surface high-speed deformation treatment equipment;

Spindle speed: 600rpm;

Deformation strain rate: 10 ³ -10 ⁴ s ^-1 ;

Deformation strain: 3-5;

Deformation temperature: -100°C;

Processing passes: 6;

Pure copper material: purity 99.97%, annealed at 600°C for 3 hours, grain size 20μm.

The treated surface layer is nearly equiaxed nanocrystals, the minor axis size of the crystal grains within 5 μm of the outermost layer is 19 nm, the major axis size is 38 nm, and the thickness of the nanolayer is about 20 μm, as shown in Figure 3(a)-(c), The surface transmission electron microscope bright and dark field images and diffraction photos of the pure copper material processed by the technology of the present invention.

Comparative example 1

The lamellar spacing of pure copper after 8 passes of equal channel extrusion (ECAP) is 290 ± 160nm. The fundamental difference between the method of the present invention and this method is that the method adopts a low temperature high strain rate deformation technology, which can make the pure copper surface crystal The particle size is reduced to nanometer size.

Comparative example 2

The average grain/dislocation cell size of the surface layer was 160nm after the surface mechanical grinding treatment of pure copper for 5 minutes. Compared with the surface mechanical grinding treatment method, the method of the present invention has the advantages that the microstructure is more uniform along the surface direction and the surface roughness is obviously reduced.

Claims (8)

1. high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer is characterized in that: utilize the high speed relative movement on cutter and processed workpiece surface, workpiece surface is carried out repeatedly deformation process of low temperature, processing parameter:

Deformation strain speed: 10 ³---10 ⁶s ^-1

The deformation strain amount: total deformation is greater than 2.9, method of calculation: $\mathrm{\ϵ}=\mathrm{\γ}/\sqrt{3},$ ε is a deflection, and γ is tangential strain;

Texturing temperature :-196 ℃ to 100 ℃.

2. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 1, it is characterized in that: deformation strain amount preferable range is 3-5.

3. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 1, it is characterized in that: cutter is done axial feed motion, processed workpiece rotates, and adopts heat-eliminating medium to cool off the temperature of controlling metal material surface when handling.

4. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 3, it is characterized in that: the radius-of-curvature preferable range of cutter is 4mm---8mm.

5. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 3, it is characterized in that: the axial feed velocity preferable range of cutter is 150mm/min---250mm/min.

6. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 3, it is characterized in that: processed workpiece rotating speed preferable range is 600rpm---1000rpm.

7. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 3, it is characterized in that: the metal material surface temperature preferable range of processed workpiece is-100 ℃---20 ℃.

8. according to the described high-speed processing method of realizing superfine crystal grain structure on the metallic substance top layer of claim 3, it is characterized in that: heat-eliminating medium is high pressure mist of oil, liquid nitrogen gas.

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