阅读说明：本技术 一种利用超声冲击调控激光增材制造钛材料组织与性能的方法 (Method for manufacturing titanium material structure and performance by using ultrasonic impact to regulate and control laser material increase ) 是由 佟运祥 王福斌 王建东 刘宇珂 许德 姜风春 于 2021-07-07 设计创作，主要内容包括：本发明提供一种利用超声冲击调控激光增材制造钛材料组织与性能的方法：(一)利用激光增材制造技术制备微观组织为等轴晶的钛材料,激光功率为800～3000W,扫描速度100～500mm/min,送粉率7～28g/min。(二)根据零件设计需要,在送粉器关闭后,利用超声冲击设备对零件进行处理,超声冲击头功率300～1000W,冲击头速度100～500mm/min,工作频率不低于20KHz；(三)在处理后的零件上继续利用激光增材制造技术沉积钛材料；(四)根据零件设计需要,重复步骤(二)和(三)；(五)待零件冷却至室温后取出。本发明具有工艺简单、实施快速、可应用于大型工件处理,适用范围广等优点。(The invention provides a method for manufacturing titanium material tissue and performance by using ultrasonic impact to regulate and control laser material increase, which comprises the following steps: firstly, a titanium material with an isometric crystal microstructure is prepared by using a laser additive manufacturing technology, wherein the laser power is 800-3000W, the scanning speed is 100-500 mm/min, and the powder feeding rate is 7-28 g/min. Secondly, processing the parts by using ultrasonic impact equipment after the powder feeder is closed according to the design requirements of the parts, wherein the power of an ultrasonic impact head is 300-1000W, the speed of the impact head is 100-500 mm/min, and the working frequency is not lower than 20 KHz; thirdly, continuously depositing a titanium material on the processed part by using a laser additive manufacturing technology; fourthly, repeating the second step and the third step according to the design requirement of the part; and (V) taking out the part after the part is cooled to room temperature. The invention has the advantages of simple process, quick implementation, wide application range and the like, and can be applied to the treatment of large-scale workpieces.)

1. A method for regulating and controlling the texture and the performance of a titanium material manufactured by laser material increase by utilizing ultrasonic impact is characterized by comprising the following steps of:

(1) preparing powder by adopting a plasma rotating electrode method, and ensuring certain particle size and sphericity rate of a finished product;

(2) drying the powder by a hot air circulation oven before filling, wherein the drying temperature is 80-120 ℃, and the drying time is 1-5 h; then placing the powder in a powder box, and pressurizing and feeding the powder by using argon in the working process;

(3) depositing layer by layer on a substrate fixed in an argon filling chamber, wherein the content of residual oxygen is lower than 300ppm, defining the lifting distance of a laser according to the single-layer additive manufacturing deposition height, ensuring that the relative position of a laser focus point and each layer is unchanged, opening a powder feeder to operate for 5-10 s under the condition that the laser is not opened after the laser moves to a starting position and is lifted for a certain distance, ensuring that the powder feeding is uniform, starting each layer at the same laser scanning speed at the same starting position, repeating the same path, closing the powder feeder after the deposition is finished, selecting the powder feeding speed to be 800-3000 w according to different material laser powers, the scanning speed to be 100-500 mm/min, and the powder feeding rate to be changed within the range of 7-28 g/min, so as to obtain an isometric crystal structure;

(4) after the powder feeder stops working, moving an ultrasonic impact head to the position where a laser head starts according to the design requirement of parts, and impacting, wherein the moving path of the ultrasonic impact head is consistent with the laser scanning path, the power of the ultrasonic impact head is 300-1000W, the speed of the impact head is 100-500 mm/min, and the working frequency is not lower than 20 KHz;

(5) continuously depositing the titanium material by using the parameters in the step (3) on the surface of the part subjected to the ultrasonic impact treatment, wherein the microstructure of the newly deposited titanium material is columnar crystal;

(6) repeating the step 4-5;

(7) and taking out the part after the part is cooled to room temperature, thus obtaining the part with the mixed microstructure of the equiaxed crystals and the columnar crystals.

2. The method for regulating and controlling the texture and the performance of the titanium material by the laser additive manufacturing method through the ultrasonic impact as claimed in claim 1, wherein the alloy additive manufacturing technology comprises a laser melting deposition technology, a laser fuse technology and a combination of the additive manufacturing technologies.

3. The method for regulating and controlling the texture and the performance of the laser additive manufactured titanium material by utilizing the ultrasonic impact as claimed in claim 1, wherein the ultrasonic impact device is a high-frequency vibration impact device, and different treatment effects can be obtained by adjusting the scanning speed and the vibration power of an impact head.

4. The method for regulating and controlling the structure and the performance of the titanium material additive manufactured by the laser through ultrasonic impact according to claim 1, wherein the action direction of the ultrasonic impact is consistent with the thermal gradient direction of the part.

5. The method for regulating and controlling the texture and the performance of the laser additive manufactured titanium material by utilizing the ultrasonic impact as claimed in claim 1, wherein the process is suitable for titanium alloy and titanium-based composite materials.

6. The method for regulating and controlling the texture and the performance of the laser additive manufactured titanium material by utilizing the ultrasonic impact as claimed in claim 1, wherein the process is suitable for the laser additive manufactured aluminum alloy and the composite material thereof, stainless steel, Ni-based high-temperature alloy and the composite material thereof.

Technical Field

The invention belongs to the field of laser additive manufacturing material forming processing, and particularly relates to a method for regulating and controlling microstructure and performance of a titanium material by laser additive manufacturing through ultrasonic impact.

Background

The titanium alloy and titanium-based composite material has the characteristics of high specific strength, excellent corrosion resistance and heat resistance and the like, and is usually used for preparing important force-bearing components in engineering application and implanting instruments in biomedicine. The complex application requirements set individual requirements on the mechanical properties of the titanium material.

The laser additive manufacturing technology has unique advantages in the aspects of processing parts with complex shapes and reducing material waste, and is particularly suitable for forming titanium material parts which are difficult to process. Due to the characteristic of high heating and condensing speed in the forming process, the microstructure of the titanium material manufactured by laser additive manufacturing is generally composed of epitaxially grown beta columnar crystals. By regulating and controlling the laser additive manufacturing process, the microstructure of the isometric crystal can be obtained in the titanium material. At present, the microstructure of the titanium material is regulated and controlled mainly by regulating and controlling laser additive manufacturing process parameters of the titanium material or introducing post-treatment, so that the personalized mechanical property is realized. Meanwhile, the high performance and complexity of the part design also put forward different differentiation requirements on the microstructure and the mechanical property of different positions of the part, which puts forward higher requirements on the additive manufacturing process.

The patent with application number 201811318378.0 discloses that the titanium alloy equiaxed crystal structure is manufactured by regulating and increasing materials through induction heating micro-forging, and a microstructure with equiaxed crystals at the outer layer and columnar crystals at the middle part is obtained. However, the process requires induction heating, and the equipment and the process are complex, so that the processing of parts with complex shapes and large overall dimensions is difficult to meet. The patent with application number 202010282733.4 utilizes ultrasonic impact to convert columnar crystals in titanium alloy prepared by laser fuse additive manufacturing into isometric crystals, and the transformation from isometric crystals to columnar crystals cannot be realized. The patent with application number 202011368033.3 obtains a microstructure with equiaxial crystals and columnar crystals alternately distributed by regulating and controlling laser additive manufacturing process parameters and subsequent heat treatment process parameters, but the heat treatment steps are more and the process is complex.

In summary, although there are many processes capable of obtaining a mixed structure of equiaxial crystals and columnar crystals, the processes are complicated, or the transformation from equiaxial crystals to columnar crystals cannot be realized, or the use requirement of microstructure position differentiation cannot be met.

Disclosure of Invention

The invention provides a method for obtaining isometric crystals and columnar crystals by using a coupling process of ultrasonic impact and laser additive manufacturing, aiming at the defect of complex process for obtaining a laser additive manufacturing titanium material with a mixed structure of the isometric crystals and the columnar crystals. By adopting the technical scheme of the invention, free design of equiaxial crystal structures and columnar crystal structures can be realized under proper process parameters, and individuation and differentiation of mechanical properties of parts are realized.

The technical scheme of the invention is as follows:

(1) preparing powder by adopting a plasma rotating electrode method, and ensuring certain particle size and sphericity rate of a finished product;

(2) drying the powder by a hot air circulation oven before filling, wherein the drying temperature is 80-120 ℃, and the drying time is 1-5 h; then placing the powder in a powder box, and pressurizing and feeding the powder by using argon in the working process;

(3) depositing layer by layer on a substrate fixed in an argon filling cabin, wherein the content of residual oxygen is less than 300 ppm. According to the single-layer additive manufacturing deposition height, the lifting distance of the laser is defined, and the relative position of the laser focus point and each layer is guaranteed to be unchanged. After the laser moves to the starting position and is lifted for a certain distance, the powder feeder is firstly opened to operate for 5-10 s under the condition that the laser is not started, and the powder feeding uniformity is ensured. Each layer starts at the same starting position and at the same laser scanning speed and the same path is repeated, and the powder feeder is closed after deposition is completed. The laser power of different materials is selected to be 800-3000 w, the scanning speed is 100-500 mm/min, and the powder feeding rate is changed within the range of 7-28 g/min, so that the equiaxial crystal structure is obtained.

(4) And stopping the powder feeder. According to the design requirement of parts, the ultrasonic impact head moves to the position where the laser head starts to impact. The moving path of the ultrasonic impact head is consistent with the laser scanning path. The power of the ultrasonic impact head is 300-1000W, the speed of the impact head is 100-500 mm/min, and the working frequency is not lower than 20 KHz.

(5) And (4) continuing to deposit the titanium material by using the parameters in the step (3) on the surface of the part subjected to the ultrasonic impact treatment, wherein the microstructure of the newly deposited titanium material is columnar crystal.

(6) Repeating the step 4-5;

(7) and taking out the part after the part is cooled to room temperature, thus obtaining the part with the mixed microstructure of the equiaxed crystals and the columnar crystals.

Further, additive manufacturing techniques for the alloy include laser fuse deposition techniques, laser fuse techniques, and combinations thereof.

Furthermore, the ultrasonic impact equipment is high-frequency vibration impact equipment, and different treatment effects can be obtained by adjusting the scanning speed and the vibration power of the impact head.

Further, the ultrasonic impact action direction is consistent with the thermal gradient direction of the part.

Further, the above process is applicable not only to titanium alloys but also to titanium-based composites.

Furthermore, the process is suitable for laser additive manufacturing of aluminum alloy and composite materials thereof, stainless steel, Ni-based high-temperature alloy and composite materials thereof and the like.

Compared with the prior art, the invention has the beneficial effects that:

the ultrasonic impact has a remarkable regulation and control effect on regulating and controlling the microstructure of the titanium material manufactured by the laser additive. The stress state of the surface of the material can be changed and the surface grain size can be refined under the action of ultrasonic impact and the surface of the titanium material, so that the nucleation and growth behaviors of the titanium material grains continuously deposited on the surface are regulated and controlled, the grains grow again in a columnar crystal form along the direction of thermal gradient, and finally, a mixed structure of isometric crystals and columnar crystals is obtained. Meanwhile, the invention can conveniently regulate and control the proportion of the columnar crystal and the isometric crystal, regulate and control the forming position of the columnar crystal in the part and optimize the mechanical properties such as the strength, the elongation and the like of the material by regulating the technological parameters (such as time) for applying the ultrasonic impact, and can meet the individualized use requirement of the complicated working conditions on the performance of the part. Compared with other processing modes, the method for coupling the laser additive manufacturing process and the ultrasonic impact process does not need subsequent working procedures such as heat treatment and the like, and is simple and flexible in process and easy to popularize and use.

Drawings

FIG. 1 is a microstructure of a laser fusion deposited Ti6Al4V alloy;

FIG. 2 is a microstructure of an ultrasonic impact and laser fused deposition coupled Ti6Al4V alloy;

FIG. 3 shows the microhardness distribution of Ti6Al4V alloy processed by ultrasonic impact and laser melting deposition in the deposition direction.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

A regulating method for manufacturing a microstructure of a titanium material by laser additive manufacturing relates to a method for regulating and controlling the microstructure of the material by ultrasonic impact, and comprises the following steps: firstly, a titanium material with an isometric crystal microstructure is prepared by using a laser additive manufacturing technology, wherein the laser power is 800-3000W, the scanning speed is 100-500 mm/min, and the powder feeding rate is 7-28 g/min. Secondly, processing the parts by using ultrasonic impact equipment after the powder feeder is closed according to the design requirements of the parts, wherein the power of an ultrasonic impact head is 300-1000W, the speed of the impact head is 100-500 mm/min, and the working frequency is not lower than 20 KHz; thirdly, continuously depositing a titanium material on the processed part by using a laser additive manufacturing technology; fourthly, repeating the second step and the third step according to the design requirement of the part; and (V) taking out the part after the part is cooled to room temperature. The method is characterized in that the laser additive manufacturing technology in the first step comprises the technologies of laser melting deposition, laser fuse deposition and the like, the microstructure of the material obtained in the first step is isometric crystal, the part is subjected to ultrasonic impact treatment in the second step, and the microstructure of the material continuously deposited on the surface of the treated part is columnar crystal.

The first embodiment is as follows:

(1) preparing Ti6Al4V alloy by adopting a plasma rotating electrode method, wherein the particle size of the powder is 45-100 mu m, and the sphericity ratio is 99.6%;

(2) before powder is filled, drying the powder for 2 hours at 80 ℃, then placing the powder in a powder box, and providing 15MPa argon gas for powder feeding in the working process;

(3) and (3) depositing the Ti6Al4V substrate fixed in the argon-filled cabin layer by layer. According to the deposition height of additive manufacturing, the lifting distance of the laser is defined to be 12-15 mm, and the relative position of a laser focus point and each layer is guaranteed to be unchanged. After the laser moves to the starting position and is lifted for a certain distance, the powder feeder is firstly opened to operate for 5-10 s under the condition that the laser is not started, and the powder feeding uniformity is ensured. Each layer starts at the same starting position and at the same laser scanning speed and the same path is repeated, and the powder feeder is closed after deposition is completed. The laser power of different materials is selected to be 1500w, the scanning speed is 400mm/min, the sending rate is changed within the range of 15g/min, and the isometric crystal structure of the deposition state is obtained.

(4) After the single-pass deposition is finished, the powder feeder stops working. The ultrasonic impact head moves to the position where the laser head starts, and the moving path is the same as the laser scanning path. The power of the impact head is 600w, and the moving speed of the impact head is 500 mm/min.

(5) Repeating the steps 3-4 when each layer is deposited in the additive manufacturing process according to the design requirement, and co-depositing 20 layers;

(6) and taking out the additive manufacturing deposition piece after the additive manufacturing deposition piece is cooled to room temperature.

FIG. 1 shows the optical microstructure of Ti6Al4V alloy deposited by laser melting without ultrasonic impact, and the microstructure of the alloy is equiaxial crystal with the grain size of about 200-300 μm. FIG. 2 shows an optical microstructure of Ti6Al4V alloy prepared by coupling ultrasonic impact and laser melting deposition, wherein FIG. 2(a) shows an equiaxial crystal structure, FIG. 2(b) shows a columnar crystal structure, and the microstructure of the alloy is composed of equiaxial crystals with a grain size of about 250-350 μm and columnar crystals with a grain width of about 300-400 μm. FIG. 3 is a micro-hardness distribution of Ti6Al4V alloy prepared by coupling ultrasonic impact and laser melting deposition along the deposition direction, and it can be seen that the hardness of the alloy is further improved by ultrasonic impact compared with that of the alloy without ultrasonic impact; meanwhile, the microhardness distribution is identical with the shape and size distribution of the crystal grains. Compared with other processing modes, the ultrasonic impact can conveniently adjust the proportion of columnar crystals and isometric crystals, eliminate the defects of air holes, poor fusion and the like possibly formed in the laser deposition process and adjust the surface stress state into the compressive stress beneficial to the mechanical property.

The second embodiment is as follows:

the difference between this embodiment and the first embodiment is that the alloy in step (1) is prepared by using a laser fuse technology.

The third concrete implementation mode:

the difference between this embodiment and the first embodiment is that the material in step (1) is a titanium-based composite material.

The fourth concrete implementation mode:

the present embodiment is different from the first embodiment in that the material in the step (1) is an aluminum alloy and a composite material thereof.

The fifth concrete implementation mode:

the present embodiment is different from the first embodiment in that the material used in step (1) is stainless steel.

The sixth specific implementation mode:

the present embodiment is different from the first embodiment in that the material in the step (1) is a Ni-based superalloy and a composite material thereof.

In summary, the following steps: a method for regulating and controlling the texture and performance of a titanium material manufactured by laser additive by combining ultrasonic impact and a laser additive manufacturing process solves the problem of complex process in the prior art, and can realize the customization of microstructure according to the use requirement of parts. The method comprises the following steps: firstly, a titanium material with an isometric crystal microstructure is prepared by using a laser additive manufacturing technology, wherein the laser power is 800-3000W, the scanning speed is 100-500 mm/min, and the powder feeding rate is 7-28 g/min. Secondly, processing the parts by using ultrasonic impact equipment after the powder feeder is closed according to the design requirements of the parts, wherein the power of an ultrasonic impact head is 300-1000W, the speed of the impact head is 100-500 mm/min, and the working frequency is not lower than 20 KHz; thirdly, continuously depositing a titanium material on the processed part by using a laser additive manufacturing technology; fourthly, repeating the second step and the third step according to the design requirement of the part; and (V) taking out the part after the part is cooled to room temperature. The invention has the advantages of simple process, quick implementation, wide application range and the like, can be applied to large-scale workpiece treatment, and can be applied to the additive manufacturing of parts prepared from titanium alloy, stainless steel, aluminum alloy, high-temperature alloy and composite materials thereof.