Apparatus and working method for ultrasonic-assisted SLM forming of Ti-O alloy

Abstract

This invention relates to an apparatus and method for ultrasonic-assisted SLM forming of Ti-O alloys. The apparatus includes a sealed chamber for filling with high-purity argon gas, a base platform for mounting on the base platform, an ultrasonic vibration integrated platform connected to an ultrasonic generator, a substrate for powder deposition on the base platform located above the platform, a powder-depositing mechanism on the substrate, and a laser beam generator for acting on the powder above the substrate. This apparatus and method help to alter the microstructure of the Ti-O alloy, thereby improving the forming quality and overall mechanical properties of the SLM-formed Ti-O alloy.

Description

Technical Field

[0001] This invention relates to an apparatus and a method for ultrasonic-assisted SLM forming of Ti-O alloys. Background Technology

[0002] Titanium and its alloys are widely used in the manufacture of medical implants for replacing missing tissues such as hip, knee, shoulder, and skull joints, as well as dental implants, due to their low density, high specific strength, good corrosion resistance, and excellent biocompatibility. Among existing medical titanium alloy systems, commercial pure titanium (CP-Ti) exhibits excellent biocompatibility; however, its mechanical properties are relatively low, posing a risk of fracture under long-term loads within the human body. Adding elements to prepare titanium alloys can improve their mechanical properties to meet application requirements. However, these added alloying elements (such as Al and V) release metal ions during use within the body, affecting the safety and biocompatibility of the titanium alloy. Furthermore, adding other non-toxic, neutral metal elements such as Co, Mo, and Nb to enhance mechanical properties increases cost and the complexity of the manufacturing process, further limiting the widespread application of titanium alloys. Therefore, by adding non-metallic elements such as oxygen, nitrogen, and carbon to the CP-Ti matrix in the form of interstitial atoms, the mechanical properties of CP-Ti can be significantly improved while maintaining the excellent biocompatibility of the titanium matrix at a low cost. This has become one of the important methods for researchers to enhance the mechanical strength of medical titanium alloys.

[0003] Current research on solution oxygen-strengthened titanium alloys mainly relies on preparation methods such as vacuum arc melting or powder metallurgy, followed by further shaping through cold working. However, due to the typical close-packed hexagonal structure of α-Ti, its matrix material exhibits high work hardening and relatively poor thermal conductivity. Traditional methods for forming titanium alloys present challenges such as difficulties in cutting and plastic processing, severe heat accumulation in localized deformation areas, and potential material contamination. Particularly for Ti-O materials, the dissolved oxygen atoms significantly enhance strength and work hardening, making plastic processing even more difficult. This limits the application of solution oxygen-strengthened titanium alloys in the manufacture of medical implants.

[0004] Selective laser melting (SLM) is a powder additive manufacturing process that uses a computer-controlled laser beam to melt selected areas of powder under a protective atmosphere to create products. As one of the most popular additive manufacturing technologies, SLM offers advantages in terms of high cleanliness, good forming accuracy, fine grain structure, and excellent mechanical properties in titanium alloys. It can also directly form complex shapes from difficult-to-machine metal materials. Therefore, compared to traditional processes, SLM offers significant advantages for directly fabricating customized medical titanium alloy implants. Another study indicates that SLM-produced titanium alloy samples exhibit better tribological properties than cast samples. Compared to cast samples, SLM technology, due to the high design freedom afforded by its layer-by-layer forming principle, allows for easy and one-time production of customized samples, significantly improving material utilization and shortening the manufacturing cycle. Furthermore, compared to traditional forming processes, SLM forming of titanium alloys is usually carried out in a laser work chamber filled with inert gases (such as helium and argon). This effectively avoids contamination of the titanium alloy during the forming process. At the same time, the SLM forming process has the characteristics of rapid melting, cooling and solidification, which leads to grain refinement. This gives SLM-printed titanium alloys better comprehensive mechanical properties.

[0005] However, SLM-formed titanium alloys are prone to porosity defects inside the formed samples, including circular pores and irregular incompletely melted pores, resulting in low density and affecting the overall mechanical properties of the material. The study "Influence of Layer Thickness on the Microstructure and Properties of Selective Laser Melting (SLM) Formed Ti-5Al-2.5Sn Alloy" explored the effect of SLM on the actual shape, size, and morphology of the surface texture of Ti-6Al-4V titanium alloy. It found that with a fixed laser power, the laser energy density continuously decreases with increasing layer thickness and scanning rate, leading to porosity defects, including circular pores and irregular incompletely melted pores, inside the samples with lower density.

[0006] Numerous studies have proposed the fabrication of titanium alloys using ultrasound-assisted additive manufacturing (UAM). Further research has explored incorporating high-intensity ultrasonic vibration into TC4-DT titanium alloy wire-arc direct energy deposition (SLM), finding that UAM significantly improves the grain structure of the deposited components without introducing additional porosity. The yield strength and tensile strength of the alloy are increased by 22.23% and 15.06%, respectively, compared to traditional SLM components. Furthermore, the resulting differences in lath-like α-grain structure lead to varying fatigue crack propagation behaviors. The disordered orientation of the lath-like α-grains enhances the fatigue crack initiation resistance of UAM-assisted vibration SLM components. However, for UAM-assisted additive manufacturing of titanium alloys, most research focuses on arc additive manufacturing and laser wire fabrication, where the molten pool behavior differs significantly from SLM. Research on UAM-assisted SLM for titanium alloy fabrication is scarce and remains in the development stage.

[0007] In summary, combining the addition of TiO2 particles with SLM technology can effectively improve the strength of Ti-O alloys. However, defects such as circular pores and irregular incomplete pores formed by SLM technology negatively impact the plasticity of Ti-O alloys. Furthermore, the technology for preparing Ti-O alloys using ultrasound-assisted SLM is still under development. Based on these shortcomings in SLM technology for preparing Ti-O alloys, there is an urgent need to develop a device and method for ultrasonic vibration-assisted SLM forming. Summary of the Invention

[0008] The purpose of this invention is to provide an apparatus and method for ultrasonic-assisted SLM forming of Ti-O alloys. This apparatus and method help to change the microstructure of Ti-O alloys, thereby improving the forming quality and comprehensive mechanical properties of SLM-formed Ti-O alloys.

[0009] The technical solution of the present invention is as follows: an apparatus for ultrasonic-assisted SLM forming of Ti-O alloy, comprising a sealed chamber for filling with high-purity argon gas, a base plate disposed in the sealed chamber, an ultrasonic vibration integrated platform connected to an ultrasonic generator mounted on the base plate, a substrate mounted on the upper side of the ultrasonic vibration integrated platform for laying powder, a scraper powder laying mechanism disposed on the upper side of the substrate, and a laser beam generating device for acting on the powder disposed above the substrate.

[0010] Furthermore, an argon gas inlet pipe is provided on one side of the sealed cavity, and the input end of the argon gas inlet pipe is connected to a high-purity argon gas source.

[0011] Furthermore, the ultrasonic vibration integrated platform is fixed on the base, and the two sides of the substrate are connected to the base via vertical sections.

[0012] Furthermore, a layer of flexible foam cotton is filled between the bottom surface of the substrate and the ultrasonic vibration integrated platform.

[0013] Furthermore, the scraper powder spreading mechanism includes a scraper that moves laterally driven by a first drive mechanism, and is provided with a second drive mechanism that drives the first drive mechanism to move up and down.

[0014] Furthermore, the laser beam generating device includes a fiber laser, which is connected via a flexible optical fiber to a galvanometer-lens system that acts downwards on the upper surface of the substrate.

[0015] A method for ultrasonic vibration-assisted SLM forming of Ti-O alloy, employing an ultrasonic-assisted SLM forming device for Ti-O alloy, includes the following steps:

[0016] (1) CP-Ti powder and TiO2 powder are mixed in a certain proportion and mixed using a powder mixer to form TiO2 / Ti mixed powder;

[0017] (2) High-purity argon gas is introduced into the sealed chamber, and then TiO2 / Ti mixed powder is spread on the substrate by a scraper powder spreading mechanism;

[0018] (3) Turn on the ultrasonic generator and transmit the ultrasonic vibration to the spread TiO2 / Ti mixed powder on the substrate through the ultrasonic vibration integrated platform;

[0019] (4) Turn on the fiber laser and the emitted laser beam is transmitted through the flexible optical fiber to the galvanometer-lens system and finally acts on the spread TiO2 / Ti mixed powder. At the same time as turning on the fiber laser, turn on the ultrasonic generator and use its acoustic cavitation effect to change the flow and solidification behavior of the molten pool, thereby changing the microstructure of the Ti-O alloy.

[0020] Furthermore, the powder mixer is a planetary ball mill.

[0021] Furthermore, the mixing time of the powder mixer is 110~130min, and the rotation speed is 180~220rpm / min.

[0022] Furthermore, during the TiO2 / Ti mixed powder spreading stage, the ultrasonic power is 50~70W and the frequency is 25~35kHz; during the SLM forming Ti-O alloy stage, the ultrasonic power is 110~130W and the frequency is 25~35kHz.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) Excellent performance: By using ultrasonic vibration to assist SLM forming of Ti-O alloy, the ultrasonic cavitation effect is utilized to introduce ultrasonic-assisted vibration with different process parameters in the powder laying stage and SLM additive process, thereby changing the flow and solidification behavior of the molten pool, thus changing the microstructure of Ti-O alloy, and improving the forming quality and comprehensive mechanical properties of SLM formed Ti-O alloy.

[0025] (2) The Ti-O alloy prepared by this method has excellent biocompatibility and mechanical properties, which meets the safety requirements of implants during human service.

[0026] (3) The device for ultrasonic vibration-assisted SLM forming of Ti-O alloy integrates the ultrasonic vibration integrated platform and the substrate for spreading powder together. The device has a simple structure and is easy to operate. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the device for ultrasonic vibration-assisted SLM forming of Ti-O alloy according to the present invention;

[0028] Figure 2 The working process of the device for ultrasonic-assisted SLM forming of Ti-O alloy in this invention is as follows;

[0029] Figure 3 The elemental content of the Ti-O alloy of this invention;

[0030] Figure 4 A micrograph of the TiO2 / Ti mixed powder after ball milling according to the present invention;

[0031] Figure 5 This is a scanning electron microscope image of the ultrasonically assisted forming Ti-O alloy of the present invention after electrolytic polishing;

[0032] Figure 6 The image shows the metallographic microstructure of the ultrasonically assisted forming Ti-O alloy of the present invention.

[0033] Figure 7 The stress-strain curve of the ultrasonically assisted forming Ti-O alloy of the present invention is shown below.

[0034] In the figure: 1-Sealed chamber 2-Base 3-Ultrasonic vibration integrated platform 4-Substrate 5-Scraper powder spreading mechanism 6-Galvanometer-lens system 7-Fiber laser 8-Formed Ti-O sample 9-Ultrasonic generator 10-Argon gas inlet pipe 11-High-purity argon gas source. Detailed Implementation

[0035] To make the above features and advantages of the present invention more readily understood, specific embodiments are described below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0036] refer to Figures 1 to 7

[0037] An apparatus for ultrasonic-assisted SLM forming of Ti-O alloy includes a sealed chamber 1 for filling with high-purity argon gas and capable of being sealed. A base 2 is disposed within the sealed chamber. An ultrasonic vibration integrated platform 3 connected to an ultrasonic generator 9 is mounted on the base. A substrate 4, located above the ultrasonic vibration integrated platform and used for powder spreading, is mounted on the base. A scraper powder spreading mechanism 5 is disposed on the upper side of the substrate. A laser beam generating device for acting on the powder is disposed above the substrate. Figure 1 As shown.

[0038] In this embodiment, an argon gas inlet pipe 10 is provided on one side of the sealed cavity. The input end of the argon gas inlet pipe is connected to a high-purity argon gas source 11, thereby controlling the flow of high-purity argon gas.

[0039] In this embodiment, the sealed chamber is provided with a discharge window that can be sealed so that the sealed chamber can be closed after the powder is placed into the substrate.

[0040] In this embodiment, the ultrasonic vibration integrated platform is fixed on the base, and the two sides of the substrate are connected to the base via vertical sections.

[0041] In this embodiment, a layer of flexible foam cotton is filled between the bottom surface of the substrate and the ultrasonic vibration integration platform to prevent the attenuation of ultrasonic vibration.

[0042] In this embodiment, the scraper powder spreading mechanism includes a scraper that moves laterally driven by a first driving mechanism, and a second driving mechanism that drives the first driving mechanism to move up and down. This drives the scraper to move laterally and adjust its height. For example, the first driving mechanism can be a laterally positioned slide cylinder, with the scraper mounted on the slide cylinder and extending forward to the upper side of the substrate. The second driving mechanism can be a vertically positioned electric cylinder, with its extension rod connected to the bottom surface of the slide cylinder, thereby driving the slide cylinder to adjust the scraper's height.

[0043] In this embodiment, the laser beam generating device includes a fiber laser 7, which is connected to a galvanometer-lens system 6 that acts downward on the upper surface of the substrate via a flexible optical fiber, so that the laser beam emitted by the fiber laser 7 is transmitted from the flexible optical fiber to the galvanometer-lens system 6 and finally acts on the spread powder.

[0044] See Figure 2 A method for ultrasonic vibration-assisted SLM forming of Ti-O alloy, employing an ultrasonic-assisted SLM forming device for Ti-O alloy, includes the following steps:

[0045] (1) CP-Ti powder and TiO2 powder are mixed in a certain proportion and then mixed using a powder mixer to form a uniformly mixed TiO2 / Ti powder; such as Figure 3 and Figure 4 As shown;

[0046] (2) High-purity argon gas is introduced into the sealed chamber, and then TiO2 / Ti mixed powder is spread on the substrate 4 by the scraper powder spreading mechanism 5;

[0047] (3) Turn on the ultrasonic generator 9 and transmit the ultrasonic vibration to the TiO2 / Ti mixed powder on the substrate 4 through the ultrasonic vibration integrated platform 3. By introducing ultrasonic-assisted vibration with a certain power and frequency, the spreading quality of the powder is improved.

[0048] (4) SLM forming process of Ti-O alloy: Turn on the fiber laser 7. The laser beam emitted by the fiber laser is transmitted to the galvanometer-lens system 6 through the flexible optical fiber and finally acts on the spread TiO2 / Ti mixed powder. At the same time as turning on the fiber laser, turn on the ultrasonic generator 9. Utilize its acoustic cavitation effect to change the flow and solidification behavior of the molten pool, change the microstructure of the Ti-O alloy, and thus obtain a Ti-O alloy with finer microstructure and better comprehensive mechanical properties.

[0049] In this embodiment, the oxygen content of the Ti-O material is designed to be 0.10~0.30 wt.%.

[0050] In this embodiment, the powder mixer is a planetary ball mill, which directly obtains a mixed powder with a uniform oxygen content distribution by using a planetary ball mill mixing method.

[0051] In this embodiment, the mixing time of the powder mixer is 110~130 min, and the rotation speed is 180~220 rpm / min. Specifically, for example, the mixing time is 110 min, and the rotation speed is 180 rpm / min; or the mixing time is 120 min, and the rotation speed is 200 rpm / min; or the mixing time is 130 min, and the rotation speed is 220 rpm / min.

[0052] In this embodiment, during the TiO2 / Ti mixed powder spreading stage, the ultrasonic power is 50~70W and the frequency is 25~35kHz, thereby improving the powder spreading quality. During the SLM forming stage of the Ti-O alloy, the ultrasonic power is 110~130W and the frequency is 25~35kHz, thereby changing the microstructure of the Ti-O alloy.

[0053] For example, in the TiO2 / Ti mixed powder spreading stage, the ultrasonic power is 50W and the frequency is 25kHz; or the ultrasonic power is 70W and the frequency is 35kHz. In the SLM forming stage of Ti-O alloy, the ultrasonic power is 110W and the frequency is 25kHz; or the ultrasonic power is 130W and the frequency is 35kHz.

[0054] Specifically, in a preferred embodiment, during the TiO2 / Ti mixed powder spreading stage, the ultrasonic power is 60W and the frequency is 28kHz; during the SLM forming stage of the Ti-O alloy, the ultrasonic power is 120W and the frequency is 28kHz. The surface quality of the Ti-O alloy prepared by ultrasonic-assisted SLM is as follows: Figure 5 As shown, the microstructure is as follows Figure 6 The stress-strain curve is as follows Figure 7 As shown.

[0055] The above description is only a preferred embodiment of the present invention. For those skilled in the art, designing different forms of ultrasonic-assisted SLM forming devices and working methods for Ti-O alloys based on the teachings of the present invention does not require creative labor. All equivalent changes, modifications, substitutions and variations made in accordance with the scope of the patent application of the present invention without departing from the principles and spirit of the present invention shall be covered by the present invention.

Claims

1. A method for ultrasonic vibration-assisted SLM forming of Ti-O alloy, comprising an apparatus for ultrasonic-assisted SLM forming of Ti-O alloy, characterized in that, The apparatus for ultrasonic-assisted SLM forming of Ti-O alloy includes a sealed chamber for filling with high-purity argon gas, a base platform disposed within the sealed chamber, an ultrasonic vibration integrated platform connected to an ultrasonic generator mounted on the base platform, the ultrasonic vibration integrated platform being fixed on the base platform, a substrate for laying powder mounted on the base platform located above the ultrasonic vibration integrated platform, the two sides of the substrate being connected to the base platform via vertical sections; a layer of flexible foam cotton is filled between the bottom surface of the substrate and the ultrasonic vibration integrated platform; a scraper powder laying mechanism is disposed on the upper side of the substrate, and a laser beam generating device for acting on the powder is disposed above the substrate; The laser beam generating device includes a fiber laser, which is connected via a flexible optical fiber to a galvanometer-lens system that acts downwards on the upper surface of the substrate; the operating method includes the following steps: (1) CP-Ti powder and TiO2 powder are mixed in a certain proportion and mixed using a powder mixer to form TiO2 / Ti mixed powder; the powder mixer is a planetary ball mill; the mixing time of the powder mixer is 110~130min and the rotation speed is 180~220rpm / min; (2) High-purity argon gas is introduced into the sealed chamber, and then TiO2 / Ti mixed powder is spread on the substrate by a scraper powder spreading mechanism; (3) Turn on the ultrasonic generator and transmit the ultrasonic vibration to the TiO2 / Ti mixed powder on the substrate through the ultrasonic vibration integrated platform; during the TiO2 / Ti mixed powder spreading stage, the ultrasonic power is 50~70W and the frequency is 25~35Khz to improve the powder spreading quality of the scraper mechanism; during the SLM forming Ti-O alloy stage, the ultrasonic power is 110~130W and the frequency is 25~35Khz to improve the microstructure and mechanical properties of the SLM forming Ti-O alloy. (4) Turn on the fiber laser and the emitted laser beam is transmitted through the flexible optical fiber to the galvanometer-lens system and finally acts on the spread TiO2 / Ti mixed powder. At the same time as turning on the fiber laser, turn on the ultrasonic generator and use its acoustic cavitation effect to change the flow and solidification behavior of the molten pool, thereby changing the microstructure of the Ti-O alloy.

2. The working method for ultrasonic vibration-assisted SLM forming of Ti-O alloy according to claim 1, characterized in that, An argon gas inlet pipe is provided on one side of the sealed cavity, and the input end of the argon gas inlet pipe is connected to a high-purity argon gas source.

3. The working method for ultrasonic vibration-assisted SLM forming of Ti-O alloy according to claim 1 or 2, characterized in that, The scraper powder spreading mechanism includes a scraper that moves laterally driven by a first drive mechanism, and a second drive mechanism that drives the first drive mechanism to move up and down.

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