Aluminum matrix composite laser welding structure and welding method thereof

Abstract

The invention provides an aluminum matrix composite laser welding structure and a welding method thereof. The welding structure comprises a first base material, a second base material, a middle layer, a first foil layer and a second foil layer. The first base material is made of a silicon carbide particle reinforced aluminum-based composite material; the second base material is a silicon carbide particle reinforced aluminum-based composite material; the middle layer is formed by mixing and pressing modified silicon carbide particles and active metal powder; one side of the first foil material layer abuts against the first base material, and the other side of the first foil material layer abuts against the middle layer; one side of the second foil material layer abuts against the second base material, and the other side of the second foil material layer abuts against the middle layer. The structure of the weld joint can be effectively improved, welding defects are reduced, and the connection strength and overall performance of the weld joint are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of welding, more particularly to an aluminum-based composite material laser welding structure and a welding method thereof. BACKGROUND

[0002] With the rapid development of advanced materials in the field of aerospace manufacturing in China, SiC particle reinforced aluminum matrix composite (SiCp / Al) is widely used in the fields of aerospace, automobile manufacturing, etc. due to its high specific strength, high wear resistance and excellent thermal stability. However, due to the poor weldability of SiC particle reinforced aluminum matrix composite (SiCp / Al), the interface reaction between SiC particles and molten aluminum occurs during welding, and brittle phase Al4C3 is easily generated at high temperature, which reduces the weld toughness.

[0003] At the same time, the high laser energy density in the welding process causes partial SiC particle burning or migration and aggregation, resulting in SiC particle burning and agglomeration in the weld, forming micro defects. In addition, due to the large difference in thermal expansion coefficient between the aluminum matrix and the reinforcing particles, thermal stress cracks are easily generated during weld cooling.

[0004] The traditional laser welding method in connecting SiC particle reinforced aluminum matrix composite, the thermal stress generated during welding and the mismatch of thermal expansion coefficient between SiC particles and aluminum matrix easily lead to cracks in the weld, reducing the connection strength. The precipitation, agglomeration and gas generation of SiC particles in the molten pool are difficult to effectively discharge, which easily forms pores and inclusions, affecting the compactness and mechanical properties of the weld. The poor wettability between SiC particles and molten aluminum matrix may lead to poor interface bonding, affecting the load transfer efficiency. The welding heat affected zone may have problems such as coarse structure and reduced hardness, resulting in a decline in overall connection performance. SUMMARY

[0005] (I) Technical problems to be solved The technical problem to be solved by the present application is the problem of easy reduction of connection strength and overall connection performance when the existing laser welding method is used to connect SiC particle reinforced aluminum matrix composite.

[0006] (II) Technical solutions To achieve the above-mentioned purpose, the technical solutions adopted by the present application are: In a first aspect, the present application provides an aluminum matrix composite laser welding structure, comprising a first base material, a second base material and a foil-powder interlayer; the material of the first base material is silicon carbide particle reinforced aluminum matrix composite; the material of the second base material is silicon carbide particle reinforced aluminum matrix composite; the foil-powder interlayer comprises an intermediate layer, a first foil layer and a second foil layer; the intermediate layer is formed by mixing and pressing modified silicon carbide particles and active metal powder; one side of the first foil layer abuts against the first base material, and the other side of the first foil layer abuts against the intermediate layer; one side of the second foil layer abuts against the second base material, and the other side of the second foil layer abuts against the intermediate layer.

[0007] Preferably, the modified silicon carbide particles are silicon carbide particles coated with a nano-coating, the nano-coating is a titanium coating or a zirconium coating, and the active metal powder is titanium powder and / or zirconium powder.

[0008] Preferably, the thickness of the nano-coating is 50-200 nm.

[0009] Preferably, the first foil layer comprises at least one of a titanium foil and a zirconium foil, Preferably, the second foil layer comprises at least one of a titanium foil and a zirconium foil.

[0010] Preferably, the particle size of the modified silicon carbide particles is 0-15 μm, the mass fraction of the active metal powder in the intermediate layer is 1-5 wt%, and the particle size of the active metal powder is less than or equal to 20 μm.

[0011] In a second aspect, the present application also provides an aluminum matrix composite laser welding method for welding the aluminum matrix composite laser welding structure according to any one of the above technical solutions, the welding method comprising the following steps: S1, modifying silicon carbide particles and active metal powder are respectively prepared; S2, an intermediate layer is prepared, and the intermediate layer is assembled with a first foil layer and a second foil layer to obtain a foil-powder interlayer by pressing; S3, assembling an aluminum matrix composite laser welding structure; S4, laser welding the aluminum matrix composite laser welding structure, and obtaining a welded part after the welding is completed.

[0012] Preferably, the method further comprises the following steps: S5, performing welding quality inspection on the welding.

[0013] Preferably, step S1 comprises the following steps: obtaining modified silicon carbide particles by depositing a nano-coating on the surface of the silicon carbide particles through a magnetron sputtering or chemical vapor deposition method; 1-5wt% of active metal powder is stirred and mixed uniformly with 95-99wt% of modified silicon carbide particles.

[0014] Preferably, step S3 comprises the following steps: The foil powder sandwich is arranged between the first base material and the second base material for assembly, so that the upper surfaces of the foil powder sandwich, the first base material and the second base material are substantially flush, and the lower surfaces of the foil powder sandwich, the first base material and the second base material are substantially flush.

[0015] (Three) beneficial effects The above technical scheme of the present application has at least the following advantages: 1. The present application provides an aluminum-based composite material laser welding structure, the intermediate layer is formed by mixing and pressing modified silicon carbide particles and active metal powder, and is matched with the first foil layer and the second foil layer on both sides to form a specific foil powder sandwich. During welding, the laser beam is welded along the centerline direction of the foil powder sandwich, so that the SiC particle reinforced phase in the first base material and the second base material in the molten pool is not only blocked by the first foil layer and the second foil layer to a certain extent, but also makes the SiC particle reinforced phase far away from the small hole with the highest temperature and its adjacent area, effectively inhibiting the vaporization degree of the SiC particle reinforced phase in the base material, and to a certain extent, inhibiting the welding porosity defect. The generation of Al4C3 brittle phase is inhibited by the first foil layer (titanium foil, zirconium foil) and the second foil layer (titanium foil, zirconium foil), and instead of TiC or ZrC and other new reinforced phases, so that the welding defects are inhibited, the weld structure is more uniform, and the welding quality is further improved. In addition, the symmetrical structure of the foil powder sandwich design, the foil powder sandwich structure makes the composition and thickness of the left and right layers consistent, and cooperates with the laser parameter to control the molten pool flow, so that the SiC is uniformly dispersed to achieve the effect of optimizing the particle distribution. The weld forming is more uniform, reduces or eliminates the geometric shape mutation of the weld, and can relieve stress concentration during stress or service, thereby further improving the mechanical properties of the welded joint, especially the fatigue performance.

[0016] 2. In the present application, the intermediate layer is formed by mixing and pressing modified silicon carbide particles and active metal powder, the modified silicon carbide particles are silicon carbide particles coated with a nano coating (titanium coating or zirconium coating), and the active metal powder is titanium powder and / or zirconium powder. During welding, the laser beam is welded along the centerline direction of the intermediate layer, the active metal powder and the nano coating can avoid the direct contact of the silicon carbide particles with the laser beam, effectively inhibit the vaporization degree of the SiC particle reinforced phase in the intermediate layer, and to a certain extent, inhibit the welding porosity defect. Moreover, the introduction of the nano coating and the active metal powder makes the SiC preferentially react with Ti / Zr to form TiC / ZrC, avoids the generation of Al4C3, thereby inhibits the interface reaction, inhibits the welding defects, makes the weld structure more uniform, and further improves the welding quality.

[0017] 3、The aluminum matrix composite laser welding method can effectively improve the wettability and metallurgical bonding in the welding process of the SiC particle reinforced aluminum matrix composite, the introduction of the titanium foil and the zirconium foil of the first foil layer and the second foil layer enables the intermediate layer to form good metallurgical bonding with the first base material and the second base material, improves the connection strength of the weld, and can also optimize the fluidity of the molten pool, reduce the solidification shrinkage stress, and effectively inhibit the generation of weld cracks. The modified silicon carbide particles supplemented by the intermediate layer can be uniformly organized. The fine modified silicon carbide particles in the intermediate layer can supplement the reduced silicon carbide particles due to burning loss in the weld, and help to homogenize the distribution of the silicon carbide particles in the weld, thereby improving the hardness and wear resistance of the weld. Through the synergistic effect of the foil powder interlayer filler, the aluminum matrix composite laser welding method can significantly improve the microstructure of the SiC particle reinforced aluminum matrix composite laser welding weld, reduce welding defects, improve the mechanical properties and corrosion resistance of the weld, and improve the overall performance of the weld. The present application can significantly improve the mechanical properties of the test piece, and the tensile strength of the weld reaches 80-90% of the base material, and the elongation is increased by 25-45%.

[0018] 4、The aluminum matrix composite laser welding method provided by the present application is simple to operate, low in cost, easy to implement, and has good industrial application prospect. The present application can significantly improve the welding quality of SiCp / Al composite material, and is suitable for fields such as spacecraft load-bearing structure and new energy vehicle battery tray which have strict requirements on lightweight and reliability, and has important engineering value. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 is a structural schematic diagram of the aluminum matrix composite laser welding structure provided by the embodiments of the present application.

[0021] Figure 2 is an implementation scene diagram of the aluminum matrix composite laser welding method provided by the embodiments of the present application.

[0022] Figure 3 is an SEM diagram of the comparison of the microstructure of the conventional weld and the weld of the present application.

[0023] Figure 4 is a flowchart of the aluminum matrix composite laser welding method provided by the embodiments of the present application.

[0024] The reference signs in the drawings are as follows: 10: first base material; 20: second base material; 1: first foil material; 2: second foil material; 3: intermediate layer; 4: third foil material; 5: fourth foil material. DETAILED DESCRIPTION

[0025] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0026] It should be noted that when an element is referred to as being "fixed" or "set" on another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected or indirectly connected to the other element.

[0027] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application, and therefore cannot be understood as indicating that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0028] In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating relative importance or indicating the number of technical features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited. The specific implementation of the present application will be described in more detail below in combination with specific embodiments: As Figure 1As shown, the embodiment of the present application provides an aluminum-based composite material laser welding structure, which comprises a first base material 10, a second base material 20 and a foil powder interlayer; the material of the first base material 10 is silicon carbide particle reinforced aluminum-based composite material; the material of the second base material 20 is silicon carbide particle reinforced aluminum-based composite material; the foil powder interlayer comprises an intermediate layer 3, a first foil layer and a second foil layer; the intermediate layer 3 is formed by mixing and pressing modified silicon carbide particles and active metal powder; one side of the first foil layer abuts against the first base material 10, and the other side of the first foil layer abuts against the intermediate layer; one side of the second foil layer abuts against the second base material 20, and the other side of the second foil layer abuts against the intermediate layer. Specifically, in the embodiment, the first foil layer comprises a first foil 1 and a second foil 2, and the second foil layer comprises a third foil 4 and a fourth foil 5, wherein the first foil 1 and the second foil 2 are stacked in the thickness direction, the third foil 4 and the fourth foil 5 are stacked in the thickness direction, and the first foil 1, the second foil 2, the third foil 4 and the fourth foil 5 can be titanium foils or zirconium foils, or a combination of the two.

[0029] As shown in Figure 2 and Figure 4 , the embodiment of the present application also provides an aluminum-based composite material laser welding method for welding the aluminum-based composite material laser welding structure of any one of the above embodiments, which comprises the following steps: S1, respectively modulate modified silicon carbide particles and active metal powder; specifically, the modified silicon carbide particles are silicon carbide particles coated with a nano coating (particle size preferably 0-15 μm), and the nano coating is a titanium coating or a zirconium coating (the thickness of the nano coating is preferably 50-200 nm), and the nano coating is prepared by magnetron sputtering or chemical vapor deposition. The active metal powder is titanium powder and / or zirconium powder, the mass fraction of the active metal powder in the intermediate layer is 1-5 wt%, the particle size of the active metal powder is less than or equal to 20 μm, a micro sample is weighed using an analytical balance (accuracy 0.1 mg), and mechanical stirring or ball milling is used to ensure uniformity.

[0030] Further, the thickness of the intermediate layer of modified silicon carbide particles and active metal powder is 0.1 mm, the modulation ratio is Ti powder 2.5%, Zr powder 2.5% and modified SiC particles 95%, and the required gram weight is calculated using the following formula: Theoretical gram weight = V x p 混合 (g / m 2 ) (where p 混合 is the density of the mixture, unit: g / cm³) The theoretical gram weight under this condition is 327 g / cm 3 .

[0031] The gram weight range of different metals and addition amounts is calculated as follows: Theoretical gram weight range: 321-328 g / m².

[0032] Due to the existence of pores between actual particles, the density is usually 60-70% of the theoretical value, so the actual gram weight needs to be adjusted during the test, so: Actual gram weight = Theoretical gram weight / (0.6-0.7)≈458-547 g / m 2 During the mixing process, the density difference between the active metal powder (Ti powder, Zr powder) and the modified silicon carbide particles needs to be mechanically stirred or ball milled to ensure uniformity. When weighing, a small amount of sample needs to be weighed using an analytical balance (accuracy 0.1 mg).

[0033] S2, prepare the intermediate layer and assemble the intermediate layer with the first foil layer and the second foil layer to obtain a foil powder sandwich; specifically, according to the size of the gap of the butt joint of the first base material 10 (preferably 1-4 mm in thickness) and the second base material 20 (preferably 1-4 mm in thickness), the first foil layer and the second foil layer are cut to the corresponding size, arranged from left to right as the first foil 1, the second foil 2, the intermediate layer 3, the third foil 4, and the fourth foil 5, and the active metal powder is laser cladded on the adjacent foil layers, and then pressed to complete the preparation of the foil powder sandwich. The thickness of the first foil 1, the second foil 2, the intermediate layer 3, the third foil 4, and the fourth foil 5 is preferably 0.1-0.2 mm.

[0034] S3, assemble the aluminum matrix composite laser welding structure; specifically, the foil powder sandwich is assembled between the first base material and the second base material to make the upper surfaces of the foil powder sandwich, the first base material and the second base material substantially flush, and the lower surfaces of the foil powder sandwich, the first base material and the second base material substantially flush. The local assembly gap is not greater than Δx, and Δx is the smaller value of 10%·δ and 0.1 mm; the misalignment amount is not greater than Δy, and Δy is the smaller value of 10%·δ and 0.1 mm, and δ is the wall thickness of the first base material, which is equal to the wall thickness of the second base material.

[0035] S4, laser welding the aluminum matrix composite laser welding structure to obtain a welded part after welding. Specifically, laser in-situ welding is carried out under inert gas protection according to the set welding process parameters. The laser welding process parameters are preferably: laser power: 2000-4000 W; spot diameter: 0.2-0.5 mm; welding speed: 0.03-0.05 m / s; defocusing amount: ±3 mm; flow rate: 15-25 L / min.

[0036] S5, welding quality inspection of the welded joint. Specifically, X-ray detection, mechanical property testing and metallographic analysis are carried out after welding.

[0037] The following are specific embodiments provided in the present application: Embodiment 1: The first base material and the second base material are selected as 2mm thick SiCp / Al plate (SiC volume fraction is 15%); Step one: Prepare the welding material: 15% SiCp / 2A14 aluminum matrix composite (SiCp / 2A14) extruded plate with a size of 100mm×50mm×2mm is used as the first base material, and 15% SiCp / 2A14 aluminum matrix composite (SiCp / 2A14) extruded plate with a size of 100mm×50mm×2mm is used as the second base material for butt deep penetration welding. And use alcohol or acetone to clean the surface, remove impurities and oxides on the surface of the first base material and the second base material and the filler material.

[0038] Step two: butt joint the first base material and the second base material and fix them, pre-arrange the foil powder sandwich at the gap between the first base material and the second base material, arrange the foil powder sandwich structure in the order of first foil 1, second foil 2, middle layer 3, third foil 4, and fourth foil 5 (from left to right), use laser cladding to clad the middle layer 3 on the second foil 2 and the third foil 4, and arrange them in order and press them as a whole. The materials of each layer are as follows: First foil 1: pure titanium foil with a size of 100mm×2mm×0.1mm and a thickness of 0.01mm.

[0039] Second foil 2: pure zirconium foil with a size of 100mm×2mm×0.1mm and a thickness of 0.01mm.

[0040] Middle layer 3: a mixed layer of modified silicon carbide particles and active metal powder, wherein the particle size of the modified silicon carbide particles is 0-15μm, and the active metal powder is a mixed powder of 1-5wt% of 1:1 Ti and Zr (particle size ≤20μm). The density of the mixture is in the range of 3.22-3.28 g / cm³ (based on the theoretical density of 1-5wt% Ti and Zr), then the mass m of the middle layer 3 is: m = V×ρ 混合 = 0.02cm 3 ×(3.22 to 3.28g / cm 3 ) = 0.0644 to 0.0656g Theoretical mass range: 0.0644-0.0656g (about 64.4-65.6mg).

[0041] The actual particle packing has pores, which need to be corrected by 60-70% of the theoretical value: Actual mass = (0.0644-0.0656) / 0.65 = 0.098 to 0.102g; The actual mass range is 0.10-0.12g (about 100-120mg).

[0042] The mixed layer powder of 0.10-0.12g (about 100-120mg) is weighed by using a microbalance (with an accuracy of at least 0.1mg), and is uniformly cladded on the second foil 2 and the third foil 4 by using a laser cladding process.

[0043] The third foil 4 is a pure zirconium foil with a size of 100mmx2mmx0.1mm and a thickness of 0.01mm.

[0044] The fourth foil 5 is a pure titanium foil with a size of 100mmx2mmx0.1mm and a thickness of 0.01mm.

[0045] Step three: continuous laser welding is adopted, and the laser welding process parameters are as follows: laser power: 2000W; spot diameter: 0.2-0.5mm; welding speed: 0.03m / s; defocusing amount: 0mm; protective gas: argon, flow rate: 20L / min. During the welding process, the laser beam is focused on the surface of the test piece, and the butt joint welding method is used to obtain the welded sample and the tensile sample. The first foil 1 (titanium foil) and the first base material, the second foil 2 (zirconium foil) and the intermediate layer 3 are reacted to generate a high-temperature stable TiC phase, replace Al4C3 and reduce crack initiation. The second foil 2 (zirconium foil) and the first foil 1 (titanium foil) and the intermediate layer 3 are reacted to generate a high-temperature stable ZrC phase, replace Al4C3 and reduce crack initiation. The active metal powder and the SiC surface coating layer cooperate and react during the laser welding process to generate a high-temperature stable TiC or ZrC phase, replace the brittle phase Al4C3 generated in the traditional aluminum matrix composite laser in-situ welding. The third foil 4 (zirconium foil) and the fourth foil 5 (titanium foil) and the intermediate layer 3 are reacted to generate a high-temperature stable ZrC phase, replace Al4C3 and reduce crack initiation. The fourth foil 5 (titanium foil) and the second base material, the third foil 4 (zirconium foil) and the intermediate layer 3 are fully reacted to generate a high-temperature stable TiC phase, replace Al4C3 and reduce crack initiation. The cooperation of the foil powder interlayer during the welding process can uniformly organize, effectively improve the joint morphology and improve the overall performance of the welded joint.

[0046] Step four: after welding, non-destructive testing, mechanical property testing and metallographic analysis are carried out, the tensile strength test and microstructure analysis of the joint welded by the method of the present application are carried out, and the results show that the weld has no obvious cracks and pores, the SiC particles are uniformly distributed, and the tensile strength is increased by about 10% compared with the joint welded by the traditional method. As shown in Figure 3 Figure 3 Parts A and B are the traditional SiC particle reinforced aluminum matrix composite weld cross-section metallograph, Figure 3 ​The middle C part is a weld section metallographic picture prepared by the embodiment of the application, wherein, BM is a base material; HAZ is a heat affected zone; and WM is a weld zone. Compared with a weld of a traditional SiC particle reinforced aluminum matrix composite material, the weld provided by the application has a good fusion interface, no obvious cracks and pores, and uniform SiC particle distribution, and the problem of SiC aggregation does not exist, so that the structure of the weld is effectively improved.

[0047] The above merely describes preferred embodiments of the present application, but should not be used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An aluminum matrix composite laser welded structure, characterized by, The application relates to an aluminum matrix composite laser welding structure, which comprises: a first base material made of silicon carbide particle reinforced aluminum matrix composite material; a second base material made of silicon carbide particle reinforced aluminum matrix composite material; a foil-powder sandwich layer, which comprises an intermediate layer, a first foil layer and a second foil layer; the intermediate layer is formed by mixing and pressing modified silicon carbide particles and active metal powder; one side of the first foil layer is in abutment with the first base material, and the other side of the first foil layer is in abutment with the intermediate layer; one side of the second foil layer is in abutment with the second base material, and the other side of the second foil layer is in abutment with the intermediate layer.

2. The aluminum-based composite material laser welded structure of claim 1, wherein, The modified silicon carbide particles are silicon carbide particles coated with a nano coating, the nano coating is a titanium coating or a zirconium coating, and the active metal powder is titanium powder and / or zirconium powder.

3. The aluminum-based composite material laser welded structure of claim 2, wherein, The thickness of the nano coating is 50-200 nm.

4. The aluminum-based composite laser welded structure of claim 1, wherein, The first foil layer comprises at least one of a titanium foil and a zirconium foil, and / or the second foil layer comprises at least one of a titanium foil and a zirconium foil.

5. The aluminum-based composite laser welded structure of claim 1, wherein, The particle size of the modified silicon carbide particles is 0-15 mu m, the mass percentage of the active metal powder in the intermediate layer is 1-5 wt%, and the particle size of the active metal powder is less than or equal to 20 mu m.

6. A method of laser welding an aluminum matrix composite material, characterized by, A welding method for welding the aluminum matrix composite laser welding structure according to any one of claims 1-5, the welding method comprising the following steps: S1, respectively, modifying silicon carbide particles and active metal powder; S2, preparing an intermediate layer, and assembling the intermediate layer with a first foil layer and a second foil layer to obtain a foil-powder sandwich layer by pressing; S3, assembling the aluminum matrix composite laser welding structure; S4, laser welding the aluminum matrix composite laser welding structure, and obtaining a welded part after welding.

7. The aluminum matrix composite laser welding method of claim 6, wherein, Further comprising the following steps: S5, welding quality inspection of the welding.

8. The aluminum matrix composite laser welding method of claim 6, wherein, Step S1 comprises the following steps: Depositing a nano coating on the surface of the silicon carbide particles by a magnetron sputtering or chemical vapor deposition method to obtain modified silicon carbide particles; Stirring and uniformly mixing 1-5 wt% of active metal powder with 95-99 wt% of modified silicon carbide particles.

9. The aluminum matrix composite laser welding method of claim 6, wherein, Step S3 comprises the following steps: Placing the foil-powder sandwich layer between the first base material and the second base material for assembly, so that the upper surfaces of the foil-powder sandwich layer, the first base material and the second base material are substantially flush, and the lower surfaces of the foil-powder sandwich layer, the first base material and the second base material are substantially flush.

Images