阅读说明：本技术 一种室温下在镁锂合金表面制备含氮改性层的方法 (Method for preparing nitrogen-containing modified layer on surface of magnesium-lithium alloy at room temperature ) 是由 孙建 朱香存 陈卓 杜晓东 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种室温下在镁锂合金表面制备含氮改性层的方法,具体方法如下：将镁锂合金表面打磨,清洗后在样品表面涂抹一层促渗剂；将预处理后的镁锂合金、钢球、钛铝混合金属粉末以及促渗剂放入球磨罐中,并在真空手套箱中向球磨罐中充入氮气,将密封好的球磨罐安装在高能球磨机上,高能球磨机进行高速振动；另外钛粉和铝粉在钢球撞击的作用下在镁锂合金表面逐渐形成纳米结构的合金涂层,而且在形成涂层的同时活性氮原子又在机械力、催化效应以及纳米效应的作用下逐步渗入到合金化涂层的内部,从而形成含氮的合金化涂层。该方法是在室温下进行,基体不会受到负面影响,所得改性层表面硬度、耐磨性良好,且与基体有着良好的结合力而不易剥落。(The invention discloses a method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature, which comprises the following steps: polishing the surface of the magnesium-lithium alloy, and smearing a layer of penetration enhancer on the surface of a sample after cleaning; putting the pretreated magnesium-lithium alloy, steel balls, titanium-aluminum mixed metal powder and a penetration enhancer into a ball milling tank, filling nitrogen into the ball milling tank in a vacuum glove box, installing the sealed ball milling tank on a high-energy ball mill, and vibrating the high-energy ball mill at a high speed; in addition, titanium powder and aluminum powder gradually form a nanostructured alloy coating on the surface of the magnesium-lithium alloy under the action of impact of the steel ball, and active nitrogen atoms gradually permeate into the alloying coating under the action of mechanical force, catalytic effect and nano effect while the coating is formed, so that the nitrogen-containing alloying coating is formed. The method is carried out at room temperature, the matrix is not affected negatively, the surface hardness and the wear resistance of the obtained modified layer are good, and the modified layer has good binding force with the matrix and is not easy to peel off.)

1. A method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature is characterized by comprising the following steps:

(1) preparing a magnesium-lithium alloy material and performing surface pretreatment: cutting a magnesium-lithium alloy plate into square plates by linear cutting, polishing the surfaces of the square plates by using abrasive paper, cleaning the square plates in distilled water and absolute ethyl alcohol to remove surface oil stains, and then coating a layer of penetration enhancer on the clean magnesium-lithium alloy surface;

(2) preparation of high-energy ball milling treatment: placing the pretreated magnesium-lithium alloy plate into an auxiliary ball milling tank of a high-energy ball mill, adding a certain amount of steel balls into the ball milling tank, simultaneously adding mixed metal powder consisting of titanium and aluminum, adding a certain amount of penetration enhancer, completely discharging air in the ball milling tank in a vacuum glove box, filling nitrogen, and sealing the ball milling tank;

(3) high-energy ball milling treatment: the method comprises the steps of starting a switch of a high-energy ball milling experiment machine, carrying out high-energy ball milling treatment on a sample in a flowing nitrogen atmosphere, then carrying out high-speed vibration of the high-energy ball mill, and enabling the steel ball, powder, the sample, a penetration enhancer and the like to collide violently in the nitrogen atmosphere, so that a certain temperature is generated in a ball milling tank, nitrogen releases high-concentration active nitrogen atoms under the catalytic action of the penetration enhancer, in addition, under the action of impact of the steel ball, titanium powder and aluminum powder, an alloy coating with a nano structure is gradually formed on the surface of a magnesium-lithium alloy, and when the coating is formed, the active nitrogen atoms gradually penetrate into the interior of the alloy coating under the action of mechanical force, a catalytic effect and a nano effect, so that the nitrogen-containing alloy coating is formed.

2. The method for preparing the nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature according to claim 1, wherein the nitrogen-containing modified layer is prepared by the following steps: in the step (1), the size of the square plate is 20mm multiplied by 5mm, and ultrasonic vibration washing is adopted for washing for 5-10 min.

3. The method for preparing the nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature according to claim 1, wherein the nitrogen-containing modified layer is prepared by the following steps: in the step (2), the diameter of the steel balls is 2-8mm, the number of the steel balls is 20-40, the mass ratio of titanium to aluminum in the metal powder is 1-5: 0-2, the total weight of the powder is 5-10g, and the total weight of the penetration enhancer is 0.5-3 g.

4. The method for preparing the nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature according to any one of claims 1 to 3, wherein the method comprises the following steps: the penetration enhancer is one or more of rare earth perovskite oxides.

5. The method for preparing the nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature according to claim 4, wherein the nitrogen-containing modified layer is prepared by the following steps: the rare earth perovskite oxide is LaFeO₃、SmCoO₃、LaCoO₃The penetration enhancer comprises LaFeO₃、SmCoO₃、LaCoO₃Said LaFeO₃、SmCoO₃、LaCoO₃The mass ratio of the components is 3-8: 1-5.

6. The method for preparing the nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature according to claim 1, wherein the nitrogen-containing modified layer is prepared by the following steps: in the step (3), the ultrasonic vibration frequency of the vibration head is 50 Hz.

7. The method for preparing the nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature according to claim 1, wherein the nitrogen-containing modified layer is prepared by the following steps: in the step (3), the ball milling time is 1-7h, and in the processing process, nitrogen gas needs to be refilled into the ball milling tank every 1h of ball milling, and then ball milling is continued.

Technical Field

The invention relates to the field of magnesium-lithium alloy surface treatment, in particular to a method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature.

Background

The magnesium-lithium alloy is an ultra-light structural alloy material and is widely applied to the fields of aerospace, automobiles, 3C industry (communication equipment, electronics and computers), weapon industry, medical appliances and the like. However, since magnesium and lithium in the magnesium-lithium alloy are very active elements, a loose oxide film is easily formed on the surface of the magnesium-lithium alloy, so that the wear resistance and corrosion resistance of the magnesium-lithium alloy are poor, and the service range and the service life of the magnesium-lithium alloy are greatly limited. The preparation of the nitride modified layer of titanium nitride, aluminum nitride and the like on the surface of the magnesium-lithium alloy can greatly improve the surface hardness, the wear resistance, the corrosion resistance and the fatigue life. At present, the method for preparing the nitride modified layer on the surface of the magnesium-lithium alloy is mainly a magnetron sputtering method, but the modified layer prepared by the method has the disadvantages of thin thickness, expensive equipment and high cost.

Aiming at the problems, related researchers adopt a method of combining surface mechanical nano-alloying and nitriding to prepare a nitride modified layer on the surface of the magnesium-lithium alloy. The method comprises the steps of firstly introducing a titanium layer with a certain thickness on the surface of the magnesium-lithium alloy by using a mechanical nano alloying method, and then nitriding the titanium layer to obtain a titanium nitride modified layer. Although the research method effectively improves the surface property of the magnesium-lithium alloy, the higher nitriding temperature (400 ℃) still has negative effects on the matrix, such as the increase of the crystal grain size of the matrix, the deformation of workpieces and the like in the nitriding process. Therefore, at present, no process for preparing a thicker nitrogen-containing modified layer on the surface of the magnesium-lithium alloy at room temperature in one step exists.

Disclosure of Invention

The invention aims to provide a method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature, which can solve the technical problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature comprises the following steps:

(1) preparing a magnesium-lithium alloy material and performing surface pretreatment: cutting a magnesium-lithium alloy plate into square plates by linear cutting, polishing the surfaces of the square plates by using abrasive paper, cleaning the square plates in distilled water and absolute ethyl alcohol to remove surface oil stains, and then coating a layer of penetration enhancer on the clean magnesium-lithium alloy surface;

(2) preparation of high-energy ball milling treatment: placing the pretreated magnesium-lithium alloy plate into an auxiliary ball milling tank of a high-energy ball mill, adding a certain amount of steel balls into the ball milling tank, simultaneously adding mixed metal powder consisting of titanium and aluminum, adding a certain amount of penetration enhancer, completely discharging air in the ball milling tank in a vacuum glove box, filling nitrogen, and sealing the ball milling tank;

(3) high-energy ball milling treatment: the method comprises the steps of starting a switch of a high-energy ball milling experiment machine, carrying out high-energy ball milling treatment on a sample in a flowing nitrogen atmosphere, then carrying out high-speed vibration of the high-energy ball mill, and enabling the steel ball, powder, the sample, a penetration enhancer and the like to collide violently in the nitrogen atmosphere, so that a certain temperature is generated in a ball milling tank, nitrogen releases high-concentration active nitrogen atoms under the catalytic action of the penetration enhancer, in addition, under the action of impact of the steel ball, titanium powder and aluminum powder, an alloy coating with a nano structure is gradually formed on the surface of a magnesium-lithium alloy, and when the coating is formed, the active nitrogen atoms gradually penetrate into the interior of the alloy coating under the action of mechanical force, a catalytic effect and a nano effect, so that the nitrogen-containing alloy coating is formed.

Preferably, in the step (1), the size of the square plate is 20mm × 20mm × 5mm, and the ultrasonic vibration washing is adopted for washing for 5-10 min.

Preferably, in the step (2), the diameter of the steel balls is 2-8mm, the number of the steel balls is 20-40, and the mass ratio of titanium to aluminum in the metal powder is 1-5: 0 to 2g of powder, 5 to 10g of total weight and 0.5 to 3g of total weight of penetration enhancer.

Preferably, the penetration enhancer is one or more of rare earth perovskite oxides.

Preferably, the rare earth perovskite oxide is LaFeO₃、SmCoO₃、LaCoO₃The penetration enhancer comprises LaFeO₃、SmCoO₃、LaCoO₃Said LaFeO₃、SmCoO₃、LaCoO₃Has a mass ratio of 3-8:1-5:1-5。

Preferably, in the step (3), the ultrasonic vibration frequency of the vibration head is 50 Hz.

Preferably, in the step (3), the ball milling time is 1-7h, and in the processing process, nitrogen gas needs to be refilled into the ball milling tank every 1h of ball milling, and then ball milling is continued.

Compared with the prior art, the invention has the beneficial effects that:

1) according to the invention, by a high-energy nitrogen ball milling method, alloy powder and a penetration enhancer are added, and a nitrogen-containing modified layer with high surface hardness and good wear resistance is prepared on the surface of the magnesium-lithium alloy at room temperature under the nitrogen atmosphere, and the thickness of the modified layer is controllable.

2) The method is carried out at room temperature, the method does not need heating, the matrix is not influenced negatively, and the surface hardness and the wear resistance of the obtained modified layer are good. In addition, because an atom interdiffusion layer is arranged between the substrate and the modification layer, the modification layer and the substrate have good bonding force and are not easy to peel off.

3) The method has simple process and low cost, and is suitable for large-scale surface treatment of the flat-plate magnesium-lithium alloy material.

Drawings

FIG. 1 is a SEM photograph of a cross section of a material prepared in example 4 of the present invention;

FIG. 2 is an EDS spectroscopy analysis of the material prepared in example 4 of the present invention;

FIG. 3 is an XRD diffraction pattern of the material prepared in example 4 of the present invention;

FIG. 4 is a surface TEM photograph and micro-area spectrum analysis of the material prepared in example 4 of the present invention;

FIG. 5 is a graph showing the surface hardness of the material prepared in example 4 of the present invention as a function of depth.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

A method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature comprises the following steps:

(1) preparing a magnesium-lithium alloy material and performing surface pretreatment: cutting the magnesium-lithium alloy into square plates with the thickness of 20mm multiplied by 5mm by linear cutting, polishing the surfaces of the square plates by abrasive paper, then sequentially placing the square plates in distilled water and absolute ethyl alcohol for ultrasonic vibration washing for 5-10min, and drying the square plates by blowing to obtain the pretreated material. Then coating a layer of penetration enhancer on the surface of the clean magnesium-lithium alloy, wherein the main formula of the penetration enhancer is LaFeO with the mass ratio of 8:1:1₃、SmCoO₃、LaCoO₃，。

(2) Inflating a ball milling tank: placing the pretreated magnesium-lithium alloy plate into an auxiliary ball milling tank of a high-energy ball mill, adding 20 steel balls with the diameter of 6mm, simultaneously adding 4g of pure titanium powder, and adding a certain amount of penetration enhancer, wherein the main component of the penetration enhancer is LaFeO with the mass ratio of 8:1:1₃、SmCoO₃、LaCoO₃The total weight of the penetration enhancer is 2 g. And then, completely discharging the air in the ball milling tank in a vacuum glove box, filling nitrogen, sealing the ball milling tank and taking out.

(3) High-energy ball milling treatment: and (3) installing the sealed ball milling tank on a high-energy ball mill, starting a switch of the device, setting the ultrasonic vibration frequency of a vibration head to be 50Hz, and driving a steel ball to impact the surface of the pretreated magnesium-lithium alloy material by vibration for 1 h.

After treatment, the Mg-Li alloy surface layer forms an alloying layer with the thickness of about 80-110 μm, and the whole modification layer has the nitrogen element. The surface layer nitride is formed, so that the hardness of the surface of the material is greatly improved, the hardness of the outermost layer is 483.4HV and is far higher than that of a magnesium-lithium alloy material matrix, and the hardness of the surface shows a trend of slow gradient decrease.

Example 2

A method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature comprises the following steps:

(1) preparing a magnesium-lithium alloy material and performing surface pretreatment: cutting the magnesium-lithium alloy into square plates with the thickness of 20mm multiplied by 5mm by linear cutting, polishing the surfaces of the square plates by abrasive paper, then sequentially placing the square plates in distilled water and absolute ethyl alcohol for ultrasonic vibration washing for 5-10min, and drying the square plates by blowing to obtain the pretreated material. Then coating a layer of penetration enhancer on the surface of the clean magnesium-lithium alloy, wherein the penetration enhancer is LaFeO with the mass ratio of 4:1₃、SmCoO₃。

(2) Inflating a ball milling tank: placing the pretreated magnesium-lithium alloy plate into an auxiliary ball milling tank of a high-energy ball mill, adding 30 steel balls with the diameter of 4mm, simultaneously adding 3g of pure titanium powder, and adding a certain amount of penetration enhancer which mainly comprises LaFeO with the mass ratio of 4:1₃、SmCoO₃The total weight of the penetration enhancer is 1 g. And then, completely discharging the air in the ball milling tank in a vacuum glove box, filling nitrogen, sealing the ball milling tank and taking out.

(3) High-energy ball milling treatment: installing a sealed ball milling tank on a high-energy ball mill, starting a device switch, setting the ultrasonic vibration frequency of a vibration head to be 50Hz, driving a steel ball to impact the surface of the pretreated magnesium-lithium alloy material through ultrasonic vibration, wherein the processing time is 4h, and in the processing process, nitrogen needs to be refilled into the ball milling tank every 1h of ball milling, and then ball milling is continued.

After treatment, the Mg-Li alloy surface layer forms an alloying layer with the thickness of about 80-120 μm, and the whole modification layer has the nitrogen element. The formation of the surface layer nitride greatly improves the hardness of the surface of the material, the hardness of the outermost layer is 501.6HV and is far higher than that of the magnesium-lithium alloy material matrix, and the hardness of the surface shows a trend of gradual reduction.

Example 3

A method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature comprises the following steps:

(1) preparing a magnesium-lithium alloy material and performing surface pretreatment: cutting Mg-Li alloy into 20mm × 20mm × 5mm square plates by wire cutting, polishing the surface with sand paper, sequentially placing in distilled water and anhydrous ethylUltrasonically shaking and washing for 5-10min in alcohol, and blow-drying to obtain the pretreated material. Then coating a layer of penetration enhancer on the surface of the clean magnesium-lithium alloy, wherein the main formula of the penetration enhancer is LaFeO₃。

(2) Inflating a ball milling tank: placing the pretreated magnesium-lithium alloy plate into an auxiliary ball milling tank of a high-energy ball mill, adding 25 steel balls with the diameter of 4mm, and simultaneously adding 1g of mixed powder, wherein the mass ratio of titanium to aluminum is 2: 1, in addition, a certain amount of penetration enhancer is also required to be added, and the main composition of the penetration enhancer is LaFeO₃The total weight of the penetration enhancer is 3 g. And then, completely discharging the air in the ball milling tank in a vacuum glove box, filling nitrogen, sealing the ball milling tank and taking out.

(3) High-energy ball milling treatment: installing a sealed ball milling tank on a high-energy ball mill, starting a device switch, setting the ultrasonic vibration frequency of a vibration head to be 50Hz, driving a steel ball to impact the surface of the pretreated magnesium-lithium alloy material through ultrasonic vibration, wherein the processing time is 2h, and in the processing process, nitrogen needs to be refilled into the ball milling tank every 1h of ball milling, and then ball milling is continued.

After treatment, the magnesium-lithium alloy surface layer forms an alloying layer with the thickness of about 110-160 mu m, and the whole modification layer has the existence of nitrogen element. The formation of the surface nitride greatly improves the hardness of the surface of the material, the hardness of the outermost layer is 628.9HV, which is much higher than that of the magnesium-lithium alloy material matrix, and the hardness of the surface shows the trend of slow gradient decrease.

Example 4

A method for preparing a nitrogen-containing modified layer on the surface of a magnesium-lithium alloy at room temperature comprises the following steps:

(1) preparing a magnesium-lithium alloy material and performing surface pretreatment: cutting the magnesium-lithium alloy into square plates with the thickness of 20mm multiplied by 5mm by linear cutting, polishing the surfaces of the square plates by abrasive paper, then sequentially placing the square plates in distilled water and absolute ethyl alcohol for ultrasonic vibration washing for 5-10min, and drying the square plates by blowing to obtain the pretreated material. Then coating a layer of penetration enhancer on the surface of the clean magnesium-lithium alloy, wherein the main formula of the penetration enhancer is LaFeO with the mass ratio of 4:1:1₃、SmCoO₃、LaCoO₃。

(2) Ball milling tankAnd (3) inflating: placing the pretreated magnesium-lithium alloy plate into an auxiliary ball milling tank of a high-energy ball mill, adding 20 steel balls with the diameter of 4mm, and simultaneously adding 2g of mixed powder, wherein the mass ratio of titanium to aluminum is 3: 1, in addition, a certain amount of penetration enhancer is required to be added, and the main composition of the penetration enhancer is LaFeO with the mass ratio of 4:1:1₃、SmCoO₃、LaCoO₃The total weight of the penetration enhancer is 1 g. And then, completely discharging the air in the ball milling tank in a vacuum glove box, filling nitrogen, sealing the ball milling tank and taking out.

(3) High-energy ball milling treatment: installing a sealed ball milling tank on a high-energy ball mill, starting a device switch, setting the ultrasonic vibration frequency of a vibration head to be 50Hz, driving a steel ball to impact the surface of the pretreated magnesium-lithium alloy material through ultrasonic vibration, wherein the processing time is 3h, and in the processing process, nitrogen needs to be refilled into the ball milling tank every 1h of ball milling, and then ball milling is continued.

After the treatment, as shown in FIG. 1, an alloyed layer with a thickness of about 150-180 μm is formed on the surface layer of the magnesium-lithium alloy, and the EDS spectrum shown in FIG. 2 shows that the nitrogen element exists in the whole modified layer. The XRD diffractogram shown in fig. 3 indicates that the major constituent phases of the surface nitrides are TiN and AlN. The TEM shown in fig. 4 shows that the size of the nitride particles on the surface is of the order of nanometers and the local nitrogen concentration is 4.41% (mass ratio). The hardness of the surface of the material is greatly improved by the formation of nitrides, and the hardness test shown in figure 5 shows that the hardness of the outermost layer is 651.5HV and is far higher than that of the magnesium-lithium alloy material matrix, and the hardness of the surface shows a trend of gradual reduction.

The foregoing is merely exemplary and illustrative of the present invention and various modifications, additions and substitutions may be made by those skilled in the art to the specific embodiments described without departing from the scope of the present invention as defined in the accompanying claims.