Post-processing method for additive manufacturing AlSi10Mg alloy optical reflector

Abstract

The invention belongs to the technical field of additive manufacturing and optical reflector manufacturing, and discloses an additive manufacturing AlSi10Mg alloy optical reflector post-treatment method which comprises the steps of hot isostatic pressing treatment, friction stir treatment, surface modification layer thickness measurement, optical reflector surface machining and the like. Compared with the prior art, the post-processing method for the optical reflector has the advantages that additive manufacturing gaps can be eliminated, and the roughness of the crystal face of the reflector is remarkably reduced.

Description

Technical Field

[0001] This invention relates to a post-processing method for additive manufacturing of AlSi10Mg alloy optical mirrors, belonging to the technical fields of additive manufacturing and optical mirror manufacturing. Background Technology

[0002] Optical mirrors are core components of reflective optical systems for high-resolution deep space exploration and Earth observation satellites, and they have stringent requirements for technical specifications such as surface roughness and weight. With the increasing emphasis on weight reduction and structural strength of optical mirrors, additive manufacturing technology is being widely applied in their production. AlSi10Mg alloys possess excellent compatibility with additive manufacturing processes and are widely used in reflective optical systems. However, the additive manufacturing process inevitably creates a large number of voids, which not only reduces structural fatigue strength but also directly increases surface roughness.

[0003] In existing technologies, hot isostatic pressing (HIP) is commonly used to eliminate voids formed during additive manufacturing and improve the structural strength of mirrors. However, the inventors discovered that during HIP, the diffusion of dissolved silicon and particle agglomeration in the AlSi10Mg alloy transform submicron-sized silicon particles into micron-sized particles. Simultaneously, the matrix grains grow, leading to a decrease in hardness and exacerbating plastic deformation, crack initiation, and silicon particle shedding during precision machining, resulting in a significant increase in surface roughness. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a post-processing method for additively manufactured AlSi10Mg alloy optical mirrors. The method employs friction stir to process the crystal surfaces of the optical mirror blank after hot isostatic pressing, forming a surface modification layer that incorporates grain refinement and plastic deformation. Subsequently, the thickness of the modification layer is measured, and the optical mirror surface is precision-machined. This effectively solves the problem of increased crystal surface roughness in AlSi10Mg alloy optical mirrors caused by hot isostatic pressing, achieving the beneficial effects of eliminating additive manufacturing voids and significantly reducing the crystal surface roughness of the mirror.

[0005] The technical solution for achieving the objective of this invention is as follows:

[0006] A post-processing method for additively manufactured AlSi10Mg alloy optical mirrors includes the following steps:

[0007] Step 1: Perform hot isostatic pressing on the additively manufactured AlSi10Mg alloy optical mirror blank;

[0008] Step 2: Perform stirring and friction treatment on the surface of the mirror surface to be machined on the blank after hot isostatic pressing.

[0009] Step 3: Prepare a metallographic cross-section and measure the thickness of the surface modification layer after friction stirring treatment;

[0010] Step 4: Use rough machining to process the surfaces other than the mirror finish;

[0011] Step 5: Use precision machining to process the surface of the optical mirror.

[0012] Furthermore, in step 5, the total machining amount of the precision machining method is not greater than the thickness of the surface modification layer.

[0013] Furthermore, in step 1, the conditions for hot isostatic pressing are: temperature 300-800 ℃, pressure 70-300 MPa, holding time 1-10 h, and heating and cooling rate 2-10 ℃ / min, so as to eliminate gaps while ensuring strength.

[0014] Furthermore, in step 2, the process parameters for the friction stir treatment of the mirror surface to be processed are: rotation speed 300-1500 rpm, moving speed 20-300 mm / min, path overlap rate 50%-90%, and processing path overlap times 1-5 times, thereby refining the grains and micron-sized Si particles formed after hot isostatic pressing and improving the hardness of the surface area.

[0015] Furthermore, the optical mirror blanks are manufactured using additive manufacturing methods such as laser selective melting, laser powder bed, and electron beam melting.

[0016] Furthermore, in step 1, the conditions for hot isostatic pressing are: temperature 525 ℃, pressure 105 MPa, holding time 4 h, heating and cooling rates of 5.8 ℃ / min and 4.8 ℃ / min, respectively, which reduces porosity by more than 72% and hardness by no more than 45%.

[0017] Furthermore, in step 2, the stirring friction parameters are: rotation speed 800 rpm, moving speed 50 mm / min, path overlap rate 60%, first stirring friction is performed along one direction, then stirring friction is performed along the direction perpendicular to that direction, and finally stirring friction is performed along the same direction for the third time.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention uses hot isostatic pressing to eliminate voids formed in the additive manufacturing of AlSi10Mg alloy, which is beneficial to improving the strength of the component.

[0020] (2) The present invention uses a stirring friction method to perform surface modification treatment on the mirror surface to be processed after hot isostatic pressing, forming a surface modification layer including grain refinement and plastic deformation, and the thickness of the modification layer is obtained by metallographic measurement.

[0021] (3) The optical reflective crystal surface is processed by precision machining methods such as turning or grinding, and the machining allowance does not exceed the thickness of the modified layer. Experimental results show that the present invention can effectively reduce the surface roughness of additively manufactured AlSi10Mg alloy optical mirrors. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the method of the present invention.

[0023] Figure 2 Metallographic images of the surface modification layer of AlSi10Mg alloy using the friction stir method in this embodiment of the invention.

[0024] Figure 3 The roughness measurement results are for the AlSi10Mg alloy optical mirror without the stir friction treatment according to the embodiments of the present invention.

[0025] Figure 4 The roughness measurement results of the AlSi10Mg alloy optical mirror after friction stirring treatment according to the embodiments of the present invention are shown. Detailed Implementation

[0026] The following is in conjunction with the appendix Figure 1-4 The technical solutions of the present invention will be described in detail below with reference to the embodiments.

[0027] A post-processing method for additively manufactured AlSi10Mg alloy optical mirrors includes the following steps:

[0028] Step 1: Perform hot isostatic pressing on the additively manufactured AlSi10Mg alloy optical mirror blank;

[0029] Insufficient hot isostatic pressing (HIP) temperature and holding time significantly affect the porosity elimination effect. While extending the temperature and holding time can improve the porosity elimination effect of AlSi10Mg alloy produced by laser selective melting, it leads to coarsening of AlSi10Mg grains, precipitation of dissolved Si elements in the matrix phase to form micron-sized Si particles, resulting in decreased hardness, increased plastic deformation and tool sticking during diamond single-point turning, and ultimately increased surface roughness. Therefore, to simultaneously ensure porosity elimination and hardness, the HIP conditions are: temperature 300-800 ℃, pressure 70-300 MPa, holding time 1-10 h, and heating / cooling rate 2-10 ℃ / min.

[0030] Meanwhile, optical mirror blanks can be manufactured using additive manufacturing methods such as laser selective melting, laser powder bed, and electron beam melting.

[0031] Step 2: Perform stirring and friction treatment on the surface of the mirror surface to be machined on the blank after hot isostatic pressing.

[0032] Due to the difference in mechanical properties between the matrix phase and Si particles, cracks easily form between micron-sized Si particles and the matrix phase during diamond single-point turning, causing Si particles to detach and form pits on the AlSi10Mg alloy surface, increasing surface roughness. This step employs friction stir to modify the surface of the mirror to be machined. This refines the grains and micron-sized Si particles formed after hot isostatic pressing, increasing the hardness of the surface region. This improves plastic deformation and tool adhesion during diamond single-point turning, providing favorable conditions for obtaining a lower surface roughness.

[0033] The process parameters for friction stirring treatment of the mirror surface to be processed are: rotation speed 300-1500 rpm, moving speed 20-300 mm / min, path overlap rate 50%-90%, and processing path overlap times 1-5 times.

[0034] Step 3: Prepare a metallographic cross-section and measure the thickness of the surface modification layer after friction stirring treatment;

[0035] Step 4: Use turning or a combination of turning and grinding to process surfaces other than the mirror finish;

[0036] Step 5: Use precision machining methods such as diamond single-point turning or a combination of turning and grinding to machine the surface of the optical mirror.

[0037] Among them, the total cutting amount of turning or turning and grinding combined machining methods shall not exceed the thickness of the surface modification layer.

[0038] In step 2, the friction stirring surface treatment can also be replaced by other surface treatment methods such as ultrasonic rolling or shot peening.

[0039] Example

[0040] 1. Hot isostatic pressing treatment.

[0041] The sample used in this embodiment is an AlSi10Mg alloy billet manufactured by selective laser melting, with dimensions of φ30.0 mm and a thickness of 11.0 mm. The AlSi10Mg alloy billet was subjected to hot isostatic pressing (HIP) treatment at a temperature of 525 ℃, a pressure of 105 MPa, and a holding time of 4 h. The heating and cooling rates were 5.8 ℃ / min and 4.8 ℃ / min, respectively. Experimental verification shows that the HIP parameters selected in this embodiment can reduce porosity by more than 72%, while the hardness reduction does not exceed 45%.

[0042] 2. Friction Stir Treatment. The hot isostatic pressing (HIP) treated samples were further subjected to friction stir treatment to form a surface modification layer that incorporates grain refinement and plastic deformation effects. The friction stir parameters used were: rotation speed 800 rpm, moving speed 50 mm / min, path overlap 60%, with a first friction stir treatment along one direction, followed by a second friction stir treatment along a direction perpendicular to that direction, and finally a third friction stir treatment along the same direction.

[0043] Electron backscatter diffraction analysis showed that the average grain size of AlSi10Mg after hot isostatic pressing was 9.5 μm, and the average grain size within 0.5 mm of the surface layer after stirring and friction decreased significantly to 0.8 μm. The reduction in grain size is beneficial to the improvement of hardness and the reduction of surface roughness in diamond single-point turning.

[0044] 3. Prepare a metallographic cross-section and measure the thickness of the surface modification layer. A metallographic cross-section is prepared by section cutting and polishing, and the thickness of the surface modification layer is measured using a metallographic microscope. Figure 2 As shown, the thickness of the surface modification layer in this embodiment is 1.86-3.39 mm.

[0045] 4. No mechanical processing was performed on the non-mirror surfaces of this sample.

[0046] 5. Precision machining of the mirror surface. The optical mirror surface is machined using rough turning followed by two diamond single-point precision turning operations. The rough turning machining depth is 0.05 mm, and the two diamond single-point turning operations have machining depths of 4 μm and 2 μm, respectively.

[0047] 6. Surface roughness measurement. Figure 3 The roughness of the AlSi10Mg alloy sample without friction stir treatment is shown. Its mirror finishing method and parameters are exactly the same as those of the sample that underwent friction stir treatment. Figure 3 It can be seen that the surface roughness of the AlSi10Mg alloy optical mirror without friction stirring is Ra 8.7 nm. Figure 4 The image shows an AlSi10Mg alloy optical mirror after undergoing friction stir treatment, with a roughness of Ra 3.5 nm.

[0048] The above results show that the surface roughness of the AlSi10Mg alloy optical mirror obtained by the method of the present invention is significantly reduced.

[0049] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A post-processing method for additively manufactured AlSi10Mg alloy optical mirrors, characterized in that, Includes the following steps: Step 1: Perform hot isostatic pressing on the additively manufactured AlSi10Mg alloy optical mirror blank; Step 2: Perform stirring and friction treatment on the surface of the mirror surface to be machined on the blank after hot isostatic pressing. Step 3: Prepare a metallographic cross-section and measure the thickness of the surface modification layer after friction stirring treatment; Step 4: Use rough machining to process the surfaces other than the mirror finish; Step 5: Use precision machining to process the surface of the optical mirror.

2. The post-processing method for additive manufacturing AlSi10Mg alloy optical mirrors according to claim 1, characterized in that, In step 5, the total machining amount of the precision machining method shall not exceed the thickness of the surface modification layer.

3. The post-processing method for additively manufactured AlSi10Mg alloy optical mirrors according to claim 1, characterized in that, In step 1, the conditions for hot isostatic pressing are: temperature 300-800 ℃, pressure 70-300 MPa, holding time 1-10 h, and heating and cooling rate 2-10 ℃ / min, so as to eliminate gaps while ensuring strength.

4. The post-processing method for additively manufactured AlSi10Mg alloy optical mirrors according to claim 1, characterized in that, In step 2, the process parameters for friction stir treatment of the mirror surface to be processed are: rotation speed 300-1500 rpm, moving speed 20-300 mm / min, path overlap rate 50%-90%, and processing path overlap times 1-5 times. This refines the grains and micron-sized Si particles formed after hot isostatic pressing, thereby improving the hardness of the surface area.

5. The post-processing method for additively manufactured AlSi10Mg alloy optical mirrors according to claim 1, characterized in that, The optical mirror blanks are manufactured using laser selective melting, laser powder bed, and electron beam melting additive manufacturing methods.

6. The post-processing method for additively manufactured AlSi10Mg alloy optical mirrors according to claim 3, characterized in that, In step 1, the conditions for hot isostatic pressing are: temperature 525 ℃, pressure 105 MPa, holding time 4 h, heating and cooling rates of 5.8 ℃ / min and 4.8 ℃ / min, respectively, which reduces porosity by more than 72% and hardness by no more than 45%.

7. The post-processing method for additively manufactured AlSi10Mg alloy optical mirrors according to claim 4, characterized in that, In step 2, the stirring friction parameters are: rotation speed 800 rpm, moving speed 50 mm / min, path overlap rate 60%. The first stirring friction is performed along one direction, followed by a second stirring friction along a direction perpendicular to that direction, and finally a third stirring friction along that direction.

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