A magnesium alloy powder containing an sb element for laser selective melting and application thereof

Abstract

The application belongs to the field of laser selective melting rapid forming, and discloses a magnesium alloy powder containing Sb element for laser selective melting and application of the magnesium alloy powder, the magnesium alloy powder for laser selective melting is composed of the following components with mass percentage: Al element: 8.5-9.5%, Zn element: 0.5-0.9%, Mn element: 0.2-0.4%, Sb element: 0.1-0.5%, impurities: ≤0.1%, and the rest is Mg element. The application improves the specific composition of the magnesium alloy powder for laser selective melting, introduces Sb element into the magnesium alloy, cooperates with the SLM process, and correspondingly obtains the SLM magnesium alloy forming piece, which has the characteristics of high yield strength and prolonged creep life, effectively improves the strength of the magnesium alloy forming piece, and deepens the application of the magnesium alloy in the SLM process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of laser selective melting rapid prototyping, and more particularly relates to a magnesium alloy powder containing Sb element for laser selective melting and application thereof. BACKGROUND

[0002] The laser selective melting technology (SLM) is a kind of 3D printing technology, and is a main technical approach in metal material additive manufacturing. It breaks the traditional tool, fixture and machine tool processing mode, and according to the three-dimensional model data of a part or object, the metal powder is rapidly melted and solidified through a forming equipment, and then a part entity is formed layer by layer. Compared with the traditional processing technology, the laser selective melting shows a series of advantages such as being able to prepare complex structural parts, high forming precision, high material utilization rate, etc., and is widely used in the fields of aviation, aerospace and automobile industry. At present, the SLM technology is relatively mature in iron, titanium, nickel-based high-temperature alloy, aluminum alloy, etc., and has been widely applied. The magnesium alloy is increasingly widely researched in the field of SLM due to its low density, high specific strength, good biocompatibility and other advantages.

[0003] Magnesium (Mg) is the eighth most abundant element in the earth's crust, which is 33% lighter than aluminum, 60% lighter than titanium, and 75% lighter than steel. The magnesium alloy composed of other elements also has the outstanding advantages of small density, high specific strength, large elastic modulus, good thermal conductivity and shock absorption, strong electromagnetic shielding performance, good biocompatibility, easy recycling, etc. The magnesium alloy is the lightest metal material in practical application, and is known as the "green structural material in the 21st century", and is also marked by many industry experts as one of the star materials in the future metal industry. Compared with aluminum alloy, steel and iron, the magnesium alloy has a lower elastic modulus, and can consume more deformation work under the same stress condition, has the functions of noise reduction and vibration reduction, and can bear a larger impact vibration load. However, the absolute strength of the magnesium alloy is relatively low, and the creep life is short. For example, the yield strength of the AZ91D magnesium alloy obtained by casting is 150 MPa, and the creep life is 260-270 h, which limits the development of the magnesium alloy in the laser selective melting technology. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the purpose of the present application is to provide a magnesium alloy powder containing Sb element for laser selective melting and application thereof. By improving the specific composition of the magnesium alloy powder for laser selective melting, the Sb element is introduced into the magnesium alloy, and the SLM process is used, so that the SLM magnesium alloy forming part obtained accordingly has the characteristics of high yield strength and prolonged creep life, effectively improves the strength of the magnesium alloy forming part, and deepens the application of the magnesium alloy in the SLM process.

[0005] To achieve the above object, according to one aspect of the present application, a kind of magnesium alloy powder for laser selective melting is provided, characterized by the following mass percentage components: Al element: 8.5-9.5%, Zn element: 0.5-0.9%, Mn element: 0.2-0.4%, Sb element: 0.1-0.5%, impurities: ≤0.1%, and the rest is Mg element.

[0006] According to another aspect of the present application, the present application provides a preparation method of the above-mentioned magnesium alloy powder for laser selective melting, characterized by comprising the following steps:

[0007] S1: antimony ingot is atomized to obtain antimony powder, and the particle size of the antimony powder is 15-53 μm;

[0008] S2: using a raw material magnesium alloy containing Al element, Zn element and Mn element as a raw material, a raw material magnesium alloy powder is prepared, and the particle size of the raw material magnesium alloy powder is 15-53 μm; then, the raw material magnesium alloy powder and the antimony powder are separately subjected to drying treatment, so that the powders are fully dried;

[0009] S3: the raw material magnesium alloy powder and the antimony powder after drying are proportioned and mixed according to the target mass percentage of each component in the magnesium alloy powder for laser selective melting, and the mixing is specifically carried out by powder mixing treatment, so as to obtain the target magnesium alloy powder for laser selective melting.

[0010] As a further preferred embodiment of the present application, in step S2, the drying treatment of each powder is specifically carried out by drying the powder in a vacuum drying oven at 60°C for 4-5 h;

[0011] In step S3, after the powder mixing treatment, the magnesium alloy powder for laser selective melting is further subjected to ball milling treatment.

[0012] According to still another aspect of the present application, the present application provides the application of the above-mentioned magnesium alloy powder for laser selective melting in laser selective melting.

[0013] As a further preferred embodiment of the present application, it specifically comprises the following steps:

[0014] (1) drying treatment is carried out on the magnesium alloy powder for laser selective melting, and the substrate is preheated at the same time;

[0015] (2) using the magnesium alloy powder for laser selective melting, laser selective melting is carried out in an inert atmosphere, and the laser selective melting adopts a strip scanning strategy to obtain a magnesium alloy shaped part by layer-by-layer scanning.

[0016] As a further preferred embodiment of the present application, in the step (2), the process parameters of the laser selective melting are set as follows: laser power is 50-200 W, scanning speed is 200-500 mm / s, layer thickness is 30-40 mu m, and scanning pitch is 80-120 mu m.

[0017] As a further preferred embodiment of the present application, in the step (1), the preheating temperature used in the preheating is 100-200 DEG C.

[0018] As a further preferred embodiment of the present application, in the step (2), the inert atmosphere is an argon atmosphere.

[0019] Preferably, the oxygen content of the molding cavity corresponding to the laser selective melting is less than 200 ppm.

[0020] More preferably, the inert atmosphere is a pure argon atmosphere.

[0021] According to another aspect of the present application, the present application provides a magnesium alloy formed part obtained by the above application.

[0022] Compared with the prior art, the magnesium alloy powder for laser selective melting obtained by the present application has the following mass percentage composition: Al: 8.5-9.5%, Zn: 0.5-0.9%, Mn: 0.2-0.4%, Sb: 0.1-0.5%, impurities: ≤0.1%, and the rest is Mg. Based on the present application, the addition of antimony element can be carried out by a powder mixing method, for example, the prepared raw material magnesium alloy powder and antimony powder can be fully mixed in a powder mixing device. Unlike other magnesium alloys in the prior art, which do not contain Sb element, the present application improves the strength of the magnesium alloy, improves the mechanical properties of the magnesium alloy, and prolongs the creep life of the magnesium alloy part, thereby providing a new idea for the development of laser selective melting technology in the field of printing magnesium alloy.

[0023] The magnesium alloy powder for laser selective melting in the present application can be used to print parts with high strength and long creep life. After laser selective melting printing, compared with magnesium alloys without Sb element, the magnesium alloy formed part obtained by the present application has the characteristics of high strength. By adding an appropriate amount of Sb element (Sb has very low solubility in Mg) to the magnesium alloy, the present application can generate intermetallic compound Mg3Sb2 in the alloy, which has good thermal stability and is dispersedly distributed in the alloy, thereby playing a dispersion strengthening role and filling the performance weakness caused by the lack of strengthening phase Mg17Al12 in magnesium aluminum alloy, thereby improving the strength of the magnesium alloy. By strictly controlling the addition amount of Sb element and strictly controlling the mass percentage of Sb element in the magnesium alloy system to be 0.1-0.5%, the present application effectively ensures the strengthening effect of the magnesium alloy.

[0024] The laser selective melting preferably adopted in the present application has a laser power of 50-200 W, a scanning speed of 200-500 mm / s, a layer thickness of 30-40 μm, a scanning interval of 80-120 μm, and adopts a strip scanning strategy to obtain the target magnesium alloy part, and especially a magnesium alloy forming part with high density (in the following Example 2, the density can reach 99.46%) can be obtained, further ensuring the improvement of the yield strength and the creep life. Moreover, similar to the SLM process known in the prior art, the present application can further improve the thermal process in the printing process through preheating treatment and a strip scanning strategy, further effectively reducing the size of the residual stress generated in the printing process, thereby further improving the quality of the formed part. In addition, considering that the SLM process known in the prior art has a better SLM process effect when the particle size of the powder raw material used is 15-53 μm, therefore, the particle size of the various powders in the present application can be preferably 15-53 μm (which can be realized by sieving).

[0025] In summary, the present application improves the mechanical properties and the life of the SLM magnesium alloy forming part by adding Sb element to the magnesium-aluminum alloy, making the mass percentage of Sb element in the magnesium alloy system 0.1-0.5%, and cooperating with the SLM process, thereby providing a direction for improving the strength of the magnesium alloy used for selective laser melting. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a flow chart of the preparation method of the magnesium alloy powder for laser selective melting provided by the preferred embodiment of the present application and the printing process of applying the powder to laser selective melting.

[0027] Figure 2 is the yield strength measured by the samples obtained in each embodiment (corresponding to Sb mass fraction of 0.1%, 0.3%, 0.5% respectively) and each comparative example (corresponding to Sb mass fraction of 0, 1.0% respectively) in the present application. The abscissa in the figure is the mass fraction of Sb element in the magnesium alloy obtained by each sample.

[0028] Figure 3 、 Figure 4 、 Figure 5 are the stress-strain diagrams measured by the samples of Examples 1, 2 and 3 respectively. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0030] AsFigure 1 As shown, the embodiment of the present application provides a preparation method of magnesium alloy powder for laser selective melting and a printing process of applying the powder to laser selective melting, specifically comprising the following steps:

[0031] (a) The preparation of the magnesium alloy powder for laser selective melting technology comprises the following steps:

[0032] Step one, high-quality antimony powder is prepared by using gas atomization technology on antimony ingot, and the particle size is 15-53 μm. The antimony powder can be treated by ball milling to obtain spherical or quasi-spherical powder particles.

[0033] Step two, the magnesium alloy powder (the particle size is also required to be 15-53 μm) and the antimony powder are dried before mixing to fully dry the powder, and the specific operation is: drying in a vacuum drying oven at 60°C for 4-5 h;

[0034] Step three, the antimony element is added by a powder mixing method, the prepared alloy powder is placed in a powder mixing device for sufficient mixing to obtain the magnesium alloy powder for laser selective melting technology.

[0035] Further, the prepared magnesium alloy has a mass percentage composition of Al: 8.5-9.5%, Zn: 0.5-0.9%, Mn: 0.2-0.4%, Sb: 0.1-0.5%, and other unavoidable impurities (such as Si, Fe, Cu, Ni, etc.): ≤0.1%, and the rest is Mg.

[0036] (b) The printing process of the magnesium alloy powder for laser selective melting comprises the following steps:

[0037] Step one, the alloy powder is dried before printing, and the substrate is preheated;

[0038] Step two, in an inert atmosphere environment, the oxygen content in the printing chamber is less than 200 ppm, printing is performed according to the set parameters, a strip scanning strategy is adopted, and a high-strength magnesium alloy part is obtained by layer-by-layer scanning.

[0039] Further, the parameters of the laser selective melting process are: laser power is 50-200 W, scanning speed is 200-500 mm / s, layer thickness is 30-40 μm, and scanning pitch is 80-120 μm.

[0040] Further, in the laser selective melting process of printing the magnesium alloy, the preheating temperature in step one is 100-200°C.

[0041] Further, in the laser selective melting process of printing the magnesium alloy, the inert atmosphere in step two is a pure argon atmosphere.

[0042] The following are specific examples (where the antimony powder raw materials used are all prepared by gas atomization from the same batch of antimony ingots according to the prior art, and the gas atomized AZ91D powder used is also from the same batch):

[0043] Example 1

[0044] The preparation method and printing process of the magnesium alloy powder for laser selective melting are as follows:

[0045] (1) Mix the gas atomized AZ91D powder with the antimony powder at a mass ratio of 999:1. Dry the mixed powder before mixing: dry in a vacuum drying oven at 60 degrees Celsius for 5 hours;

[0046] (2) Add the antimony element by the powder mixing method. Put the prepared powder in step (1) into the powder mixing device and mix thoroughly to obtain a magnesium alloy powder for laser selective melting technology;

[0047] The corresponding laser selective melting magnesium alloy powder is composed of the following mass percentages of elements:

[0048] Al: 8.5%, Zn: 0.5%, Mn: 0.2%, Sb: 0.1%, impurities: 0.05%, and the rest is Mg.

[0049] (3) Dry the powder prepared in step (2) before printing, and preheat the substrate to a temperature of 200 degrees Celsius;

[0050] (4) Print according to the set parameters in a pure argon atmosphere. The parameters of the laser selective melting process are: laser power is 60W, scanning speed is 200mm / s, layer thickness is 30μm, scanning interval is 100μm, and strip scanning strategy is used to scan layer by layer to obtain high-strength magnesium alloy parts;

[0051] (5) The yield strength of the parts prepared by this method is 158Mpa, and the creep life is 408h. Compared with traditional AZ91D magnesium alloy, the yield strength and creep life are increased by 5% and 51% respectively.

[0052] Example 2

[0053] The preparation method and printing process of the magnesium alloy powder for laser selective melting are as follows:

[0054] (1) Mix the gas atomized AZ91D powder with the antimony powder at a mass ratio of 332:1. Dry the mixed powder before mixing: dry in a vacuum drying oven at 60 degrees Celsius for 5 hours;

[0055] (2) The antimony element is added by a powder mixing method, and the powder prepared in step (1) is fully mixed in a powder mixing device to obtain a magnesium alloy powder for laser selective melting technology;

[0056] The corresponding obtained laser selective melting magnesium alloy powder is composed of the following mass percentages of elements:

[0057] Al: 9.0%, Zn: 0.7%, Mn: 0.3%, Sb: 0.3%, impurities: 0.05%, and the rest is Mg.

[0058] (3) The powder prepared in step (2) is dried before printing, and the substrate is preheated, and the preheating temperature is 200°C;

[0059] (4) Printing is performed according to the set parameters in a pure argon atmosphere, and the parameters of the laser selective melting process are: laser power is 60W, scanning speed is 200mm / s, layer thickness is 30μm, scanning interval is 100μm, and strip scanning strategy is adopted to obtain high-strength magnesium alloy parts by layer-by-layer scanning;

[0060] (5) The yield strength of the part prepared by this method is 173Mpa, and the creep life is 590h, which is 15% and 119% higher than that of the traditional AZ91D magnesium alloy, respectively.

[0061] Example 3

[0062] The preparation method and printing process of the laser selective melting magnesium alloy powder are as follows:

[0063] (1) The gas-atomized AZ91D powder and antimony powder are mixed in a mass ratio of 199:1, and the powder is dried before mixing: dried in a vacuum drying oven at 60°C for 5 hours;

[0064] (2) The antimony element is added by a powder mixing method, and the powder prepared in step (1) is fully mixed in a powder mixing device to obtain a magnesium alloy powder for laser selective melting technology;

[0065] The corresponding obtained laser selective melting magnesium alloy powder is composed of the following mass percentages of elements:

[0066] Al: 9.0%, Zn: 0.5%, Mn: 0.4%, Sb: 0.5%, impurities: 0.05%, and the rest is Mg.

[0067] (3) The powder prepared in step (2) is dried before printing, and the substrate is preheated, and the preheating temperature is 200°C;

[0068] (4) In a pure argon atmosphere, printing is carried out according to the parameters set, and the parameters of the laser selective melting process are: laser power is 60 W, scanning speed is 200 mm / s, layer thickness is 30 μm, scanning interval is 100 μm, and a strip scanning strategy is adopted to obtain a high-strength magnesium alloy part through layer-by-layer scanning;

[0069] (5) The yield strength of the part prepared by the method is 165 Mpa, and the creep life is 512 h, which is 10% and 90% higher than that of the traditional AZ91D magnesium alloy, respectively.

[0070] In addition, in addition to the above-mentioned examples 1-3, orthogonal experiments of different SLM process parameters are also carried out, the laser output power is changed in the range of 30-220 W with 10 W as a step, the scanning speed is changed in the range of 100-800 mm / s with 100 mm / s as a step, the layer thickness is changed in the range of 30-40 μm with 10 μm as a step, and the scanning interval is changed in the range of 60-120 μm with 20 μm as a step. The results show that when the laser power is 50-200 W, the scanning speed is 200-500 mm / s, the layer thickness is 30-40 μm, the scanning interval is 80-120 μm, and the scanning strategy is strip scanning, all have good SLM forming effect.

[0071] Comparative Example 1

[0072] The preparation method and printing process of the laser selective melting magnesium alloy powder are as follows:

[0073] (1) Directly use the gas atomized AZ91D powder, and dry the powder in a vacuum drying box at 60 degrees Celsius for 5 hours. The powder is detected by ICP and consists of the following mass percentages of elements: Al: 9.0%, Zn: 0.5%, Mn: 0.4%, no Sb element, impurities: 0.05%, and the rest is Mg.

[0074] (2) Preheat the substrate before printing, and the preheating temperature is 200 degrees Celsius;

[0075] (3) In a pure argon atmosphere, printing is carried out according to the parameters set, and the parameters of the laser selective melting process are: laser power is 60 W, scanning speed is 200 mm / s, layer thickness is 30 μm, scanning interval is 100 μm, and a strip scanning strategy is adopted to obtain a magnesium alloy part through layer-by-layer scanning;

[0076] (4) The yield strength of the part prepared by the method is 146 Mpa, and the creep life is 262 h, which is similar to the traditional cast magnesium alloy AZ91D.

[0077] Comparative Example 2

[0078] The preparation method and printing process of the laser selective melting magnesium alloy powder are as follows:

[0079] (1) The gas-atomized AZ91D powder is mixed with antimony powder at a mass ratio of 99:1, and drying treatment is performed before powder mixing: drying in a vacuum drying box at 60 degrees Celsius for 5 hours;

[0080] (2) The antimony element is added by the powder mixing method, the powder prepared in step (1) is placed in the powder mixing device for sufficient mixing, and a magnesium alloy powder for laser selective melting technology is obtained;

[0081] The corresponding laser selective melting magnesium alloy powder is composed of the following mass percentages of elements:

[0082] Al: 8.5%, Zn: 0.8%, Mn: 0.3%, Sb: 1.0%, impurities: 0.05%, and the rest is Mg.

[0083] (3) The powder prepared in step (2) is dried before printing, and the substrate is preheated, and the preheating temperature is 200 degrees Celsius;

[0084] (4) Printing is performed according to the set parameters in a pure argon atmosphere, and the parameters of the laser selective melting process are as follows: laser power is 60 W, scanning speed is 200 mm / s, layer thickness is 30 μm, scanning interval is 100 μm, and a strip scanning strategy is adopted to obtain a high-strength magnesium alloy part by layer-by-layer scanning;

[0085] (5) The yield strength of the part prepared by this method is 163 MPa, and the creep life is 342 hours, although the performance is slightly improved compared with traditional magnesium alloy, the plasticity decreases greatly, and the elongation rate decreases from 7% to 2%, and the comprehensive performance decreases.

[0086] The above examples are only examples, for example, in addition to using the laser selective melting magnesium alloy powder in the present application and obtaining a magnesium alloy formed part by SLM, the powder can also be combined with other different alloy powders according to actual needs, each kind of powder corresponds to a printing area, and the preparation of a formed part with different regions and components is realized.

[0087] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for forming an SLM magnesium alloy formed part with high yield strength and extended creep life by selective laser melting, characterized in that: The specific steps include: (1) Drying the magnesium alloy powder for selective laser melting and preheating the substrate at the same time; the magnesium alloy powder for selective laser melting is composed of the following components in percentage by mass: Composition: Al element: 8.5-9.5%, Zn element: 0.5-0.9%, Mn element: 0.2-0.4%, Sb element: 0.1-0.5%, impurities: ≤0.1%, the rest is Mg element; the Sb element can play a role in dispersion strengthening during the laser printing process; (2) Using the magnesium alloy powder for laser selective melting, laser selective melting is performed in an inert atmosphere, and the laser selective melting adopts a strip scanning strategy to obtain a magnesium alloy formed part by scanning layer by layer; In step (2), the process parameters of the laser selective melting are set as follows: laser power is 50~200W, scanning speed is 200mm / s, layer thickness is 30~40μm, and scanning spacing is 80~120μm.

2. The method according to claim 1, wherein: In the step (1), the preheating temperature used in the preheating is 100-200°C.

3. The method according to claim 1, wherein: In step (2), the inert atmosphere is an argon atmosphere, and the oxygen content of the molding cavity corresponding to the laser selective melting is less than 200 ppm.

4. The method according to claim 1, wherein: In the step (2), the inert atmosphere is a pure argon atmosphere.

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