CN110670103A - Micro-arc oxidation treatment method for surface of aluminum alloy die - Google Patents

Abstract

The invention discloses a micro-arc oxidation treatment method for the surface of an aluminum alloy die, which relates to the technical field of aluminum alloy treatment and comprises the following steps of (1) preparing an activating solution; (2) cleaning an aluminum alloy mold, (3) preparing a composite electrolyte, (4) carrying out micro-arc oxidation treatment; the method of the invention carries out micro-arc oxidation treatment on the surface of the aluminum alloy die, and can form a layer of compact and smooth oxide film on the surface of the aluminum alloy die.

Description

Micro-arc oxidation treatment method for surface of aluminum alloy die

Technical Field

The invention belongs to the technical field of aluminum alloy treatment, and particularly relates to a micro-arc oxidation treatment method for the surface of an aluminum alloy die.

Background

With the rapid development of society, the production scale of modern industry is continuously enlarged, the demand of the die is more and more, and the quality requirement is higher and higher. The aluminum alloy die is repeatedly contacted with the alloy in a high-temperature state in the service process, and the structural properties of the die material, particularly the surface layer, are gradually evolved under the action of periodic alternating thermal stress, so that the die material is finally failed. The hot melt loss is an important cause of aluminum alloy molds. In order to improve the service performance of the die and prolong the service life of the die, a surface treatment technology is introduced. The surface treatment technology is mainly used for improving the capability of the material for resisting the environmental action by applying various coatings or changing the surface appearance, chemical composition, phase composition, microstructure, defect state or stress state of the material by adopting mechanical, physical, chemical and other methods.

However, the existing surface treatment technology has limited improvement on the surface performance of the aluminum alloy die, especially the high temperature resistance, and simultaneously, stress change can occur to influence the performance of the aluminum alloy die.

Disclosure of Invention

The invention aims to provide a micro-arc oxidation treatment method for the surface of an aluminum alloy die aiming at the existing problems.

The invention is realized by the following technical scheme:

a micro-arc oxidation treatment method for the surface of an aluminum alloy die comprises the following steps:

(1) dissolving lanthanum acetate in deionized water to prepare a lanthanum acetate solution with the mass fraction of 0.02-0.03%, then dropwise adding a sodium hypophosphite solution into the lanthanum acetate solution, stirring at the rotating speed of 120r/min while dropwise adding, and continuously stirring for 20-25min after dropwise adding is finished;

(2) cleaning an aluminum alloy mold, namely soaking and cleaning the aluminum alloy mold by using acetone, carrying out ultrasonic treatment for 5min, filtering, drying to constant weight, then putting the aluminum alloy mold into an activation solution, soaking for 1 hour at the temperature of 80 ℃ in water bath, filtering, washing to neutrality, and drying to constant weight;

(3) preparing a composite electrolyte, namely adding sodium silicate and sodium hydroxide into deionized water, uniformly stirring at the rotating speed of 500r/min to obtain a basic electrolyte, then adding cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder and a dispersing agent into the basic electrolyte, and uniformly stirring to obtain the composite electrolyte;

(4) and micro-arc oxidation treatment, namely connecting the aluminum alloy mold to the anode of the electrolytic cell, connecting the stainless steel plate to the cathode of the electrolytic cell, wherein the distance between the aluminum alloy mold and the stainless steel plate is 150-160mm, the power supply pulse number is 450, the pulse width is 75 microseconds, the power supply voltage is 300 volts, the micro-arc oxidation treatment is 13-15 minutes, the temperature is 28-30 ℃, and then taking out, cleaning by using deionized water, and drying to constant weight to obtain the aluminum alloy material.

As a further technical scheme, the mass of the sodium hypophosphite solution is 10% of that of the lanthanum acetate solution, and the concentration of the sodium hypophosphite solution is 0.5%.

As a further technical scheme, the ultrasonic treatment frequency is 30kHz, and the power is 500W.

As a further technical scheme, the concentration of sodium silicate in the basic electrolyte is 12g/L, and the concentration of sodium hydroxide is 1.4 g/L.

As a further technical scheme, the addition amount of the cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder is 1.2-1.5% of the mass of the basic electrolyte.

As a further technical scheme, the preparation method of the lanthanum chloride-polyhydroxyaluminum composite modified nano zeolite powder comprises the following steps:

(1) uniformly dispersing nano zeolite powder into deionized water to prepare nano zeolite powder dispersion liquid with the mass fraction of 10%, then adding ethanol with the mass percent of 20% into the nano zeolite powder dispersion liquid, uniformly stirring, then adding an organosilane coupling agent with the mass percent of 0.8% of the nano zeolite powder dispersion liquid, continuously stirring for 1 hour under the heating of a water bath at the temperature of 80 ℃, then filtering, washing and drying to constant weight;

(2) uniformly stirring and mixing an aluminum chloride solution and a sodium hydroxide solution at a volume ratio of 1:1 at 38 ℃ at a rotating speed of 800r/min in an equal volume, then dropwise adding a lanthanum chloride solution with the volume of 25% that of the aluminum chloride solution, continuously stirring for 35min, and then standing and aging for 2 hours to obtain a lanthanum chloride-polyhydroxyaluminum composite modification solution; the concentration of the aluminum chloride solution is 0.1mol/L, the concentration of the sodium hydroxide solution is 0.1mol/L, and the mass fraction of the lanthanum chloride solution is 0.02%;

(3) and (2) mixing the nano zeolite powder treated in the step (1) with a solvent of 180-: adding 250mL of the lanthanum chloride-polyhydroxyaluminum composite modifying solution prepared in the step (2) in proportion, stirring for 1 hour at the rotation speed of 1000r/min under the water bath heat preservation of 70 ℃, then carrying out microwave treatment for 150s, then filtering, washing to be neutral, and drying to be constant weight to obtain the lanthanum chloride-polyhydroxyaluminum composite modifying solution.

According to a further technical scheme, the dispersing agent is sodium hexametaphosphate, and the adding amount of the dispersing agent is 3.5% of the mass of the basic electrolyte.

Has the advantages that: the method can reduce the generation of micro cracks and improve the quality and the service life of the oxide film, can lead the thickness of a loose layer to be continuously increased along with the increase of the thickness of the oxide film in the micro-arc oxidation treatment process, can lead the internal stress of the film layer to be generated due to the difference of expansion coefficients between the loose layer and a compact layer, and can lead micro defects in pores to become crack sources The method has the advantages that the method is uniform, so that the method can be uniform and compounded with an oxide film layer, the generation of crack sources can be reduced, the oxide film is more compact, the high-temperature resistance of the formed composite oxide film is greatly improved, excellent heat and shock resistance is realized, and the service life and application range of the aluminum alloy die are greatly expanded.

Detailed Description

Example 1

A micro-arc oxidation treatment method for the surface of an aluminum alloy die comprises the following steps:

(1) dissolving lanthanum acetate in deionized water to prepare a lanthanum acetate solution with the mass fraction of 0.02%, then dropwise adding a sodium hypophosphite solution into the lanthanum acetate solution, stirring at the rotating speed of 120r/min while dropwise adding, and continuously stirring for 20min after dropwise adding is finished;

(2) cleaning an aluminum alloy mold, namely soaking and cleaning the aluminum alloy mold by using acetone, carrying out ultrasonic treatment for 5min, filtering, drying to constant weight, then putting the aluminum alloy mold into an activation solution, soaking for 1 hour at the temperature of 80 ℃ in water bath, filtering, washing to neutrality, and drying to constant weight;

(3) preparing a composite electrolyte, namely adding sodium silicate and sodium hydroxide into deionized water, uniformly stirring at the rotating speed of 500r/min to obtain a basic electrolyte, then adding cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder and a dispersing agent into the basic electrolyte, and uniformly stirring to obtain the composite electrolyte;

(4) and micro-arc oxidation treatment, namely connecting the aluminum alloy mold to the anode of the electrolytic cell, connecting the stainless steel plate to the cathode of the electrolytic cell, wherein the distance between the aluminum alloy mold and the stainless steel plate is 150mm, the power supply pulse number is 450, the pulse width is 75 microseconds, the power supply voltage is 300V, the micro-arc oxidation treatment is 13min, the temperature is 28 ℃, then taking out, cleaning by using deionized water, and drying to constant weight to obtain the aluminum alloy stainless steel plate.

As a further technical scheme, the mass of the sodium hypophosphite solution is 10% of that of the lanthanum acetate solution, and the concentration of the sodium hypophosphite solution is 0.5%.

As a further technical scheme, the ultrasonic treatment frequency is 30kHz, and the power is 500W.

As a further technical scheme, the concentration of sodium silicate in the basic electrolyte is 12g/L, and the concentration of sodium hydroxide is 1.4 g/L.

As a further technical scheme, the addition amount of the cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder is 1.2% of the mass of the basic electrolyte.

As a further technical scheme, the preparation method of the lanthanum chloride-polyhydroxyaluminum composite modified nano zeolite powder comprises the following steps:

(1) uniformly dispersing nano zeolite powder into deionized water to prepare nano zeolite powder dispersion liquid with the mass fraction of 10%, then adding ethanol with the mass percent of 20% into the nano zeolite powder dispersion liquid, uniformly stirring, then adding an organosilane coupling agent with the mass percent of 0.8% of the nano zeolite powder dispersion liquid, continuously stirring for 1 hour under the heating of a water bath at the temperature of 80 ℃, then filtering, washing and drying to constant weight;

(2) uniformly stirring and mixing an aluminum chloride solution and a sodium hydroxide solution at a volume ratio of 1:1 at 38 ℃ at a rotating speed of 800r/min in an equal volume, then dropwise adding a lanthanum chloride solution with the volume of 25% that of the aluminum chloride solution, continuously stirring for 35min, and then standing and aging for 2 hours to obtain a lanthanum chloride-polyhydroxyaluminum composite modification solution; the concentration of the aluminum chloride solution is 0.1mol/L, the concentration of the sodium hydroxide solution is 0.1mol/L, and the mass fraction of the lanthanum chloride solution is 0.02%;

(3) mixing the nano zeolite powder treated in the step (1) according to the weight ratio of 180 g: adding 250mL of the lanthanum chloride-polyhydroxyaluminum composite modifying solution prepared in the step (2) in proportion, stirring for 1 hour at the rotation speed of 1000r/min under the water bath heat preservation of 70 ℃, then carrying out microwave treatment for 150s, then filtering, washing to be neutral, and drying to be constant weight to obtain the lanthanum chloride-polyhydroxyaluminum composite modifying solution.

According to a further technical scheme, the dispersing agent is sodium hexametaphosphate, and the adding amount of the dispersing agent is 3.5% of the mass of the basic electrolyte.

Example 2

A micro-arc oxidation treatment method for the surface of an aluminum alloy die comprises the following steps:

(1) dissolving lanthanum acetate in deionized water to prepare a lanthanum acetate solution with the mass fraction of 0.03%, then dropwise adding a sodium hypophosphite solution into the lanthanum acetate solution, stirring at the rotating speed of 120r/min while dropwise adding, and continuously stirring for 25min after dropwise adding is finished;

(2) cleaning an aluminum alloy mold, namely soaking and cleaning the aluminum alloy mold by using acetone, carrying out ultrasonic treatment for 5min, filtering, drying to constant weight, then putting the aluminum alloy mold into an activation solution, soaking for 1 hour at the temperature of 80 ℃ in water bath, filtering, washing to neutrality, and drying to constant weight;

(3) preparing a composite electrolyte, namely adding sodium silicate and sodium hydroxide into deionized water, uniformly stirring at the rotating speed of 500r/min to obtain a basic electrolyte, then adding cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder and a dispersing agent into the basic electrolyte, and uniformly stirring to obtain the composite electrolyte;

(4) and micro-arc oxidation treatment, namely connecting the aluminum alloy mold to the anode of the electrolytic cell, connecting the stainless steel plate to the cathode of the electrolytic cell, wherein the distance between the aluminum alloy mold and the stainless steel plate is 160mm, the power supply pulse number is 450, the pulse width is 75 microseconds, the power supply voltage is 300V, the micro-arc oxidation treatment is 15min, the temperature is 30 ℃, then taking out, cleaning by using deionized water, and drying to constant weight to obtain the aluminum alloy stainless steel plate.

As a further technical scheme, the mass of the sodium hypophosphite solution is 10% of that of the lanthanum acetate solution, and the concentration of the sodium hypophosphite solution is 0.5%.

As a further technical scheme, the ultrasonic treatment frequency is 30kHz, and the power is 500W.

As a further technical scheme, the concentration of sodium silicate in the basic electrolyte is 12g/L, and the concentration of sodium hydroxide is 1.4 g/L.

As a further technical scheme, the addition amount of the cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder is 1.5% of the mass of the basic electrolyte.

As a further technical scheme, the preparation method of the lanthanum chloride-polyhydroxyaluminum composite modified nano zeolite powder comprises the following steps:

(1) uniformly dispersing nano zeolite powder into deionized water to prepare nano zeolite powder dispersion liquid with the mass fraction of 10%, then adding ethanol with the mass percent of 20% into the nano zeolite powder dispersion liquid, uniformly stirring, then adding an organosilane coupling agent with the mass percent of 0.8% of the nano zeolite powder dispersion liquid, continuously stirring for 1 hour under the heating of a water bath at the temperature of 80 ℃, then filtering, washing and drying to constant weight;

(2) uniformly stirring and mixing an aluminum chloride solution and a sodium hydroxide solution at a volume ratio of 1:1 at 38 ℃ at a rotating speed of 800r/min in an equal volume, then dropwise adding a lanthanum chloride solution with the volume of 25% that of the aluminum chloride solution, continuously stirring for 35min, and then standing and aging for 2 hours to obtain a lanthanum chloride-polyhydroxyaluminum composite modification solution; the concentration of the aluminum chloride solution is 0.1mol/L, the concentration of the sodium hydroxide solution is 0.1mol/L, and the mass fraction of the lanthanum chloride solution is 0.02%;

(3) mixing the nano zeolite powder treated in the step (1) according to the weight ratio of 200 g: adding 250mL of the lanthanum chloride-polyhydroxyaluminum composite modifying solution prepared in the step (2) in proportion, stirring for 1 hour at the rotation speed of 1000r/min under the water bath heat preservation of 70 ℃, then carrying out microwave treatment for 150s, then filtering, washing to be neutral, and drying to be constant weight to obtain the lanthanum chloride-polyhydroxyaluminum composite modifying solution.

According to a further technical scheme, the dispersing agent is sodium hexametaphosphate, and the adding amount of the dispersing agent is 3.5% of the mass of the basic electrolyte.

Example 3

A micro-arc oxidation treatment method for the surface of an aluminum alloy die comprises the following steps:

(1) dissolving lanthanum acetate in deionized water to prepare a lanthanum acetate solution with the mass fraction of 0.026%, dropwise adding a sodium hypophosphite solution into the lanthanum acetate solution, stirring at the rotating speed of 120r/min while dropwise adding, and continuously stirring for 22min after dropwise adding is finished;

(2) cleaning an aluminum alloy mold, namely soaking and cleaning the aluminum alloy mold by using acetone, carrying out ultrasonic treatment for 5min, filtering, drying to constant weight, then putting the aluminum alloy mold into an activation solution, soaking for 1 hour at the temperature of 80 ℃ in water bath, filtering, washing to neutrality, and drying to constant weight;

(3) preparing a composite electrolyte, namely adding sodium silicate and sodium hydroxide into deionized water, uniformly stirring at the rotating speed of 500r/min to obtain a basic electrolyte, then adding cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder and a dispersing agent into the basic electrolyte, and uniformly stirring to obtain the composite electrolyte;

(4) and micro-arc oxidation treatment, namely connecting the aluminum alloy mold to the anode of the electrolytic cell, connecting the stainless steel plate to the cathode of the electrolytic cell, wherein the distance between the aluminum alloy mold and the stainless steel plate is 155mm, the power supply pulse number is 450, the pulse width is 75 microseconds, the power supply voltage is 300V, the micro-arc oxidation treatment is 14min, the temperature is 29 ℃, then taking out, cleaning by using deionized water, and drying to constant weight to obtain the aluminum alloy stainless steel plate.

As a further technical scheme, the mass of the sodium hypophosphite solution is 10% of that of the lanthanum acetate solution, and the concentration of the sodium hypophosphite solution is 0.5%.

As a further technical scheme, the ultrasonic treatment frequency is 30kHz, and the power is 500W.

As a further technical scheme, the concentration of sodium silicate in the basic electrolyte is 12g/L, and the concentration of sodium hydroxide is 1.4 g/L.

As a further technical scheme, the addition amount of the cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder is 1.3% of the mass of the basic electrolyte.

As a further technical scheme, the preparation method of the lanthanum chloride-polyhydroxyaluminum composite modified nano zeolite powder comprises the following steps:

(1) uniformly dispersing nano zeolite powder into deionized water to prepare nano zeolite powder dispersion liquid with the mass fraction of 10%, then adding ethanol with the mass percent of 20% into the nano zeolite powder dispersion liquid, uniformly stirring, then adding an organosilane coupling agent with the mass percent of 0.8% of the nano zeolite powder dispersion liquid, continuously stirring for 1 hour under the heating of a water bath at the temperature of 80 ℃, then filtering, washing and drying to constant weight;

(2) uniformly stirring and mixing an aluminum chloride solution and a sodium hydroxide solution at a volume ratio of 1:1 at 38 ℃ at a rotating speed of 800r/min in an equal volume, then dropwise adding a lanthanum chloride solution with the volume of 25% that of the aluminum chloride solution, continuously stirring for 35min, and then standing and aging for 2 hours to obtain a lanthanum chloride-polyhydroxyaluminum composite modification solution; the concentration of the aluminum chloride solution is 0.1mol/L, the concentration of the sodium hydroxide solution is 0.1mol/L, and the mass fraction of the lanthanum chloride solution is 0.02%;

(3) and (2) mixing the nano zeolite powder treated in the step (1) according to a ratio of 190 g: adding 250mL of the lanthanum chloride-polyhydroxyaluminum composite modifying solution prepared in the step (2) in proportion, stirring for 1 hour at the rotation speed of 1000r/min under the water bath heat preservation of 70 ℃, then carrying out microwave treatment for 150s, then filtering, washing to be neutral, and drying to be constant weight to obtain the lanthanum chloride-polyhydroxyaluminum composite modifying solution.

According to a further technical scheme, the dispersing agent is sodium hexametaphosphate, and the adding amount of the dispersing agent is 3.5% of the mass of the basic electrolyte.

Comparative example 1

A micro-arc oxidation treatment method for the surface of an aluminum alloy die comprises the following steps:

(1) dissolving lanthanum acetate in deionized water to prepare a lanthanum acetate solution with the mass fraction of 0.02%, then dropwise adding a sodium hypophosphite solution into the lanthanum acetate solution, stirring at the rotating speed of 120r/min while dropwise adding, and continuously stirring for 20min after dropwise adding is finished;

(2) cleaning an aluminum alloy mold, namely soaking and cleaning the aluminum alloy mold by using acetone, carrying out ultrasonic treatment for 5min, filtering, drying to constant weight, then putting the aluminum alloy mold into an activation solution, soaking for 1 hour at the temperature of 80 ℃ in water bath, filtering, washing to neutrality, and drying to constant weight;

(3) preparing electrolyte, namely adding sodium silicate and sodium hydroxide into deionized water, and uniformly stirring at the rotating speed of 500r/min to obtain the electrolyte;

(4) and micro-arc oxidation treatment, namely connecting the aluminum alloy mold to the anode of the electrolytic cell, connecting the stainless steel plate to the cathode of the electrolytic cell, wherein the distance between the aluminum alloy mold and the stainless steel plate is 150mm, the power supply pulse number is 450, the pulse width is 75 microseconds, the power supply voltage is 300V, the micro-arc oxidation treatment is 13min, the temperature is 28 ℃, then taking out, cleaning by using deionized water, and drying to constant weight to obtain the aluminum alloy stainless steel plate.

As a further technical scheme, the mass of the sodium hypophosphite solution is 10% of that of the lanthanum acetate solution, and the concentration of the sodium hypophosphite solution is 0.5%.

As a further technical scheme, the ultrasonic treatment frequency is 30kHz, and the power is 500W.

As a further technical scheme, the concentration of sodium silicate in the electrolyte is 12g/L, and the concentration of sodium hydroxide is 1.4 g/L.

According to a further technical scheme, the dispersing agent is sodium hexametaphosphate, and the adding amount of the dispersing agent is 3.5% of the mass of the basic electrolyte.

Comparative example 2: the difference from the example 1 is that the lanthanum chloride-polyhydroxyaluminum composite modified nano zeolite powder is replaced by the same amount of lanthanum chloride contained in the nano zeolite powder.

Thermal shock resistance test

Heating the same aluminum alloy die subjected to surface micro-arc oxidation treatment in the embodiment and the comparative example by using a resistance furnace, preserving heat for 3min at 300 ℃, then quenching the aluminum alloy die in ice water at 0 ℃, air-drying the aluminum alloy die, heating the aluminum alloy die to 300 ℃ again, and performing thermal shock cycle, wherein the thermal shock cycle comprises 60 times and 90 times of thermal shock cycle, and observing the film layer stripping and crack generation conditions (20 samples in each group, the sample material is aluminum alloy 30 Cr):

TABLE 1

As can be seen from Table 1, the micro-arc oxidation treatment of the invention can obviously improve the thermal shock resistance of the aluminum alloy die.

The heat resistance of the aluminum alloy molds treated in the examples and the comparative examples is detected, and the temperature resistance improvement rates of the groups are compared (20 samples in each group, the average value is taken, and the sample material is aluminum alloy 30 Cr):

temperature resistance increase rate = (maximum temperature resistance after treatment-maximum temperature resistance before treatment)/maximum temperature resistance before treatment x 100%;

TABLE 2

As can be seen from Table 2, the temperature resistance of the aluminum alloy mold treated by the method is obviously improved.

Claims (7)

1. The method for micro-arc oxidation treatment of the surface of the aluminum alloy die is characterized by comprising the following steps:

(1) dissolving lanthanum acetate in deionized water to prepare a lanthanum acetate solution with the mass fraction of 0.02-0.03%, then dropwise adding a sodium hypophosphite solution into the lanthanum acetate solution, stirring at the rotating speed of 120r/min while dropwise adding, and continuously stirring for 20-25min after dropwise adding is finished;

(2) cleaning an aluminum alloy mold, namely soaking and cleaning the aluminum alloy mold by using acetone, carrying out ultrasonic treatment for 5min, filtering, drying to constant weight, then putting the aluminum alloy mold into an activation solution, soaking for 1 hour at the temperature of 80 ℃ in water bath, filtering, washing to neutrality, and drying to constant weight;

(3) preparing a composite electrolyte, namely adding sodium silicate and sodium hydroxide into deionized water, uniformly stirring at the rotating speed of 500r/min to obtain a basic electrolyte, then adding cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder and a dispersing agent into the basic electrolyte, and uniformly stirring to obtain the composite electrolyte;

(4) and micro-arc oxidation treatment, namely connecting the aluminum alloy mold to the anode of the electrolytic cell, connecting the stainless steel plate to the cathode of the electrolytic cell, wherein the distance between the aluminum alloy mold and the stainless steel plate is 150-160mm, the power supply pulse number is 450, the pulse width is 75 microseconds, the power supply voltage is 300 volts, the micro-arc oxidation treatment is 13-15 minutes, the temperature is 28-30 ℃, and then taking out, cleaning by using deionized water, and drying to constant weight to obtain the aluminum alloy material.

2. The aluminum alloy mold surface micro-arc oxidation treatment method as claimed in claim 1, wherein the mass of the sodium hypophosphite solution is 10% of that of the lanthanum acetate solution, and the concentration of the sodium hypophosphite solution is 0.5%.

3. The aluminum alloy mold surface micro-arc oxidation treatment method as claimed in claim 1, wherein the ultrasonic treatment frequency is 30kHz and the power is 500W.

4. The aluminum alloy mold surface micro-arc oxidation treatment method as claimed in claim 1, wherein the concentration of sodium silicate in the base electrolyte is 12g/L, and the concentration of sodium hydroxide is 1.4 g/L.

5. The method for the micro-arc oxidation treatment of the surface of the aluminum alloy die as claimed in claim 1, wherein the addition amount of the cerium chloride-polyhydroxyaluminum composite modified nano zeolite powder is 1.2-1.5% of the mass of the basic electrolyte.

6. The method for micro-arc oxidation treatment of the surface of the aluminum alloy die as claimed in claim 5, wherein the preparation method of the lanthanum chloride-polyhydroxyaluminum composite modified nano zeolite powder comprises the following steps:

(1) uniformly dispersing nano zeolite powder into deionized water to prepare nano zeolite powder dispersion liquid with the mass fraction of 10%, then adding ethanol with the mass percent of 20% into the nano zeolite powder dispersion liquid, uniformly stirring, then adding an organosilane coupling agent with the mass percent of 0.8% of the nano zeolite powder dispersion liquid, continuously stirring for 1 hour under the heating of a water bath at the temperature of 80 ℃, then filtering, washing and drying to constant weight;

(2) uniformly stirring and mixing an aluminum chloride solution and a sodium hydroxide solution at a volume ratio of 1:1 at 38 ℃ at a rotating speed of 800r/min in an equal volume, then dropwise adding a lanthanum chloride solution with the volume of 25% that of the aluminum chloride solution, continuously stirring for 35min, and then standing and aging for 2 hours to obtain a lanthanum chloride-polyhydroxyaluminum composite modification solution; the concentration of the aluminum chloride solution is 0.1mol/L, the concentration of the sodium hydroxide solution is 0.1mol/L, and the mass fraction of the lanthanum chloride solution is 0.02%;

(3) and (2) mixing the nano zeolite powder treated in the step (1) with a solvent of 180-: adding 250mL of the lanthanum chloride-polyhydroxyaluminum composite modifying solution prepared in the step (2) in proportion, stirring for 1 hour at the rotation speed of 1000r/min under the water bath heat preservation of 70 ℃, then carrying out microwave treatment for 150s, then filtering, washing to be neutral, and drying to be constant weight to obtain the lanthanum chloride-polyhydroxyaluminum composite modifying solution.

7. The aluminum alloy mold surface micro-arc oxidation treatment method as claimed in claim 1, wherein the dispersant is sodium hexametaphosphate, and the addition amount of the dispersant is 3.5% of the mass of the basic electrolyte.