CN105127666A - Method for ultrafine modification of surface of TC4 titanium alloy - Google Patents

Abstract

The invention provides a method for superfine modification of the surface of TC4 titanium alloy, which comprises the following steps: S1: selecting a defect-free TC4 titanium alloy sample, grinding and straightening; Grooves are prefabricated on the surface to add silver particles; S3: Fix the TC4 titanium alloy after adding silver particles on the workbench of the friction stir welding equipment, and process it under the protection of argon gas. Compared with the prior art, the present invention has the following beneficial effects: the method of the present invention is carried out on the surface of TC4 titanium alloy, which overcomes the defect that the surface of the material is difficult to deform, and can significantly refine the crystal grains after adding nano-scale silver particles , improve the biological activity of the surface of the material, and avoid the occurrence of tissue infection after implantation.

Description

A superfine modification method for the surface of TC4 titanium alloy

technical field

The present invention relates to a method for surface modification of TC4 titanium alloy with nano-reinforced silver particles used in the field of surgical implantation, specifically adopting friction stir surface treatment technology to carry out strong plastic surface modification on Ti-6Al-4V, That is, the ultra-fine modification method of the surface of TC4 titanium alloy is prepared by adding nano-scale silver particles to prepare nano-composite biomedical titanium alloy.

Background technique

In the early 1950s, in the United Kingdom and the United States, pure titanium was first used to manufacture biomedical materials such as bone plates, hip joints, intramedullary nails and screws. However, it has been found clinically that the strength and stiffness of hip joints and intramedullary nails made of pure titanium are obviously insufficient. Since then, biomedical titanium alloy materials have been greatly developed. At present, titanium alloy is the most attractive biomedical metallurgy material. However, the application of titanium alloys in biomedicine not only requires its mechanical properties, but also has more specific requirements for biocompatibility and corrosion resistance with the human environment on the basis of ensuring biological safety. requirements, and are quite different in different applications.

The composition of titanium alloy TC4 material is Ti-6Al-4V, which belongs to α+β type titanium alloy and has good comprehensive mechanical and mechanical properties. Ti-6Al-4V alloy has been widely used in many industrial fields due to its high specific strength, low density, biocompatibility and other excellent properties. However, the surface wearability of Ti-6Al-4V alloy is poor, which affects the service life of the product in terms of mechanical friction, and limits its application in biomedical applications such as hip implants [3]. The research on the surface modification of Ti-6Al-4V alloy can improve the performance of its surface. In recent years, friction stir processing technology has developed rapidly in China. It is a new type of material surface processing technology and has broad application prospects. In China, research on friction stir processing technology mainly focuses on light alloys such as aluminum and magnesium, which can improve the hardness and wear resistance of the alloy surface and the overall strength, plasticity and toughness of the material. However, domestic research on friction stir processing technology in biomedical metals is still in its infancy. Friction stir processing technology can modify the surface of TC4 titanium alloy to make it have better mechanical properties and surface properties, and improve biocompatibility to a certain extent. However, implant-related infection inevitably occurs in postoperative syndrome. It has been reported in the literature that the annual incidence of orthopedic implant-related infection in the United States reaches 4.3%, which has become a major problem that plagues orthopedic implant surgery.

Contents of the invention

In view of the defects in the prior art, the purpose of the present invention is to provide a method for ultra-fine modification of the surface of TC4 titanium alloy, which applies friction stir surface treatment (FSP) to the prior art and application requirements In TC4 titanium alloy, the material surface grain size and roughness can be effectively controlled. At the same time, the wear resistance and biological activity of the material surface can be improved by adding nano-scale silver particles, and bacterial infection after implantation can be avoided. It can be widely used in surgery implant field.

The present invention is achieved through the following technical solutions:

The invention provides a method for superfine modification of the surface of TC4 titanium alloy, which comprises the following steps:

S1: Select a defect-free TC4 titanium alloy sample for grinding and straightening;

S2: prefabricating grooves on the surface of the TC4 titanium alloy so as to add silver particles;

S3: Fill and scatter silver particles in the prefabricated grooves, and then process them on the workbench of the friction stir welding equipment under the protection of argon gas.

As a preferred solution, the smelting method of the TC4 titanium alloy is smelting in a vacuum consumable furnace.

As a preferred version, the operation of the vacuum consumable furnace smelting is:

After the Ti-6Al-4V alloy is smelted three times, the material is forged above the β phase transformation point of the Ti-6Al-4V alloy, and then the temperature-controlled forging is carried out in the α+β phase region of the Ti-6Al-4V alloy , and finally hot rolling;

Wherein, the blank forging temperature is 1010-1050°C, and the temperature-controlled forging and hot rolling temperature is 920-950°C.

As a preferred solution, the depth of the groove is 0.5-2 mm.

As a preferred solution, the straightening adopts a four-roll cold straightening machine.

As a preferred solution, in step S3, the processing speed of the stirring head of the friction stir welding equipment is 50 mm/min, and the rotating speed of the stirring head is 225-375 r/min.

As a preferred solution, the average particle diameter of the silver particles is 50nm.

Studies have shown that compared with other metal ions, Ag ⁺ has a strong bactericidal ability and can well avoid infection after orthopedic implants. Therefore, the introduction of nano-scale Ag particles into the strong plastic deformation of TC4 titanium alloy makes the grains of the material finer, improves the mechanical properties, and greatly avoids the problem of infection after implantation.

Compared with the prior art, the present invention has the following beneficial effects:

The method of the present invention is carried out on the surface of TC4 titanium alloy, which overcomes the defect that the surface of the material is difficult to deform. After adding nano-scale silver particles, the crystal grains can be significantly refined, the biological activity of the material surface can be improved, and tissue infection after implantation can be avoided. happened.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the distribution (processing speed 50mm/min, stirring head rotation speed 375r/min) of the Ag particle layer on the TC4 surface after 1 pass stirring;

Fig. 2 is the product of embodiment 1 and the nano-indentation loading curve of control sample;

Figure 3 is a SEM image of the corresponding indentation in Figure 2;

Fig. 4 is the test result figure after inoculating Staphylococcus aureus respectively in product and control sample;

Figure 5 is a diagram of the antibacterial rate of silver-added samples.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example 1

Using friction stir surface treatment to modify the surface of TC4 titanium alloy, the specific steps are as follows:

(a) Material preparation: use intermediate alloy additives to weigh according to the composition ratio, use vacuum self-consumable melting technology to repeatedly melt Ti-6Al-4V (wt%) titanium alloy three times, and melt an ingot with a diameter of 80-120mm. The material is forged at 1050°C and 950°C respectively, and forged into a billet with a thickness of 30-50mm. After grinding the surface defects of the material, the material is hot-rolled at 950°C. The deformation of each pass is controlled at 5-8%. To a thickness of about 4 ~ 6mm;

(b) Material flaw detection and surface treatment: grind the surface of TC4 titanium alloy with a thickness of about 4-6 mm after rolling to remove scale, use a four-roll cold leveler to straighten the material, and use ultrasonic flaw detection to confirm that the material has no pores, etc. Defects, use a grinder to polish the surface of the material to a smooth state;

(c), design surface grooves: prefabricated grooves with a depth of 0.5mm on the surface of TC4 titanium alloy to add silver particles;

(d), install and process the sample: fix the sample fixture on the workbench of the friction stir welding equipment, and set the processing parameters; design the process parameters of the friction stir processing: processing speed 50 ~ 100mm/min, The rotation speed of the stirring head is 225~375r/min, and the depth of the shaft shoulder pressed into the surface of the workpiece is controlled to be 0.3~0.5mm during the processing;

(e), material surface treatment: carry out surface friction stir treatment surface modification to the TC4 titanium alloy that confirms to be defect-free in step (d); Processing technology is as shown in step (d), protect with argon gas during processing, process 1 passes.

The indentation performance of the TC4 titanium alloy after the surface modification of the present embodiment is as shown in table 1:

Table 1 Performance data of indentation

Point 1 is on the silver-containing site, and point 2 is on the silver-free site. The specific performance of the two points is shown in the table. Obviously, the hardness of point 1 is nearly 30.71% higher than that of point 2, reaching 5.31GPa, and the final depth is also shallower than point 2. From the SEM image, it can be clearly seen that nano-silver particles are evenly distributed in the indentation of point 1 and in the surrounding matrix, while the distribution of silver particles is not seen in point 2. This shows that the uniform addition of nano-silver particles to the matrix can effectively improve the hardness of the matrix. However, it can also be seen from the table that the modulus of elasticity has hardly changed, and point 1 is only 1.37% higher than point 2. This shows that although the addition of soft nano-silver particles can improve the hardness of the matrix from the aspect of lattice distortion hindering dislocation movement, it does not significantly increase the elastic modulus of the matrix, which has a certain effect on reducing the stress shielding effect of metal implants. .

The nanoindentation loading curves of the product obtained in this embodiment and the control sample are shown in FIG. 2 , and the scanning electron microscope photos corresponding to the indentation are shown in FIG. 3 .

The live/dead staining results of Staphylococcus aureus inoculated on the surface of two materials without surface modification and with surface modification for 6h and 24h are as follows: the biofilm formed by live bacteria is green, and the biofilm formed by dead bacteria and damaged It can be seen from Figure 4 that as the culture time extends from 6h to 24h, the green fluorescence intensity on the surface of TC4 (proliferation of living bacteria) increases, while the green fluorescence intensity on the surface of Ag-TC4 decreases, and the red fluorescence increases instead. . It can be seen that the silver nanoparticles have good antibacterial activity after they are introduced into the surface of TC4.

The antibacterial rate (Ra) is used to evaluate the number of live bacteria on the surface of Ag-TC4 after bacterial culture inoculation 6h and 24h

Ra(%)=(A-B)/A*100%

A represents the average number of viable bacteria on the surface of TC4, and B represents the average number of viable bacteria on the surface of Ag-TC4. It can be seen from Figure 5 that the antibacterial rate on the surface of Ag-TC4 reached over 90% no matter in 6h or 24h, and Ag-TC4 on the surface can inhibit the adhesion and proliferation of bacteria.

Example 2

Using friction stir surface treatment to modify the surface of TC4 titanium alloy, the specific steps are as follows:

Grooves with a depth of 1 mm were prefabricated on the surface of the TC4 titanium alloy to add silver particles, and the other conditions were the same as in Example 1, and deformation was carried out for one pass in an argon protective atmosphere.

Example 3

Using friction stir surface treatment to modify the surface of TC4 titanium alloy, the specific steps are as follows:

Prefabricated grooves with a depth of 1.5mm on the surface of the TC4 titanium alloy are used to add silver particles. Other conditions are the same as in Example 1, and one pass of deformation is carried out in an argon protective atmosphere; Figure 1 shows that the processing speed is 50mm/min, and the stirring head The distribution of the Ag particle layer on the surface of TC4 after stirring at a rotation speed of 375r/min for one pass.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (8)

1. a method for superfine modification of TC4 titanium alloy surface, is characterized in that, comprises the steps: S1: Select a defect-free TC4 titanium alloy sample for grinding and straightening; S2: prefabricating grooves on the surface of the TC4 titanium alloy so as to add silver particles; S3: Fill and scatter silver particles in the prefabricated grooves, and then process them on the workbench of the friction stir welding equipment under the protection of argon gas. 2. the superfine modification method to TC4 titanium alloy surface as claimed in claim 1, is characterized in that, the smelting method of described TC4 titanium alloy is vacuum consumable furnace smelting. 3. the superfine modification method to TC4 titanium alloy surface as claimed in claim 2, is characterized in that, the operation of described vacuum consumable furnace smelting is: After the Ti-6Al-4V alloy is smelted three times, the material is forged above the β phase transformation point of the Ti-6Al-4V alloy, and then the temperature-controlled forging is carried out in the α+β phase region of the Ti-6Al-4V alloy , and finally hot rolling; Wherein, the blank forging temperature is 1010-1050°C, and the temperature-controlled forging and hot rolling temperature is 920-950°C. 4. The method for superfine modification of the surface of TC4 titanium alloy according to claim 1, wherein the depth of the groove is 0.5-2mm. 5. the superfine modification method to TC4 titanium alloy surface as claimed in claim 1, is characterized in that, described straightening adopts four-roller cold straightening machine. 6. the superfine modification method to TC4 titanium alloy surface as claimed in claim 1, it is characterized in that, in step S3, the stirring head processing speed of described friction stir welding equipment is 50mm/min, and stirring head rotational speed It is 225～375r/min. 7. The method for superfine modification of the surface of TC4 titanium alloy according to claim 1, characterized in that, in step S3, the depth of pressing the shoulder of the friction stir welding equipment into the surface of the sample is controlled to be 0.3 to 0.5 mm. 8. The method for superfine modification of the surface of TC4 titanium alloy as claimed in claim 1, wherein the average particle diameter of the silver particles is 50nm.