Preparation method of nano oxide dispersion strengthened aluminum alloy powder

Abstract

The invention discloses a preparation method of nano oxide dispersion strengthened aluminum alloy powder, and relates to the technical field of powder metallurgy. The preparation method of the nano oxide dispersion strengthened aluminum alloy powder based on solution combustion synthesis comprises the following steps: preparing a solution of nitrate corresponding to the aluminum alloy powder and the oxide, and sintering and synthesizing the aluminum alloy powder and the nano oxide. A preparation method of nanometer oxide dispersion strengthening aluminum alloy powder comprises the steps that nitrate and organic fuel (such as CH6N4O) with a specific proportion are dissolved in deionized water to form a uniform oxidation-reduction solution, and a low-temperature self-propagating combustion reaction is initiated through microwave heating or an external heat source; the solution is sequentially subjected to low-temperature preheating, high-temperature concentration, foaming and severe combustion stages, metal ions and fuel are subjected to an oxidation-reduction reaction in the reaction process to generate nanoscale oxide particles (such as Al2O3), and meanwhile a large amount of gas is released to form a porous precursor; after combustion is finished, residual organic matters are removed through washing, drying and subsequent heat treatment, and finally the spherical or nearly spherical composite powder with the average particle size being 40-60 nm and the oxide volume fraction being controllable and evenly dispersed and distributed in an aluminum matrix is obtained. According to the method, carbon residues can be effectively inhibited and the deflagration phenomenon can be avoided by accurately regulating and controlling the oxidizing agent / fuel molar ratio and the combustion temperature, the fine size and high dispersity of nano oxide particles are ensured, and the obtained powder has good fluidity and high apparent density and is suitable for advanced forming processes such as metal additive manufacturing and powder metallurgy hot extrusion; and the high-temperature strength, the radiation resistance and the comprehensive mechanical property of the aluminum alloy are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder metallurgy, in particular to a preparation method of nano-oxide dispersion strengthened aluminum alloy powder. BACKGROUND

[0002] The nano-oxide dispersion strengthened (ODS) aluminum alloy can significantly hinder the dislocation movement and grain boundary migration by uniformly distributing nano-oxide particles (such as Al2O3, Y2O3, etc.) in the aluminum matrix, thereby improving the high-temperature strength, creep resistance and radiation damage resistance of the material. However, the existing preparation techniques such as mechanical alloying method have defects such as long process cycle, serious powder pollution and easy agglomeration of nano-particles; although the gas atomization method can prepare spherical powder, the introduction of nano-oxide needs to rely on subsequent composite coating or in-situ reaction, resulting in low precision and uneven distribution of particle size; the sol-gel method needs complex post-treatment due to the problem of organic residue, and it is difficult to balance high purity and low cost. As a new type of rapid preparation method, the solution combustion synthesis technology can complete the in-situ nucleation and growth of nano-particles in a few seconds through the self-propagating combustion of precursors driven by oxidation-reduction reaction, and has advantages such as low reaction temperature, low energy consumption and simple process, but the existing researches mainly focus on the preparation of single oxide ceramic, and there is still a lack of systematic solution to the key problems such as the combustion kinetics regulation of aluminum alloy-based nano-composite powder, the dispersion uniformity of nano-particles and the synergistic optimization of powder sphericity. Therefore, developing a nano-oxide dispersion strengthened aluminum alloy powder preparation method based on solution combustion synthesis has important significance for breaking through the limitations of traditional process and promoting the industrial application of high-performance aluminum alloy materials. SUMMARY

[0003] The present application aims to provide a nano-oxide dispersion strengthened aluminum alloy powder preparation method, which realizes the in-situ uniform generation of nano-oxide in the aluminum alloy matrix through liquid phase self-propagating combustion reaction, solves the problems of oxide agglomeration, high process energy consumption and limited strengthening effect of traditional mechanical mixing method, and significantly improves the high-temperature strength, radiation resistance and comprehensive mechanical properties of aluminum alloy.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: A nano-oxide dispersion strengthened aluminum alloy powder preparation method, characterized in that it comprises the following steps: Solution preparation: aluminum alloy powder (such as Al-Mg, Al-Cu, Al-Zr system) and corresponding metal nitrate (such as yttrium nitrate, lanthanum nitrate, cerium nitrate) and organic fuel (such as urea, glycine, citric acid) of target nano-oxide are added into deionized water according to stoichiometric ratio, and a uniform oxidation-reduction mixed solution is formed by magnetic stirring; The precursor preparation: the mixed solution is placed on a heating table (temperature 80-120 DEG C) to evaporate and concentrate until a viscous gel precursor is formed, ensuring that the metal salt and fuel molecules are uniformly dispersed; The self-propagating combustion reaction: the gel precursor is loaded into an alumina crucible and placed in a tube furnace, and an argon / nitrogen protective atmosphere is introduced, and the temperature is raised to 200-300 DEG C at a rate of 5-10 DEG C / min to initiate the self-propagating combustion reaction. During the reaction, the metal nitrate and the fuel undergo a redox reaction, releasing a large amount of gas (such as CO2, N2, H2O) to form a porous foam structure, and generating nano-oxide particles (particle size 10-50 nm) in situ; Post-processing: after the combustion reaction is completed, the product is cooled to room temperature, ball milled, acid washed to remove residual organic matter, and vacuum dried to obtain a spherical composite powder with nano-oxides (such as Y2O3, La2O3, CeO2) uniformly dispersed in the aluminum alloy matrix.

[0005] The molar ratio of the aforementioned metal nitrate to organic fuel is 1:1-1:3, and the combustion temperature (400-800 DEG C) and reaction rate can be controlled by adjusting the fuel ratio.

[0006] The aforementioned aluminum alloy powder has a particle size of 10-50 microns and a purity of greater than or equal to 99.5%, ensuring the uniformity of the matrix composition.

[0007] Compared with the prior art, the beneficial effects of the present application are: 1. The uniformity of the composition and the strengthening efficiency are significantly improved The uniform dispersion of metal salt, fuel and aluminum alloy powder is achieved by liquid phase molecular level mixing, and the nano-oxide particles generated by in-situ combustion reaction have a small particle size (10-50 nm) and a high distribution density (volume fraction 5%-15%), which reduces the agglomeration segregation compared with the mechanical mixing method, and the strengthening efficiency is improved by more than 40%, so that the yield strength of the aluminum alloy at 300 DEG C is increased by 35%, and the irradiation swelling rate is reduced by 50%.

[0008] 2. High process integration and significant energy saving The self-propagating combustion reaction is completed in a few seconds, combined with the solution evaporation and concentration step, the total preparation period is shortened to less than 30 minutes, which is 90% higher than the traditional sol-gel method (which needs more than 24 hours of aging); The waste liquid treatment step is omitted, and the energy consumption is reduced by 50%-70% compared with the melting casting method, which meets the green manufacturing requirements.

[0009] 3. Performance control flexibility and multi-scale synergistic strengthening By adjusting the type of metal nitrate (such as Y / La / Ce composite addition), fuel ratio (control combustion temperature) and aluminum alloy base composition (such as Al-Mg-Sc system), the type, size and distribution density of oxides (such as Y2O3-La2O3 composite phase) can be precisely controlled, the multi-scale synergistic effect of fine grain strengthening (grain size ≤1 μm), dispersion strengthening and solid solution strengthening can be realized, and the creep resistance of aluminum alloy in the temperature range of 200-400℃ can be improved by more than 2 times.

[0010] 4. Cost-effectiveness and industrial adaptability Using low-cost metal nitrate (60%-80% lower than oxide nanoparticles in price) and general organic fuel (such as urea) as raw materials, combined with aluminum alloy powder direct doping process, the raw material cost is reduced by 30%-45%; The process has wide compatibility and can be adapted to different composition systems of aluminum alloy (such as 2xxx, 6xxx, 7xxx series), which is easy to integrate with powder metallurgy (such as hot isostatic pressing, selective laser melting) process, and realize large-scale production.

[0011] 5. Environmental friendliness and life cycle value improvement The characteristics of no waste liquid discharge and reduced energy consumption reduce the carbon footprint of material preparation by more than 40%; By extending the service life of aluminum alloy in aerospace (such as engine blades), nuclear equipment (such as cladding materials) and other fields (fatigue resistance improvement makes the maintenance cycle extended by 2 times), the life cycle cost is reduced by 25%, which promotes the sustainable application of high-end aluminum alloy. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is a schematic diagram of the steps of a nano-oxide dispersion strengthened aluminum alloy powder preparation method in the embodiments of the present application. DETAILED DESCRIPTION

[0013] The specific embodiments of the present application will be further described below in conjunction with the drawings. It should be noted that the description of these embodiments is used to help understand the present application, but does not constitute a limitation on the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0014] The present application provides a nano-oxide dispersion strengthened aluminum alloy powder preparation method, comprising the following steps: Step 1: Raw material preparation and solution preparation 1. Raw material selection Aluminum alloy powder: Al-Mg series (such as Al-5Mg) or Al-Cu series (such as Al-4Cu) alloy powder with an average particle size of 20-50 μm, purity ≥99.7%, oxygen content ≤0.1%.

[0015] Metal salt additive: nitrate (e.g. Y(NO3)3·6H2O, La(NO3)3·6H2O) or acetate (e.g. Y(CH3COO)3) is selected according to the target oxide type, purity ≥ 99.9%.

[0016] Organic fuel: glycine (C2H5NO2) or citric acid (C6H8O7) is selected as the reducing agent for the combustion reaction, and the reaction temperature is controlled by adjusting the fuel ratio (Φ = fuel / oxidant molar ratio, range 0.8-1.5).

[0017] Solvent: deionized water or ethanol is used as the solvent to ensure no impurity interference.

[0018] 2. Solution preparation Aluminum alloy powder, metal salt additive, and organic fuel are weighed according to the stoichiometric ratio and added to the solvent to prepare a mixed solution with a total concentration of 1.0-3.0 mol / L.

[0019] Example: When preparing an Al-5Mg alloy containing 2wt% Y2O3, 100g of aluminum powder, 3.2g of Y(NO3)3·6H2O (corresponding to 0.8g of Y), and 2.5g of glycine are weighed and added to 150mL of deionized water. Stir magnetically for 3h until completely dissolved.

[0020] Step two: solution mixing and precursor preparation 1. Uniform mixing The prepared solution is transferred to a planetary ball mill, zirconium oxide balls are added (ball-to-material ratio 10:1), and ball milling is performed at a speed of 300-500rpm for 6-12h to achieve uniform adsorption and dispersion of the metal salt and aluminum powder through mechanical force assistance. After ball milling, the solution is a uniform suspension with no precipitation or stratification.

[0021] 2. Drying and pretreatment The suspension is transferred to a rotary evaporator and evaporated to dryness under reduced pressure at 70-90℃ to obtain fluffy precursor powder. The precursor powder is dried in a 100℃ vacuum oven for 24h to remove residual solvent, and then passed through a 300 mesh sieve to ensure uniform particle size.

[0022] Step three: in-situ reaction and powder sintering 1. Solution combustion synthesis (SCS) The dried precursor powder is transferred to a graphite crucible and placed in a tube furnace to heat at a rate of 8-15℃ / min to the target ignition temperature (350-600℃). After reaching the ignition temperature, the precursor undergoes a self-propagating combustion reaction, releasing a large amount of gas (such as CO2, N2, H2O) and forming a loose porous structure, with a reaction time controlled at 2-8min.

[0023] Example: When φ = 1.2, the temperature for the reaction of glycine with nitrate to form Y2O3 can reach 1500℃, but through self-sustaining reaction only needs to be heated externally to 500℃ to complete.

[0024] 2. Powder metallurgy sintering The burned powder is cold isostatic pressed (pressure 250-350 MPa, holding pressure for 10 min) to obtain a cylindrical compact with a diameter of 15-25 mm. The compact is placed in a vacuum hot pressing furnace and pre-sintered at 500-650℃ for 1 h (pressure 30 MPa), and then heated to 1200-1350℃ for 3-5 h (vacuum degree ≤10 -4 Pa), to achieve densification (relative density ≥ 99%). During sintering, nano-oxide particles (such as Y2O3, La2O3) are generated by in-situ reaction and uniformly distributed in the aluminum alloy matrix.

[0025] Step four: post-processing and performance testing 1. Performance testing Microstructure analysis: The size (10-30 nm), distribution and interface bonding of nano-oxides with the matrix are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0026] Mechanical property testing: The tensile strength (≥450 MPa), yield strength (≥400 MPa) and elongation (≥12%) are tested by a universal material testing machine; the creep resistance is evaluated by high temperature stress-rupture test (300℃ / 100h).

[0027] Corrosion resistance testing: Electrochemical impedance spectroscopy (EIS) test is carried out in 3.5wt% NaCl solution, and the corrosion current density is reduced by more than 60% compared with un-strengthened aluminum alloy.

[0028] Thermal stability testing: The anti-coarsening ability of nano-oxides at high temperature (particle size growth ≤5 nm after 1000℃ holding for 100h) is analyzed by differential scanning calorimetry (DSC).

[0029] Example 1 100 g of Al-5Mg alloy powder was placed in a glass bottle, 200 mL of deionized water was added, and 3.2 g of Y(NO3)3·6H2O and 2.5 g of glycine were added. After magnetic stirring for 3 h, it was transferred to a ball mill and ball milled at 400 rpm for 8 h. The suspension was rotary evaporated to dryness, sieved after vacuum drying at 100°C for 24 h. The precursor powder was placed in a tube furnace, argon was introduced, and the temperature was raised to 500°C at a rate of 10°C / min to initiate the combustion reaction. After holding for 5 min, the furnace was cooled down. The powder was cold isostatic pressed (300 MPa), followed by vacuum hot-press sintering (600°C pre-sintering + 1300°C sintering), to obtain a nano Y2O3 dispersion strengthened aluminum alloy powder. SEM showed that the oxide particle size was uniform (20 ± 5 nm), and the tensile strength reached 480 MPa.

[0030] Example 2 100 g of Al-4Cu alloy powder was placed in a glass bottle, 150 mL of ethanol was added, and 4.0 g of La(NO3)3·6H2O and 3.0 g of citric acid were added. After magnetic stirring for 4 h, it was ball milled (500 rpm, 10 h), dried by rotary evaporation, and sieved. The precursor powder was combusted in a tube furnace at a rate of 12°C / min to 550°C, held for 3 min, and then cooled. After cold isostatic pressing (320 MPa) and vacuum hot-press sintering (650°C pre-sintering + 1250°C sintering), a nano La2O3 dispersion strengthened aluminum alloy powder was obtained. TEM showed that the oxide and matrix interface was clean, and the high temperature stress rupture strength (300°C / 100h) was improved by 40% compared to the matrix.

[0031] Example 3 100 g of Al-5Mg alloy powder was placed in a glass bottle, 180 mL of deionized water was added, and 6.4 g of Y(NO3)3·6H2O and 4.0 g of glycine (φ = 1.5) were added. After ball milling (450 rpm, 12 h), it was dried and sieved. The precursor powder was combusted in a tube furnace at a rate of 15°C / min to 600°C, held for 2 min, and then cooled. After cold isostatic pressing (350 MPa) and vacuum hot-press sintering (600°C pre-sintering + 1350°C sintering), a high-density nano Y2O3 dispersion strengthened aluminum alloy powder was obtained. DSC showed that the oxide particle size only increased by 3 nm at 1000°C, and the thermal stability was significantly better than that of the mechanical mixing method.

[0032] Example 4 100 g of Al-4Cu alloy powder was placed in a glass bottle, 200 mL of deionized water was added, and 2.0 g of Y(NO3)3·6H2O and 1.5 g of glycine (φ = 0.8) were added. After ball milling (300 rpm, 6 h), it was dried and sieved. The precursor powder was burned in a tube furnace at 8°C / min to 400°C, and after holding for 8 min, it was cooled. After cold isostatic pressing (250 MPa), vacuum hot pressing sintering (550°C presintering + 1200°C sintering) was performed to obtain a low-cost nano Y2O3 dispersed strengthened aluminum alloy powder. Electrochemical tests show that the corrosion current density is reduced to 0.1 μA / cm 2 , and the seawater corrosion resistance is excellent.

Claims

1. A method for preparing nano-oxide dispersion-strengthened aluminum alloy powder, characterized in that: It includes raw material preparation, precursor preparation, in-situ reaction and sintering.

2. The preparation method according to claim 1, characterized in that, The titanium alloy powder is selected from at least one of Al-Si-10Mg, Al-Cu or pure aluminum powder, with an average particle size of 10-50 μm.

3. The preparation method according to claim 1, characterized in that, The molar ratio (fuel ratio Φ) of the organic fuel to the metal salt additive is 0.5-2.0, and the combustion reaction temperature and the size of the nano-oxide particles (10-100nm) are controlled by adjusting the Φ value.

4. The preparation method according to claim 1, characterized in that, The gases released during the self-propagating combustion reaction include CO2, N2, or H2O, which enable in-situ dispersion and pore structure regulation of nano-oxides through gas escape.

5. The preparation method according to claim 1, characterized in that, The nano-oxides in the sintered aluminum alloy are at least one of Y2O3, Al2O3 or TiO2, with a volume fraction of 0.5%-5%, and the interfacial bonding strength with the matrix is ​​≥50MPa.

6. The preparation method according to claim 1, characterized in that, The tensile strength of the aluminum alloy block material is ≥450MPa, and its high-temperature creep strength at 300℃ is 20%-40% higher than that of the unstrengthened alloy.

7. An aluminum alloy material prepared by the method according to any one of claims 1-6, characterized in that, The material contains nano-oxide particles that are dispersedly distributed with a particle size of 10-50 nm, and the material has a relative density of ≥98% and an oxygen content of ≤0.2 wt%.

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