Preparation method of porous magnesium alloy, porous magnesium alloy and preparation system

Abstract

The embodiment of the invention relates to a preparation method of a porous magnesium alloy, the porous magnesium alloy and a preparation system.The preparation method comprises the steps that a CMT welding method is utilized, magnesium alloy additive preparation is conducted on the surface of a base plate on the basis of magnesium alloy welding wires, water is synchronously applied to the bottom of a welding bead, and water at the bottom of molten drops forms water vapor; the preparation method of the porous magnesium alloy is simple, the preparation speed is high, the problem that the forming size and the structure are limited is solved, and the porous magnesium alloy with the porous structure and the magnesium oxide micro-nano particles distributed in a dispersed mode is obtained. The porous magnesium alloy can be continuously and rapidly prepared in a high-degree-of-freedom and customized mode.

Description

Technical Field

[0001] The present application relates to the technical field of magnesium alloys, and more specifically, to a method for preparing a porous magnesium alloy, a porous magnesium alloy and a preparation system. Background Art

[0002] Magnesium alloy is the lightest metal structural material in current engineering applications. Due to its remarkable lightweight effect, it is increasingly widely used in aerospace, rail transit, national defense, military industry, and biomedicine. Porous metal or foam metal materials have a special structure and have the characteristics of both metal and pores, such as low density, large specific surface area, sound absorption, sound insulation, shock absorption, impact energy absorption, and good electromagnetic shielding performance. They also have broad application prospects in the industrial field. The preparation of magnesium alloy into porous materials can give full play to the advantages of magnesium alloy and porous metal, so that magnesium alloy can show better thermal physical properties, damping performance, sound absorption performance, biocompatibility performance, etc., which is conducive to the integrated development of its structure and function, and further broadens the application field of magnesium alloy.

[0003] At present, the preparation of porous magnesium alloys mainly adopts melt foaming method, infiltration casting method, investment casting method, powder metallurgy method, etc. However, magnesium alloys have high chemical activity, are easy to burn, and have poor porosity. The preparation of porous magnesium alloys in liquid state has high requirements for experimental equipment and safety protection. The preparation of porous magnesium alloys by powder metallurgy also has problems such as high cost, limited forming size and structure, complex process, poor mechanical properties and corrosion resistance. Summary of the invention

[0004] The present application is provided to solve the above-mentioned defects existing in the prior art. A preparation method of a porous magnesium alloy, a porous magnesium alloy and a preparation system are needed, which do not require complicated and costly preparation steps, have a simple preparation method and a fast preparation speed, overcome the problem of limited molding size and structure, and can continuously and quickly prepare porous magnesium alloys with high degree of freedom and customization.

[0005] In a first aspect of the present application, a method for preparing a porous magnesium alloy is provided, the preparation method comprising: using a CMT welding method to perform additive preparation of a magnesium alloy on the surface of a substrate based on a magnesium alloy welding wire, and simultaneously applying water to the bottom of the weld so that the water at the bottom of the molten droplet forms water vapor, and the magnesium melt reacts with the water vapor to obtain hydrogen and magnesium oxide, and after solidification, a porous magnesium alloy having a porous structure and dispersed magnesium oxide micro-nano particles is obtained.

[0006] In a second aspect of the present application, a porous magnesium alloy obtained by the preparation method described in any embodiment of the present application is provided.

[0007] According to a third aspect of the present application, a system for preparing a porous magnesium alloy is provided, the system comprising a CMT welding machine and a water supply device, the CMT welding machine comprising a welding gun, the water supply device comprising a nozzle, the nozzle being coaxially arranged with the end of the welding gun, and the spraying direction of the nozzle being opposite to the bottom of the weld so as to synchronously deliver water to the bottom of the weld.

[0008] The preparation methods, porous magnesium alloys and preparation systems provided in various embodiments of the present application are carried out using CMT based on magnesium alloy welding wire. The CMT additive preparation technology has low heat input and is suitable for the preparation of porous magnesium alloy materials. Only the welding wire and the CMT welding machine need to be matched, and additive preparation can be carried out along the weld to obtain porous magnesium alloys of different sizes, overcoming the problem of limited forming size and making the preparation more flexible. The preparation does not require the aid of foaming agents and viscosity enhancers, and the method is simpler and the preparation speed is fast, which can achieve low-cost, high-degree-of-freedom, customized continuous and rapid preparation of porous magnesium alloys. It can be applied to any composition magnesium alloy welding wire for additive preparation of porous magnesium alloys. The preparation of magnesium alloy gradient pore size porous structure and porous sandwich magnesium alloy materials can also be achieved by real-time adjustment of the water flow rate. Therefore, the preparation method of the porous magnesium alloy provided in the present application can have a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the drawings, which are not necessarily drawn to scale, the same reference numerals may describe similar parts in different views. The same reference numerals with letter suffixes or different letter suffixes may represent different instances of similar parts. The accompanying drawings generally illustrate various embodiments by way of example and not limitation, and together with the specification and claims, are used to illustrate the embodiments applied for. When appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the present apparatus or method.

[0010] Figure 1 A schematic diagram showing a method for fixing a nozzle and a CMT welding gun during an additive manufacturing process according to an embodiment of the present application is shown; Figure 2 A cross-sectional structure diagram of a porous magnesium alloy according to Example 1 of the present application is shown; Figure 3 A longitudinal cross-sectional structure diagram of a porous magnesium alloy according to Example 1 of the present application is shown; Figure 4 A block structure diagram of a porous magnesium alloy according to Example 1 of the present application is shown; Figure 5 A cross-sectional structure diagram of a porous magnesium alloy according to Example 2 of the present application is shown; Figure 6 A longitudinal cross-sectional structure diagram of a porous magnesium alloy according to Example 2 of the present application is shown; Figure 7 A block structure diagram of a porous magnesium alloy according to Example 2 of the present application is shown; Figure 8 A cross-sectional structure diagram of a porous magnesium alloy according to Example 3 of the present application is shown; Fig. 9 A longitudinal cross-sectional structure diagram of a porous magnesium alloy according to Example 3 of the present application is shown; Fig.10 A block structure diagram of a porous magnesium alloy according to Example 3 of the present application is shown; Fig.11 A cross-sectional structure diagram of a porous magnesium alloy according to Example 4 of the present application is shown; Fig.12 A longitudinal cross-sectional structure diagram of a porous magnesium alloy according to Example 4 of the present application is shown; Fig.13 A block structure diagram of a porous magnesium alloy according to Example 4 of the present application is shown; Fig.14 A diagram showing that the porous magnesium alloy according to Example 4 of the present application floats on the water surface. DETAILED DESCRIPTION

[0011] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application is described in detail below in conjunction with the accompanying drawings and specific implementation examples. The embodiments of the present application are further described in detail below in conjunction with the accompanying drawings and specific implementation examples, but are not intended to limit the present application.

[0012] The words "first", "second" and similar words used in this application do not indicate any order, quantity or importance, but are only used to distinguish. The words "include" or "comprise" and similar words mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of including other elements.

[0013] According to an embodiment of the present application, a method for preparing a porous magnesium alloy is provided, and the preparation method includes: using a CMT (metal transition technology) welding method to prepare a magnesium alloy additive on the surface of a substrate based on a magnesium alloy welding wire, and simultaneously applying water to the bottom of the weld so that the water at the bottom of the molten droplet forms water vapor, and the magnesium melt reacts with the water vapor to obtain hydrogen and magnesium oxide, and after solidification, a porous magnesium alloy with a porous structure and dispersed magnesium oxide micro-nano particles is obtained.

[0014] When CMT is used to add materials, the water vapor produced by the instantaneous evaporation of water at the bottom of the droplet reacts with the magnesium melt: Mg (s) +H2O (g) →MgO (s) +H 2(g)A large amount of hydrogen is generated in a short time and dispersed in the molten pool without time to escape, and the porous magnesium alloy is prepared in conjunction with the cooling and solidification of the molten pool.

[0015] The hydrogen formed by the reaction of magnesium melt and water vapor dissolves and disperses in the melt. During the solidification of magnesium melt, bubbles form in the melt through homogeneous nucleation, heterogeneous nucleation at the inclusion plane interface, and heterogeneous nucleation and growth in conical pits, so that worm-like pores are finally formed inside the magnesium melt. The magnesium oxide micro-nanoparticles obtained by the reaction of magnesium melt and water vapor are dispersed in the porous magnesium alloy, which can improve the strength of the porous magnesium alloy. Under the three nucleation modes, the critical radius formula of bubble nucleation is: in, R is the critical nucleation radius of the bubble; is the liquid / gas interface energy; is the gas pressure above the melt; is the static pressure of the melt at the bubble; is the melt density; g = 9.8m / s 2 is the acceleration due to gravity; is the depth of the bubble in the melt. However, the nucleation work required by the system to overcome is different under different bubble nucleation modes. The pressure inside the bubble after bubble nucleation P H-C (Growth force) greater than the pressure outside the bubble P re (growth resistance), the bubbles will grow.

[0016] Since the principle of obtaining porous magnesium alloy by the preparation method of the present application is the reaction between molten droplets and water vapor, even if the composition of the magnesium alloy welding wire is different, it will not affect the formation of porosity. Therefore, it can be applied to magnesium alloy welding wire of any composition for porous magnesium alloy additive preparation.

[0017] Therefore, compared with the existing melt foaming method, infiltration casting method, investment casting method, powder metallurgy method, etc., the preparation method of the porous magnesium alloy of the present application is easier to control, does not require the aid of foaming agents, viscosity enhancers, and does not require complicated operating steps. The preparation method is simpler and easier to operate; the preparation method of the porous magnesium alloy of the present application has a low preparation cost, which is conducive to wide use; the preparation method of the porous magnesium alloy of the present application only needs to change the conditions of additive preparation to meet different needs, and realize high-degree-of-freedom preparation and customized preparation of porous magnesium alloys; the preparation of magnesium alloys based on the CMT welding method is less restricted, the preparation process is faster, and continuous preparation of porous magnesium alloys can be achieved.

[0018] The present application utilizes metal transition technology to accumulate molten magnesium alloy in the process of melting the welding wire to form an additive with high degree of freedom, so as to obtain the desired shape and structure of the additive, thus overcoming the problem of limited molding size and structure.

[0019] In some embodiments, the magnesium alloy welding wire has a diameter of 1.2-2.0 mm, and the required additive is obtained by combining the conditions of the CMT welding process and the flow rate of the delivered water.

[0020] In some embodiments, the welding speed of the CMT welding method during the preparation process is 50-70 cm / min; the wire feeding speed is 7.5-9.5 m / min.

[0021] In some embodiments, the welding voltage of the CMT welding method during the preparation process is 15-20V; the current is 125-135A; and the heat input is 1500-2000J / cm. The heat input during the CMT additive preparation process is low, which is suitable for the preparation of porous magnesium alloy materials.

[0022] In some embodiments, during the preparation process, the welding wire extends out of the welding gun by 10 to 15 mm.

[0023] In some embodiments, the tail end of the welding wire is 2-5 mm away from the highest point of the additive plane, so that the welding wire forms an additive.

[0024] In some embodiments, the water flow rate of the water applied to the bottom of the weld during the preparation process is 15-50 ml / min. The porous gradient structure of the magnesium alloy and the porous sandwich porous magnesium alloy material can also be prepared by controlling the water flow rate. It can be obtained through experiments that the preparation of a porous magnesium alloy with a porosity of 10%-45% can be achieved by adjusting the water flow rate.

[0025] In some embodiments, the protective gas flow rate during the preparation process is 12-18 L / min.

[0026] According to an embodiment of the present application, there is also provided a porous magnesium alloy obtained by the preparation method described in any embodiment of the present application.

[0027] According to an embodiment of the present application, a preparation system for porous magnesium alloy is also provided. The preparation system includes a CMT welder and a water supply device. The CMT welder includes a welding gun. The water supply device includes a nozzle. The nozzle is coaxially arranged with the end of the welding gun, and the spraying direction of the nozzle is opposite to the bottom of the weld bead, so as to synchronously deliver water to the bottom of the weld bead. The water flow rate sprayed by the nozzle is 15-50 ml / min.

[0028] The CMT welding machine in the following embodiments is a Fronius TPS500i CMT welding machine. The water supply device includes a water pump, a water tank, a pressure controller and a nozzle, and the nozzle is coaxially fixed to the front end of the CMT welding gun (such as Figure 1 As shown in the figure, the water supply system can synchronously supply water to the bottom of the weld during the CMT additive manufacturing process.

[0029] Example 1 The magnesium alloy substrate was polished, and then acetone was used as the cleaning medium to ultrasonically clean and collect the treated substrate; the water supply device was started, and the CMT welder was started to perform additive preparation on the substrate. The conditions during the CMT welding process were: AZ31 magnesium alloy welding wire, welding wire diameter 1.2mm, welding speed: 60cm / min, wire feeding speed: 8m / min, welding voltage: 16V, current: 130A, heat input: 1600J / cm, shielding gas flow: 15L / min, and the shielding gas was high-purity argon. During the CMT additive process, water was supplied synchronously to the bottom of the weld, and the water flow rate was 15ml / min. The cross-section of the obtained porous magnesium alloy is shown in the figure. Figure 2 As shown, the longitudinal section Figure 3 As shown, the porous magnesium alloy block is Figure 4 As shown, through Figure 2 , Figure 3 and Figure 4 It can be seen that the interior of the porous magnesium alloy presents an irregular porous structure.

[0030] Example 2 The magnesium alloy substrate was polished, and then acetone was used as the cleaning medium to ultrasonically clean and collect the treated substrate; the water supply device was started, and the CMT welder was started to perform additive preparation on the substrate. The conditions during the CMT welding process were: AZ31 magnesium alloy welding wire, welding wire diameter 1.2mm, welding speed: 60cm / min, wire feeding speed: 8m / min, welding voltage: 16V, current: 130A, heat input: 1600J / cm, shielding gas flow: 15L / min, and the shielding gas was high-purity argon. During the CMT additive process, water was supplied synchronously to the bottom of the weld, and the water flow rate was 25ml / min. The cross-section of the porous magnesium alloy obtained is shown in the figure. Figure 5 As shown, the longitudinal section Figure 6 As shown, the porous magnesium alloy block is Figure 7 As shown, through Figure 5 , Figure 6 and Figure 7 It can be seen that the interior of the porous magnesium alloy presents an irregular porous structure.

[0031] Example 3 The magnesium alloy substrate was polished, and then acetone was used as the cleaning medium to ultrasonically clean and collect the treated substrate; the water supply device was started, and the CMT welder was started to perform additive preparation on the substrate. The conditions during the CMT welding process were: AZ31 magnesium alloy welding wire, welding wire diameter 1.2mm, welding speed: 60cm / min, wire feeding speed: 8m / min, welding voltage: 16V, current: 130A, heat input: 1600J / cm, shielding gas flow: 15L / min, and the shielding gas was high-purity argon. During the CMT additive process, water was supplied synchronously to the bottom of the weld, and the water flow rate was 40ml / min. The cross-section of the porous magnesium alloy obtained is shown in the figure. Figure 8 As shown, the longitudinal section Fig. 9 As shown, the porous magnesium alloy block is Fig.10 As shown, through Figure 8 , Fig. 9 and Fig.10 It can be seen that the interior of the porous magnesium alloy presents an irregular porous structure.

[0032] Example 4 The magnesium alloy substrate was polished, and then acetone was used as the cleaning medium to ultrasonically clean and collect the treated substrate; the water supply device was started, and the CMT welder was started to perform additive preparation on the substrate. The conditions during the CMT welding process were: AZ31 magnesium alloy welding wire, welding wire diameter 1.2mm, welding speed: 60cm / min, wire feeding speed: 8m / min, welding voltage: 16V, current: 130A, heat input: 1600J / cm, shielding gas flow: 15L / min, and the shielding gas was high-purity argon. During the CMT additive process, water was supplied synchronously to the bottom of the weld, and the water flow rate was 50ml / min. The cross-section of the obtained porous magnesium alloy is shown in the figure. Fig.11 As shown, the longitudinal section Fig.12 As shown, the porous magnesium alloy block is Fig.13 As shown, through Fig.11 , Fig.12 and Fig.13 It can be seen that the interior of the porous magnesium alloy presents an irregular porous structure.

[0033] The porous magnesium alloy obtained in Example 4 was put into water to obtain Fig.14 The results shown by Fig.14 It can be seen that the porous magnesium alloy can float on the water surface, which indicates that the porous magnesium alloy prepared in Example 4 has a higher porosity and a density lower than that of water.

[0034] The porosity of the porous magnesium alloys of Examples 1 to 4 is shown in Table 1.

[0035] Table 1 Porosity of porous magnesium alloys of different embodiments Through the pore structure characteristics of the porous magnesium alloys of Examples 1 to 4 and the porosity results in Table 1, it can be obtained that as the water flow rate of the water applied in Examples 1 to 4 increases successively, the number of pores in the obtained porous magnesium alloys gradually increases, the porosity gradually increases, and the pore size also tends to increase.

[0036] In addition, although exemplary embodiments have been described herein, the scope includes any and all embodiments based on the present application with equivalent elements, modifications, omissions, combinations (e.g., various embodiments intersecting schemes), adaptations or changes. The elements in the claims are to be interpreted broadly based on the language adopted in the claims, and are not limited to the examples described in this specification or during the practice of this application, and the examples are to be interpreted as non-exclusive. Therefore, this specification and examples are intended to be considered as examples only, and the true scope and spirit are indicated by the following claims and the full scope of their equivalents.

[0037] The above description is intended to be illustrative rather than restrictive. For example, the above examples (or one or more schemes thereof) may be used in combination with each other. For example, a person of ordinary skill in the art may use other embodiments when reading the above description. In addition, in the above-mentioned specific embodiments, various features may be grouped together to simplify the present application. This should not be interpreted as an intention that a feature of an application that does not require protection is necessary for any claim. On the contrary, the subject matter of the present application may be less than all the features of an embodiment of a particular application. Thus, the following claims are incorporated herein in the specific embodiments as examples or embodiments, wherein each claim is independently a separate embodiment, and it is considered that these embodiments may be combined with each other in various combinations or arrangements. The scope of the present invention should be determined with reference to the appended claims and the full scope of equivalent forms granted by these claims.

[0038] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A method for preparing a porous magnesium alloy, characterized in that: The preparation method comprises: using a CMT welding method to perform magnesium alloy additive preparation on the surface of a substrate based on a magnesium alloy welding wire, and simultaneously applying water to the bottom of the weld so that the water at the bottom of the molten droplet forms water vapor, and the magnesium melt reacts with the water vapor to obtain hydrogen and magnesium oxide, and after solidification, a porous magnesium alloy with a porous structure and dispersed magnesium oxide micro-nano particles is obtained.

2. The preparation method according to claim 1, characterized in that: The magnesium alloy welding wire has a diameter of 1.2-2.0 mm.

3. The preparation method according to claim 1, characterized in that: During the preparation process, the welding speed of the CMT welding method is 50-70 cm / min; the wire feeding speed is 7.5-9.5 m / min.

4. The preparation method according to claim 1, characterized in that: The welding voltage of the CMT welding method during the preparation process is 15-20V; the current is 125-135A; and the heat input is 1500-2000J / cm.

5. The preparation method according to claim 1, characterized in that: During the preparation process, the welding wire extends out of the welding gun by 10~15mm.

6. The preparation method according to claim 1, characterized in that: The tail end of the welding wire is 2~5mm away from the highest point of the additive plane.

7. The preparation method according to claim 1, characterized in that: During the preparation process, the water flow rate applied to the bottom of the weld is 15~50ml / min.

8. The preparation method according to claim 1, characterized in that: The protective gas flow rate during the preparation process is 12~18L / min.

9. The porous magnesium alloy obtained according to the preparation method according to any one of claims 1 to 8.

10. A system for preparing a porous magnesium alloy, characterized in that: The preparation system includes a CMT welder and a water supply device, wherein the CMT welder includes a welding gun, and the water supply device includes a nozzle, wherein the nozzle is coaxially arranged with the end of the welding gun, and the spraying direction of the nozzle is opposite to the bottom of the weld, so as to synchronously supply water to the bottom of the weld.

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