阅读说明：本技术 提高镁合金力学性能及生物功能稳定性的热处理方法 (Heat treatment method for improving mechanical property and biological function stability of magnesium alloy ) 是由 李贺杰 倪国颖 于 2020-03-03 设计创作，主要内容包括：本发明公开了提高镁合金力学性能及生物功能稳定性的热处理方法,包含以下步骤：(1)将原始的冷拔镁合金AZ31在进行无干扰氛围完全退火处理；(2)将步骤(1)的镁合金AZ31的表面利用水砂纸打磨,消除原始的氧化层,并保持和提升表面的光洁度；(3)将步骤(2)所得的镁合金利用惰性气体或真空无干扰氛围进行加热,将镁合金加热至300-400℃,然后保温3-5小时；(4)将步骤(3)所得的镁合金无干扰氛围完成完全退火处理,随炉冷却至室温,以得到具有组织均匀和各向同性的等轴晶结构。用本方法制备的镁合金AZ31具有良好的组织结构：晶粒尺寸约为16微米,表明硬度约为73HV,具有相对稳定、良好的耐腐蚀性能,与相应的多肽具有良好的结合性能,并能维持涂层的良好生物功能性如抗菌性等。(The invention discloses a heat treatment method for improving the mechanical property and biological function stability of magnesium alloy, which comprises the following steps: (1) completely annealing the original cold-drawn magnesium alloy AZ31 in an interference-free atmosphere; (2) polishing the surface of the magnesium alloy AZ31 obtained in the step (1) by using water sand paper, eliminating an original oxide layer, and keeping and improving the surface smoothness; (3) heating the magnesium alloy obtained in the step (2) by using inert gas or vacuum interference-free atmosphere, heating the magnesium alloy to 300-400 ℃, and then preserving heat for 3-5 hours; (4) and (4) completing complete annealing treatment of the magnesium alloy obtained in the step (3) in an interference-free atmosphere, and cooling the magnesium alloy to room temperature along with a furnace to obtain an isometric crystal structure with uniform and isotropic structure. The magnesium alloy AZ31 prepared by the method has a good tissue structure: the grain size is about 16 microns, the hardness is about 73HV, the coating has relative stability and good corrosion resistance, has good binding performance with corresponding polypeptide, and can maintain good biological functionality, such as antibacterial property and the like, of the coating.)

1. The heat treatment method for improving the mechanical property and the biological function stability of the magnesium alloy is characterized by comprising the following steps of:

(1) completely annealing the original cold-drawn magnesium alloy AZ31 in an interference-free atmosphere with original processing stress eliminated and special structure texture eliminated;

(2) polishing the surface of the magnesium alloy AZ31 obtained in the step (1) by using water sand paper, eliminating an original oxide layer, and keeping and improving the surface smoothness;

(3) heating the magnesium alloy AZ31 obtained in the step (2) by using inert gas or vacuum to manufacture an interference-free atmosphere, heating the magnesium alloy AZ31 to 300-350 ℃ in the inert gas atmosphere, and then preserving heat for 3-4 hours;

(4) and (4) completing complete annealing treatment on the magnesium alloy AZ31 obtained in the step (3) by utilizing an interference-free atmosphere of inert gas, and cooling to room temperature along with a furnace to obtain an isometric crystal structure with uniform and isotropic structure.

2. The heat treatment method for improving the mechanical property and the biological function stability of the magnesium alloy as claimed in claim, characterized in that: the surface of the magnesium alloy AZ31 is ground by water sand paper, including primary grinding and polishing; the primary grinding is carried out by using water sand paper with 400 meshes, and grinding is carried out for 1-3 minutes, so that an original oxide layer is eliminated; then immediately polishing, wherein the polishing is carried out by using water sand paper 1200-2400 meshes, and the surface finish of the magnesium alloy AZ31 is kept for 2-5 minutes.

3. The heat treatment method for improving the mechanical property and the biological function stability of the magnesium alloy according to claim 2, wherein: the primary grinding is carried out according to one direction, the oxide layer can be effectively removed according to the force requirement, and the primary grinding is carried out until the dark oxide layer is completely removed from the surface of the magnesium alloy AZ31, so that silver-white magnesium metal is generated; the grinding direction in the polishing process is vertical to the primary grinding direction, and the force is smaller than that of primary grinding until no obvious scratch is formed on the surface of the magnesium alloy AZ 31.

Technical Field

The invention relates to a metal treatment method, in particular to a heat treatment method for improving the mechanical property and the biological function stability of magnesium alloy.

Background

With the development of human society and the increase of human activities, the damage of human bone tissues and hard tissues is more and more frequent, and thus the requirements for fixing, repairing and replacing corresponding bone tissues as well as biomaterials are more and more demanding.

The traditional bone fixing and replacing materials such as titanium alloy, stainless steel and other metal materials have large difference with the elastic modulus of human bone tissues and the mechanical property of human bones, so once the bone fixing and replacing materials are implanted into a human body, a plurality of problems are easy to occur: stress shielding, localized PH changes due to the release of metal ions, and thus, an intermediate infectious or inflammatory response. Thus, biocompatibility is poor and adaptation to the bone healing process is difficult. The polymer material has poor mechanical properties, particularly poor plasticity, toughness and radial mechanical properties, so that the polymer material cannot be widely applied as a bone substitute material.

As a typical light alloy, the magnesium alloy AZ31 has almost the same elastic modulus with human bones, so the magnesium alloy AZ31 is close to the mechanical properties of the human bones and is an ideal human bone substitute material. In addition, magnesium is an essential component for human metabolism and biological reaction, and magnesium has a good promoting effect on bone growth and strengthening through the combination with osteoblasts. Magnesium has good biocompatibility as a bone substitute material.

However, because magnesium is active in chemical property, in the human body environment, due to the existence of a plurality of ions, the degradation rate of the magnesium and magnesium alloy AZ31 transplantation material is fast, and further the pH value of the local body fluid environment is obviously increased, so that alkalosis can be caused, local inflammatory reaction can be caused, and cells can be dead. Therefore, the control of the degradation rate of the magnesium alloy AZ31 in vivo becomes a key problem for the application of the magnesium alloy AZ31 as a bone grafting material.

In order to solve the problem of too rapid degradation of the magnesium alloy AZ31 in vivo, many methods have been used to improve the corrosion resistance of magnesium, and various physical and chemical methods have been used to strengthen the surface. At present, in order to make the material have more biological activity and biocompatibility, various coatings with biological functions are generated; however, due to the defects of the magnesium alloy AZ31, the functionality of the coating on the surface of the material is reduced, the activity of the coating is reduced, and the use of the material is influenced.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a heat treatment method for improving the mechanical property and biological function stability of the magnesium alloy, and the magnesium alloy added by the method has a good tissue structure, has good binding property with corresponding polypeptide, and can maintain good biological functions of a coating, such as antibacterial property and the like.

In order to solve the technical problems, the invention adopts the following technical means:

the heat treatment method for improving the mechanical property and the biological function stability of the magnesium alloy comprises the following steps:

(1) completely annealing the original cold-drawn magnesium alloy AZ31 in an interference-free atmosphere with original processing stress eliminated and special structure texture eliminated;

(2) polishing the surface of the magnesium alloy AZ31 obtained in the step (1) by using water sand paper, eliminating an original oxide layer, and keeping and improving the surface smoothness;

(3) heating the magnesium alloy AZ31 obtained in the step (2) by using inert gas or vacuum to manufacture an interference-free atmosphere, heating the magnesium alloy AZ31 to 330-350 ℃ in the inert gas atmosphere, and then preserving heat for 3-4 hours;

(4) and (4) completing complete annealing treatment on the magnesium alloy AZ31 obtained in the step (3) by utilizing an interference-free atmosphere of inert gas, and cooling to room temperature along with a furnace to obtain an isometric crystal structure with uniform and isotropic structure.

The magnesium alloy AZ31 prepared by the method has a good tissue structure: the grain size is about 16 microns, the hardness is about 73HV, the polypeptide has good binding performance with the corresponding polypeptide, and good biological functionality, such as antibacterial property and the like, of the coating can be maintained.

The further preferred technical scheme is as follows:

the surface of the magnesium alloy AZ31 is ground by water sand paper, including primary grinding and polishing; the primary grinding is carried out by using water sand paper with 400 meshes, and grinding is carried out for 1-3 minutes, so that an original oxide layer is eliminated; then immediately polishing, wherein the polishing is carried out by using water sand paper 1200-2400 meshes, and the surface finish of the magnesium alloy AZ31 is kept for 2-5 minutes.

The polishing mode is helpful for removing the oxide layer on the surface of the magnesium alloy AZ31, and the surface is clean and has good smoothness.

The primary grinding is carried out according to one direction, the oxide layer can be effectively removed according to the force requirement, and the primary grinding is carried out until the dark oxide layer is completely removed from the surface of the magnesium alloy AZ31, so that silver-white magnesium metal is generated; the grinding direction in the polishing process is vertical to the primary grinding direction, and the force is smaller than that of primary grinding until no obvious scratch is formed on the surface of the magnesium alloy AZ 31.

The polishing mode is helpful for removing the oxide layer on the surface of the magnesium alloy AZ31, and the surface is clean and has good smoothness.

Drawings

FIG. 1 is a schematic view of a non-interference atmosphere complete annealing.

FIG. 2 is a comparison of the structure of AZ31 magnesium alloy AZ31 after annealing compared to the structure of the original drawn AZ31 magnesium alloy AZ31, in which (a) the structure of the untreated cold drawn AZ31 magnesium alloy AZ 31; (b) and the AZ31 magnesium alloy AZ31 structure is completely annealed in a non-interference atmosphere.

Fig. 3 is a schematic structural diagram of a bone nail made of magnesium alloy according to the method.

FIG. 4 is a comparison graph of the antibacterial reaction of the annealed AZ31 magnesium alloy AZ31 after being combined with small molecule polypeptide, wherein, the graph A is a 24-hour antibacterial reaction graph of a magnesium alloy AZ31 chelated small molecule peptide F3 sample; FIG. B is a 48-hour bacteriostatic reaction diagram of a magnesium alloy AZ31 chelated small molecule peptide F3 sample; the graph C is a 24-hour bacteriostatic reaction graph of an original cold-drawn peptide AZ31 chelated small molecule peptide F3 sample; and the graph D is a 48-hour bacteriostatic reaction graph of an original cold-drawn peptide AZ31 chelated small-molecule peptide F3 sample.

FIG. 5 is a schematic structural diagram of a sample obtained by an in-vitro corrosion experiment made of the magnesium alloy according to the method.

FIG. 6 shows the pH change of the samples of AZ31 magnesium alloy after annealing, cold-extruded magnesium alloy and pure magnesium alloy after 5 days of in vitro corrosion test.

FIG. 7 shows the weight values of samples of AZ31 magnesium alloy after annealing, cold-extruded magnesium alloy and pure magnesium alloy after annealing after 5 days of in vitro corrosion test.

FIG. 8 is the surface topography of the sample after 5 days of in vitro corrosion testing. A: the surface appearance of the AZ31 sample before in-vitro corrosion is cold-drawn; b, surface appearance of the AZ31 sample before in-vitro corrosion after annealing; c: the surface appearance of the AZ31 sample after being corroded for 120 hours in vitro is cold drawn; and D, the surface appearance of the AZ31 sample after annealing and in-vitro corrosion for 120 hours.

Detailed Description

The present invention will be further described with reference to the following examples.

Referring to fig. 1 to 4, the heat treatment method for improving the mechanical property and the biological function stability of the magnesium alloy according to the present invention includes the following steps:

(1) completely annealing the original cold-drawn magnesium alloy AZ31 in an interference-free atmosphere with original processing stress eliminated and special structure texture eliminated;

(2) polishing the surface of the magnesium alloy AZ31 obtained in the step (1) by using water sand paper, eliminating an original oxide layer, and keeping and improving the surface smoothness; the surface of the magnesium alloy AZ31 is ground by water sand paper, including primary grinding and polishing; the primary grinding is carried out by using water sand paper with 400 meshes, and grinding is carried out for 1-3 minutes, so that an original oxide layer is eliminated; then immediately polishing, wherein the polishing is carried out by using water sand paper 1200-2400 meshes, and the surface finish of the magnesium alloy AZ31 is kept for 2-5 minutes; the primary grinding is carried out according to one direction, the oxide layer can be effectively removed according to the force requirement, and the primary grinding is carried out until the dark oxide layer is completely removed from the surface of the magnesium alloy AZ31, so that silver-white magnesium metal is generated; the grinding direction in the polishing process is vertical to the primary grinding direction, and the force is smaller than that of primary grinding until no obvious scratch is formed on the surface of the magnesium alloy AZ 31;

(3) heating the magnesium alloy AZ31 obtained in the step (2) by using inert gas or vacuum to manufacture an interference-free atmosphere, heating the magnesium alloy AZ31 to 330-350 ℃ in the inert gas atmosphere, and then preserving heat for 3-5 hours, wherein the 3-5 hours are t1-t2 time in the picture 1;

(4) and (4) completing complete annealing treatment on the magnesium alloy AZ31 obtained in the step (3) by utilizing an interference-free atmosphere of inert gas, and cooling to room temperature along with a furnace to obtain an isometric crystal structure with uniform and isotropic structure.

Metallographic structure observation was performed by a field emission scanning electron microscope, and the microstructure of AZ31 before and after heat treatment was compared. The grain size of the AZ31 magnesium alloy AZ31 after annealing was 15.8 microns and the grain size of the original cold drawn magnesium alloy AZ31 was 9.2 microns. The hardness of AZ31 was measured by a Vickers microhardness tester to compare the change in Vickers hardness before and after heat treatment. The Vickers hardness of untreated AZ31 was 83.9HV, while that of AZ31 after complete annealing in a non-interfering atmosphere was 72.8 HV.

The bacteriostasis comparative experiment comprises the following steps:

(1) the original cold-drawn magnesium alloy AZ31 and the AZ31 of the method are made into small-size bone nails with the diameter of 0.5mm and the length of 2mm, and the size tolerance is +/-0.005 mm;

(2) combining two small-size bone nails processed by two alloys with polypeptide F3 of a small molecule through a chelation reaction, and respectively generating a layer of small peptide F3 coating on the surface of each bone nail;

(3) two magnesium alloy AZ31 samples after chelation reaction were subjected to a 48-hour bacteriostatic test of drug-resistant Staphylococcus aureus to observe the antibacterial properties of the two materials, and the results are shown in the following table:

table 1: and (5) comparing the bacteriostatic effect.

(4) The analysis leads to the experimental conclusion: comparing the experimental results, it can be seen that: compared with magnesium alloy AZ31 chelated with small peptide F3 in a cold-drawn state, the magnesium alloy AZ31 sample subjected to interference-free ambient complete annealing treatment has more stable and durable antibacterial performance after being chelated with polypeptide F3: the antibacterial agent can keep good antibacterial performance against drug-resistant staphylococcus aureus within 48 hours; and after the cold-drawn AZ31 is chelated with the polypeptide F3, the antibacterial effect on the drug-resistant staphylococcus aureus is completely lost after 48 hours.

(II) in vitro corrosion comparison experiment as follows:

(1) the original cold-drawn magnesium alloy AZ31 and the AZ31 prepared by the method are made into small-size magnesium sheets with the diameter of 4.4mm and the thickness of 2mm, and the dimensional tolerance is +/-0.002 mm;

(2) putting the two metal samples into a DMEM (Dulbecco's Modified Eagle Medium) high-sugar culture Medium, and carrying out an in-vitro corrosion resistance test for 120 hours in a constant-temperature incubator at 37 ℃;

(3) in the in vitro corrosion process, the weight of the sample and the pH value of the DMEM medium are detected regularly. The specific observation contents and steps and observation results are as follows:

table 2: comparison of in vitro Corrosion test results

(4) After the in vitro corrosion test was completed, the surface topography of the two samples was observed using SEM.

(5) The analysis leads to the experimental conclusion: comparing the experimental results, it can be seen that: compared with the magnesium alloy AZ31 in a cold-drawn state, the magnesium alloy AZ31 sample subjected to interference-free ambient complete annealing treatment has more stable and durable corrosion resistance: can be in DMEM within 120 hours; and the cold-drawn AZ31 has accelerated corrosion after 48 hours, accelerated sample weight loss and no corrosion resistance to DMEM. Through observation of surface morphology, when the corrosion is 120 hours, a large amount of obvious laminar or scaly peeled objects are formed on the surface of the magnesium alloy AZ31 in a cold-drawn state, and the surface corrosion is obvious; and the AZ31 surface which is completely annealed in an interference-free atmosphere has no obvious layered or scaly exfoliation, and the surface is kept relatively intact.

The method of the embodiment has the advantages of simple process, convenient operation and strong feasibility, and the formed new material is stable and is combined with other materials to form a stable structure; the activity of the binding product can be maintained and strengthened; low energy consumption, easy production, short period, easy industrialization and no pollution to the environment.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, which is defined in the appended claims.