A design and preparation method of a high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy

Abstract

The application relates to the technical field of alloy materials, in particular to a design and preparation method of a high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy. A physical metallurgical model and machine learning are combined to design a beta-type biomedical titanium alloy with a low elastic modulus, titanium alloy plate is prepared through cold working deformation, and finally, the cold-rolled plate is further strengthened through short-time low-temperature deformation aging treatment. The Ti-Mo-Nb-Zr-Sn alloy obtained through the application has excellent high-strength low-modulus performance, the tensile strength R m is not lower than 775 MPa, the elastic modulus E is not higher than 45 GPa, and the strength modulus ratio is at most 22.2*10 ‑3 From the perspective of the strength modulus ratio, on the basis of the low elastic modulus, the deformation aging treatment significantly improves the mechanical compatibility of the alloy, the performance demand is met, and the stress shielding phenomenon can be effectively improved, so that the alloy can be used as a potential medical fixing material in clinical application.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of alloy materials, in particular to a design and preparation method of a high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy. BACKGROUND

[0002] Titanium and titanium alloys have high specific strength, good corrosion resistance, excellent biocompatibility and low elastic modulus, and are widely used in the field of orthopedic implant materials such as artificial joints, spinal orthopedic internal fixation systems and dental implants. The development of medical titanium alloys has experienced three stages. The first generation of medical titanium alloys is pure titanium and Ti-6Al-4V. The second generation includes alpha + beta type titanium alloys represented by Ti-6Al-7Nb, but Al and V have cytotoxicity and can cause malignant tissue reactions. In addition, the elastic modulus of the first and second generations of medical titanium alloys is much higher than that of human bone (10-30 GPa), which leads to a mismatch in the elastic modulus between the implanted material and human bone, easily causing a "stress shielding effect", and long-term implantation in the human body can cause secondary damage to patients. Therefore, in order to meet the clinical needs of medical implant materials, it is extremely important to develop the third generation of beta type medical titanium alloys with better biocompatibility and mechanical properties.

[0003] At present, the semi-quantitative method of traditional alloy design for medical titanium alloys cannot quickly realize the precise design of the composition, resulting in a huge time and economic cost of a large number of trial and error, verification, re-trial and re-verification. Chinese invention patent (publication number CN115410670A) biological medical titanium alloy with excellent elastic modulus and construction and preparation method, characterized by combining machine learning big data training and design as a theoretical guidance basis, through big data analysis learning combined with experiments, successfully constructed a full beta grain structure Ti 54 Zr 18-x-y Nb 13+x Mo 15+y biomedical titanium alloy with low elastic modulus, and broke the traditional trial and error method of preparing alloys, and obtained a reliable alloy composition range in a shorter time.

[0004] Chinese invention patent (publication number CN116590551A) discloses a high-strength low-modulus Ti-Nb-Zr biomedical titanium alloy and a preparation method thereof. The main feature of this patent is to control the deformation amount in the cold working process to be greater than 90%, thereby reducing the elastic modulus of the alloy and increasing the tensile strength of the alloy. However, its elastic modulus is still much higher than that of human bone, and the "strength modulus ratio (ratio of tensile strength to elastic modulus)" of the alloy has not been significantly improved.

[0005] A Chinese invention patent (publication number CN111676407B) discloses a high-strength low-elastic modulus medical implant zirconium alloy and a preparation method. The main feature of the patent is that through aging treatment, the alloy precipitates alpha phase with significant dispersion strengthening effect in the low modulus beta matrix, which can significantly improve the strength of the alloy, but the high modulus alpha phase precipitated during the aging process will also increase the elastic modulus of the alloy. SUMMARY

[0006] In view of the problems that the current biomedical titanium alloy still has a relatively high elastic modulus, and the traditional component design method of medical titanium alloy has a long development cycle and high cost, the purpose of the present application is to provide a design and preparation method of high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, which adopts a low-elasticity modulus medical titanium alloy design method combining physical metallurgy model and machine learning, and strengthens the low-elasticity modulus alloy through deformation aging treatment, and develops a beta type medical titanium alloy with high strength and low modulus in the Ti-Mo-Nb-Zr-Sn alloy system.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] A design and preparation method of high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, which is carried out according to the following steps:

[0009] (1) Collect existing literature to create a low-elasticity modulus medical titanium alloy dataset, with alloy composition (C i ) as input and elastic modulus (E) as output, and Mo equivalent and valence electron concentration representing the stability of beta phase structure as characteristic parameters embedded in the dataset;

[0010] (2) Establish the relationship E=f(C i ) to predict the elastic modulus of Ti-Mo-Nb-Zr-Sn alloy;

[0011] (3) Construct the composition space of low-modulus alloy, add Mo equivalent, valence electron concentration and d-electron theory three physical metallurgy models to constrain the composition and phase composition of the alloy, wherein: [Mo eq ] is 13-15, is 2.84-2.90, is 2.40-2.46, and e / a is 4.20-4.24;

[0012] (4) Encode the alloy population that meets the three constraints by means of genetic algorithm, calculate the fitness of each alloy according to the predicted value of the elastic modulus of the alloy, and find the optimal composition that meets the conditions after 400 iterations or less;

[0013] (5) The alloy composition smelted titanium alloy ingot predicted according to the machine learning method, and the chemical composition is as follows in percentage by mass: Mo: 0-4.5%, Nb: 23.5-37.5%, Zr: 0-2.9%, Sn: 0-2.5%, and the rest is Ti;

[0014] (6) According to the titanium alloy composition, each component is proportionally prepared with Ti, Mo, Nb, Zr and Sn as raw materials, smelted in a vacuum non-consumable arc furnace, turned over 4-5 times, and a titanium alloy ingot is obtained, and the titanium alloy ingot is kept at 1000-1200℃ for 2-4h in a high-purity Ar gas environment;

[0015] (7) The titanium alloy ingot is kept at 800℃ for 5-10min and then hot-rolled, and intermediate annealing is performed every pass, and the total deformation amount of hot rolling is controlled to be 75-85%, and a hot-rolled plate is obtained;

[0016] (8) The hot-rolled plate is polished on the surface, the roughness is controlled to be greater than 1.6, and the cold rolling deformation amount is controlled to be 60-80%, and the deformation amount of single cold rolling treatment is 0.5-2%, and a cold-rolled plate is obtained.

[0017] In step (1) of the design and preparation method of the high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, a low-elasticity modulus medical titanium alloy data set is collected from existing literature, which contains 75 different alloy compositions and their corresponding elastic moduli in solid solution, and the alloy composition (C i ) is taken as input, and the elastic modulus (E) is taken as output, and an XGBoost regression model is introduced to establish the relationship E=f(C i ), and the R 2 value is closer to 1, indicating that the model has better fitting degree on the data, smaller error and higher accuracy, and the R 2 value is greater than 0.95.

[0018] In step (3) of the design and preparation method of the high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, three physical metallurgy models of Mo equivalent, valence electron concentration and d-electron theory are added to constrain the composition and phase composition of the alloy, and the optimal constraint conditions are as follows:

[0019] Minimize E(a,b,c,d,e)

[0020] Subject to GA(a,b,c,d,e)

[0021] 13.0≤[Mo eq ](a,b,c,d,e)≤15.0

[0022]

[0023] 4.20≤e / a(a,b,c,d,e)≤4.24

[0024] Wherein, a, b, c, d, e represent the content of Ti, Mo, Nb, Zr, Sn in Ti-Mo-Nb-Zr-Sn alloy system; E(a, b, c, d, e) is the elastic modulus prediction value of the Ti-Mo-Nb-Zr-Sn alloy designed under the constraint of the optimization model; GA(a, b, c, d, e) is the optimal alloy composition screened out by combining with genetic algorithm optimization based on the common guidance of three physical metallurgy models; [Mo eq ](a, b, c, d, e) is the Mo equivalent value corresponding to the alloy; e / a(a, b, c, d, e) is the average valence electron concentration ratio corresponding to the alloy; And is the value of d-electron theory corresponding to the alloy And value.

[0025] In the design and preparation method of the high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, in step (8), the phase composition of the cold-rolled plate in the cold-rolled state is β+α″ phase, and the β phase accounts for 90-93% and the α″ phase accounts for 7-10% in terms of volume percentage.

[0026] In the design and preparation method of the high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, in step (8), the cold-rolled plate is subjected to deformation aging treatment at 350-450℃ for 10-40min in a high-purity Ar gas environment to obtain the biomedical titanium alloy finished plate.

[0027] In the design and preparation method of the high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, the phase composition of the deformation aging state alloy of the biomedical titanium alloy finished plate is β+α phase, and the β phase accounts for 95-97% and the α phase accounts for 3-5% in terms of volume percentage.

[0028] In the design and preparation method of the high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, the final performance of the biomedical titanium alloy finished plate is: the tensile strength R m No less than 775MPa, the elastic modulus E no higher than 45GPa, the elongation At no less than 10%, and the "strong modulus ratio" no less than 20.0×10 -3 .

[0029] The high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy design preparation method, in step (8), the cold-rolled plate is subjected to solid solution treatment at 750-850 DEG C for 1-1.5 h under a high-purity Ar gas environment and then water-cooled to room temperature, which is used to verify the phase composition and elastic modulus of the titanium alloy.

[0030] The high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy design preparation method, the solid solution state alloy of the cold-rolled plate is a full beta grain structure, and the grain size is 30-50 mu m.

[0031] Compared with the prior art, the present application has the following beneficial technical effects:

[0032] 1. In the component design, Mo, Nb, Zr and Sn, all of which are beta stable elements, are added, and they have good biocompatibility with human tissues and cannot cause diseases, and at the same time have an elastic modulus comparable to that of human bones, which can effectively avoid the "stress shielding effect".

[0033] 2. The present application breaks the traditional trial-and-error method of preparing alloys, and under the theoretical guidance of physical metallurgy, combined with machine learning and big data training, a multi-element alloy with specific properties is designed in a shorter time, which reduces the cost of alloy development and improves the design efficiency of the alloy.

[0034] 3. The phase composition constraint added in the component design can obtain a full beta phase structure with strong phase stability, and the alloy will not precipitate a second phase to deteriorate the elastic modulus of the alloy after quenching within a certain component range, which has a certain fault tolerance for the actual production deviating from the designed component.

[0035] 4. The present application adopts the strengthening method of deformation aging treatment, which causes inverse martensite phase change to make the alpha double prime phase generated in the cold rolling process into low elastic modulus beta phase and a small amount of nanoscale alpha phase, thereby maintaining low elastic modulus while improving strength, and the modulus of the alloy obtained after strengthening is similar to that of human bones, which can be used as a bone graft or medical device.

[0036] 5. The preparation method of the high-strength low-modulus biomedical titanium alloy provided by the present application greatly improves the development efficiency of the alloy. With the help of machine learning, medical titanium alloy is designed, which reduces the cost of alloy design, and at the same time, the prepared alloy has not only low elastic modulus but also high tensile strength, thereby improving the biomechanical properties of beta type medical titanium alloy and further widening its application field. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The high-strength low-modulus biomedical titanium alloy design method flow chart of the present application.

[0038] Figure 2 The fitting results of the XGBoost (Extreme Gradient Boosting) algorithm modeling in the present application. In the figure, the horizontal axis Experimental E is the experimental elastic modulus (GPa), and the vertical axis Predicted E by XGB is the elastic modulus (GPa) predicted by XGBoost; Train is the training set, test is the test set, RMSE is the root mean square error, and R 2 R is the determination coefficient.

[0039] Figure 3 The iterative optimization evolution chart of the genetic algorithm embedded with physical metallurgical constraints in the present application. In the figure, the horizontal axis Generation is the generation, the vertical axis E elastic modulus (GPa), Best Objective Value is the best objective value, and Average Objective Value is the average objective value.

[0040] Figure 4 The EBSD phase composition distribution chart of the solution treated alloy in Example 1.

[0041] Figure 5 The EBSD phase composition distribution chart of the deformed and aged alloy in Example 1.

[0042] Figure 6 The engineering stress-strain curve of the solution treated alloy in Example 1. In the figure, the horizontal axis Engineering Strain is the engineering strain (%), and the vertical axis Engineering Stress is the engineering stress (MPa).

[0043] Figure 7 The engineering stress-strain curve of the deformed and aged alloy in Example 1. In the figure, the horizontal axis Engineering Strain is the engineering strain (%), and the vertical axis Engineering Stress is the engineering stress (MPa).

[0044] Figure 8 The engineering stress-strain curve of the solution treated and deformed and aged alloys in Example 2. In the figure, the horizontal axis Engineering Strain is the engineering strain (%), and the vertical axis Engineering Stress is the engineering stress (MPa).

[0045] Figure 9Engineering Stress-Strain curves for the solution and the wrought and aged alloys of Example 3. In the figure, the horizontal axis Engineering Strain is engineering strain (%), and the vertical axis Engineering Stress is engineering stress (MPa). DETAILED DESCRIPTION

[0046] In the detailed implementation, as shown in Figure 1 , the present application proposes a design and preparation method of high-strength and low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, and the process includes two parts:

[0047] The first part is to design the composition of the low-elasticity modulus medical titanium alloy based on machine learning, which is specifically performed according to the following steps:

[0048] 1. Establish the original data set and determine the characteristic parameters

[0049] Based on the existing literature, a data set of Ti-Mo-Nb-Zr-Sn low-elasticity modulus β-type medical titanium alloy is created, and the output parameters in the data set are all the experimental values of the elastic modulus of the sample alloy in the solution state. The phase composition is single β phase or contains a small amount of α" phase on the β matrix, and they are all obtained by solid solution treatment and rapid cooling, which ensures the accuracy of the data set samples.

[0050] As shown in Figure 2 , the Mo equivalent [Mo eq ] value and the valence electron concentration e / a value representing the elastic modulus are embedded as characteristic parameters into the data set, and the data set is randomly divided into a training set and a test set in a ratio of 9:1, that is, 90% of the data is used for training each model, and 10% of the data is used for detecting the prediction performance of the model. Considering that the data set is a small sample problem, the data set is randomly divided 500 times by using 10-fold cross-validation method, and is used as training set and test set in turn to ensure the full use of data.

[0051] 2. XGBoost model predicts target value (elastic modulus)

[0052] As shown in Figure 2 , the statistical values of RMSE and R 2 are used as the basis for hyperparameter tuning of the model. After grid search tuning, the XGBoost algorithm is used to establish a machine learning model, and the elastic modulus model is evaluated according to RMSE and R 2 . In the present application, the R 2 value of the XGBoost prediction model is all above 0.95.

[0053] 3. Add physical metallurgy constraints and create an initial population

[0054] In the Ti-Mo-Nb-Zr-Sn alloy, the Mo equivalent, the average valence electron concentration and the d-electron theory three physical metallurgy are added to the alloy phase composition and the composition constraint, and the specific optimal constraint is: the Mo equivalent value [Mo eq ]: 13.0-15.0, the average valence electron concentration ratio e / a: 4.20-4.24, the average bond order 2.84-2.90, the average d-electron orbital energy level 2.40-2.46, the alloy meeting the constraint condition is used as the initial population.

[0055] 4. Predicting elastic modulus and determining alloy composition

[0056] As Figure 3 shown, the elastic modulus prediction value of the initial population is determined by the XGBoost prediction model, the fitness of each alloy is calculated according to the elastic modulus value of the alloy in the created initial population, and the composition range of Ti, Mo, Nb, Zr and Sn of the alloy is found when the elastic modulus minimum value is found by combining the genetic algorithm optimization.

[0057] The alloy composition chemical composition predicted by the machine learning method is: Mo: 0-4.5%, Nb: 23.5-37.5%, Zr: 0-2.9%, Sn: 0-2.5%, and the rest is Ti; wherein: Mo is preferably 0.5-4.5%, Zr is preferably 0.5-2.9%, and Sn is preferably 1.0-2.5%.

[0058] The second part is to prepare the Ti-Mo-Nb-Zr-Sn low modulus alloy meeting the constraint, to prepare the alloy ingot by vacuum arc furnace melting and cold working deformation, and to strengthen on the basis of low modulus by means of deformation aging treatment, and to complete the alloy microstructure phase composition analysis and performance test, and to obtain a high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy.

[0059] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below, the illustrative embodiments of the present application and the description thereof are only used to explain the present application, and do not limit the present application.

[0060] Example 1

[0061] In this embodiment, a design and preparation method of a high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, specifically comprising the following steps:

[0062] 1. The preparation of the alloy sample is completed by using non-consumable vacuum melting furnace according to the designed composition, and the composition is Mo: 0.5%, Nb: 36.5%, Zr: 0.8%, Sn: 1.6% by weight percentage, and the rest is Ti.

[0063] 2. The alloy is melted by using non-consumable vacuum arc furnace to melt into button ingot by using pure Ti (purity 99.99wt%), Mo (purity 99.99wt%), Nb (purity 99.95wt%), Zr (purity 99.99wt%) and Sn (purity 99.95wt%) as raw materials, and the alloy is repeatedly flipped and melted for 5 times by connecting the current to ensure the uniformity of the composition of the alloy.

[0064] 3. The button ingot after melting is subjected to homogenization treatment, and the button ingot is kept at 1000℃ for 2h under high-purity Ar gas (volume purity 99.9999%, the same below) and then water-cooled to room temperature.

[0065] 4. The button ingot is subjected to hot rolling after keeping at 800℃ for 10min, and intermediate annealing is carried out every pass, and the total deformation of hot rolling is 80%.

[0066] 5. After the hot-rolled plate is cooled to room temperature, the hot-rolled plate is subjected to multi-pass rolling on a cold rolling mill, and the average pass reduction is 1.5%, and the final reduction is 60%. The cold-rolled plate has a cold-rolled alloy phase composition of β+α" phase, and the β phase accounts for 93% and the α" phase accounts for 7% by volume percentage.

[0067] 6. Two groups of heat treatment are carried out on the cold-rolled plate respectively: one group is subjected to solid solution treatment for verifying the phase composition and elastic modulus of the alloy, and the cold-rolled plate is kept at 800℃ for 1h under high-purity Ar gas and then water-cooled to room temperature; the other group is subjected to deformation aging treatment, and the cold-rolled plate is kept at 400℃ for 20min under high-purity Ar gas and then water-cooled to room temperature, and finally the finished plate of the medical titanium alloy with high strength and low modulus is obtained.

[0068] 7. According to the phase composition analysis of Figure 4 , it can be known that the phase composition of the solid solution Ti-0.5Mo-36.5Nb-0.8Zr-1.6Sn alloy is mainly green equiaxed β phase without second phase precipitation, and the average grain size is about 37μm, which meets the added phase composition constraint. From Figure 5 , it can be known that the alloy after deformation aging treatment can significantly improve the strength of the alloy under the joint action of fine grains and second phase, and due to the short aging time, the reverse martensite phase transformation occurs to make the α" phase generated in the cold rolling process into low elastic modulus β phase and a small amount of nanoscale α strengthening phase, and the β phase accounts for 97% and the α phase accounts for 3% by volume percentage, which has little effect on the elastic modulus.

[0069] 8. Room temperature tensile test was performed on the sample by using AG-X plus 100kN universal tensile testing machine, the tensile rate was 0.5mm / min during the test, and an extensometer was installed to accurately measure the change of gauge length displacement. In order to ensure the reliability of the experiment, three parallel samples were prepared for tensile test, and the average value of the test results was taken as the final result of the mechanical properties.

[0070] 9. By Figure 6 The stress-strain curve of the solid solution alloy shows that the yield strength R p0.2 of the alloy is 428MPa, the tensile strength R m is 608MPa. According to Hooke's law, the slope in the elastic deformation stage is the elastic modulus of the alloy, and in this embodiment, the experimental value of the elastic modulus E of the alloy is 35GPa, which is close to the elastic modulus of human bone, and is consistent with the predicted value of 38GPa.

[0071] 10. From Figure 7 The stress-strain curve of the deformed and aged alloy shows that, compared with the solid solution state, after the alloy is cold-rolled and aged at 400℃ for 20min, a good combination of high strength and low modulus is achieved, the yield strength R p0.2 is 685MPa, the tensile strength is R m 778 MPa, the elastic modulus E is 35GPa, the elongation At is 10.1%, and the "strength modulus ratio" is 22.2x10 -3 .

[0072] Embodiment 2

[0073] In this embodiment, a design and preparation method of a high-strength and low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy is provided, which specifically comprises the following steps:

[0074] 1. The alloy sample is prepared by using a non-consumable vacuum melting furnace according to the designed composition, and the composition is Mo: 4.2%, Nb: 24.6%, Zr: 2.9% by weight, and the rest is Ti.

[0075] 2. The alloy is melted by using a non-consumable vacuum arc furnace with pure Ti (purity 99.99wt%), Mo (purity 99.99wt%), Nb (purity 99.95wt%) and Zr (purity 99.99wt%) as raw materials, and the button ingot is repeatedly flipped and melted for 5 times by connecting the current to the arc to ensure the uniformity of the alloy composition.

[0076] 3. The button ingot after melting and casting is subjected to homogenization treatment, and the button ingot is water-cooled to room temperature after being kept at 1000℃ for 2h in a high-purity Ar gas environment.

[0077] 4. The button ingot is hot rolled after being held at 800℃ for 10 minutes, with intermediate annealing performed in each pass. The total deformation during hot rolling is 80%.

[0078] 5. After the hot-rolled sheet cools to room temperature, it is rolled in multiple passes on a cold rolling mill, with an average reduction of 1% per pass and a final reduction of 80%. The cold-rolled alloy phase composition of the sheet is β+α″ phase, with β phase accounting for 90% and α″ phase accounting for 10% by volume percentage.

[0079] 6. Two sets of heat treatments were performed on the cold-rolled sheet: one set was solution treatment to verify the phase composition and elastic modulus of the alloy, in which the cold-rolled sheet was held at 800℃ for 1 hour in a high-purity Ar atmosphere and then water-cooled to room temperature; the other set was deformation aging treatment, in which the cold-rolled sheet was held at 450℃ for 30 minutes in a high-purity Ar atmosphere and then water-cooled to room temperature, finally obtaining a finished sheet of medical titanium alloy with both high strength and low modulus.

[0080] 7. The solution-treated Ti-4.2Mo-24.6Nb-2.9Zr alloy is an equiaxed, all-β phase alloy, conforming to phase composition constraints, with an average grain size of approximately 32 μm. After deformation aging treatment, the alloy's phase composition consists of a matrix β phase and a small amount of α phase. By volume percentage, the β phase accounts for 95% and the α phase accounts for 5%, having little effect on the elastic modulus.

[0081] 8. The samples were subjected to room temperature tensile tests using an AG-X plus 100kN universal tensile testing machine. The tensile rate was 0.5 mm / min. An extensometer was used during the test to accurately measure the change in gauge length displacement. To ensure the reliability of the experiment, three parallel specimens were prepared for tensile testing, and the average value of the test results was taken as the final mechanical property result.

[0082] 9. Through Figure 8 The stress-strain curves of the solid solution alloy show that the yield strength R of the alloy is... p0.2 448MPa, tensile strength R m The elastic modulus is 636 MPa. According to Hooke's Law, the slope during the elastic deformation stage is the elastic modulus of the alloy. In this embodiment, the experimental value of the elastic modulus E of the alloy is 40 GPa, which is close to the elastic modulus of human bone and also matches the predicted value of 43 GPa.

[0083] 10. From Figure 8 The stress-strain curves of the deformation-aged state show that, compared with the solution-treated state, the alloy, after cold rolling and aging at 450℃ for 30 minutes, achieves a good combination of high strength and low modulus, and its yield strength R... p0.2 It has a strength of 732 MPa and a tensile strength of R. m921 MPa, modulus of elasticity E of 42 GPa, elongation At of 10.4%, "strong module ratio" of 21.9 x 10 -3 .

[0084] Example 3

[0085] In this embodiment, a design and preparation method of a high-strength low-modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, specifically comprising the following steps:

[0086] 1. The preparation of the alloy sample is completed by using a non-consumable vacuum melting furnace according to the designed composition, and the composition is Mo: 3.3%, Nb: 29.0%, Sn: 2.1% by weight, and the rest is Ti.

[0087] 2. The alloy melting uses pure metals Ti (purity 99.99wt%), Mo (purity 99.99wt%), Nb (purity 99.95wt%) and Sn (purity 99.95wt%) as raw materials, and adopts a non-consumable vacuum arc furnace to melt into button ingots. The button ingots are repeatedly turned over for 5 times to ensure the uniformity of the alloy composition.

[0088] 3. The button ingot after melting is subjected to homogenization treatment, and the button ingot is heated at 1000℃ for 2h under high-purity Ar gas environment and then water-cooled to room temperature.

[0089] 4. The button ingot is heated at 800℃ for 10min and then hot-rolled, and intermediate annealing is performed after each pass. The total deformation of hot rolling is 80%.

[0090] 5. After the hot-rolled plate is cooled to room temperature, the hot-rolled plate is subjected to multi-pass rolling on a cold rolling mill, and the average pass reduction is 2%. The final reduction is 80%. The cold-rolled plate has a cold-rolled alloy phase composition of β+α" phase, and the β phase accounts for 91% and the α" phase accounts for 9% by volume percentage.

[0091] 6. Two groups of heat treatment are respectively performed on the cold-rolled plate: one group is subjected to solid solution treatment for verifying the phase composition and modulus of elasticity of the alloy, and the cold-rolled plate is heated at 800℃ for 1h under high-purity Ar gas environment and then water-cooled to room temperature; the other group is subjected to deformation aging treatment, and the cold-rolled plate is heated at 400℃ for 20min under high-purity Ar gas environment and then water-cooled to room temperature, so as to finally obtain a finished plate of the biomedical titanium alloy with high strength and low modulus.

[0092] 7. The solid solution state Ti-3.3Mo-29.0Nb-2.1Sn alloy is a full β phase with equiaxed grains, which meets the phase composition constraint, and the average grain size is about 42μm. After the deformation aging treatment of the alloy, the phase composition is a matrix β phase and a small amount of nanoscale α phase, and the β phase accounts for 95% and the α phase accounts for 5% by volume percentage, which has little effect on the modulus of elasticity.

[0093] 8. The room temperature tensile test of the sample is carried out by using an AG-X plus 100kN universal tensile testing machine, the tensile rate is 0.5mm / min during the test, and an extensometer is additionally arranged during the experiment to accurately measure the change amount of the gauge length displacement. In order to ensure the reliability of the experiment, three parallel samples are prepared for tensile test, and the average value of the test results is taken as the final result of the mechanical property.

[0094] 9. By Figure 9 The stress-strain curve result of the solid solution alloy shows that the yield strength R p0.2 of the alloy is 451MPa, the tensile strength R m is 623MPa. According to Hooke's law, the slope in the elastic deformation stage is the elastic modulus of the alloy, and in the embodiment, the experimental value E of the elastic modulus of the alloy is 42GPa, which is close to the elastic modulus of human bone and is consistent with the predicted value 45GPa of the elastic modulus.

[0095] 10. From Figure 9 The stress-strain curve of the deformed aging state shows that, compared with the solid solution state, after the alloy is cold-rolled and aged at 350℃ for 40min, a good combination of high strength and low modulus is realized, the yield strength R p0.2 is 771MPa, the tensile strength is R m is 908MPa, the elastic modulus E is 45GPa, the elongation At is 11.1%, and the "strength modulus ratio" is 20.2x10 -3 .

[0096] The implementation results show that, in the Ti-Mo-Nb-Zr-Sn alloy, the physical metallurgical model and the machine learning are combined to design a beta type medical titanium alloy with low elastic modulus, the titanium alloy plate is prepared by cold working deformation, and finally the cold-rolled plate is further strengthened by short-time low-temperature deformation aging treatment. The Ti-Mo-Nb-Zr-Sn alloy prepared by the method has excellent performance of high strength and low modulus, the tensile strength R m is not less than 775MPa, the elastic modulus E is not higher than 45GPa, the elongation At is not less than 10%, and the "strength modulus ratio" is highest 22.2x10 -3 . From the perspective of the "strength modulus ratio", on the basis of low elastic modulus, the deformation aging treatment significantly improves the mechanical compatibility of the alloy, which can effectively improve the "stress shielding phenomenon" while meeting the performance requirements, and can be used as a potential medical fixation material in clinical application.

Claims

1. A design and fabrication method of high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy, characterized in that, The following steps are taken: (1) Collect existing literature to create a low elastic modulus medical titanium alloy dataset, alloy composition (C i ) as input, elastic modulus (E) as output, and Mo equivalent and valence electron concentration representing the stability of β phase structure as characteristic parameters embedded in the dataset; (2) Establish the relationship of E = f(C i ) for predicting the elastic modulus of Ti-Mo-Nb-Zr-Sn based alloys; (3) Construct the composition space of low modulus alloy, add Mo equivalent, valence electron concentration and d-electron theory three kinds of physical metallurgy model to constrain the composition and phase composition of alloy, wherein: [Mo eq ] is 13-15, is 2.84-2.90, is 2.40-2.46, and e / a is 4.20-4.24; In step (3), the three physical metallurgy models of Mo equivalent, valence electron concentration and d-electron theory are used to constrain the composition and phase composition of the alloy, and the optimal constraint conditions are as follows: Minimize E(a,b,c,d,e) Subject to GA(a,b,c,d,e) 13.0 ≤ [Mo eq ](a,b,c,d,e) ≤ 15.0 4.20≤e / a(a,b,c,d,e)≤4.24 Wherein, a, b, c, d, e represent the content of Ti, Mo, Nb, Zr, Sn in Ti-Mo-Nb-Zr-Sn alloy system; E(a, b, c, d, e) is the elastic modulus prediction value of the Ti-Mo-Nb-Zr-Sn alloy designed under the constraint of the optimization model; GA(a, b, c, d, e) is the optimal alloy composition screened out by combining with genetic algorithm optimization based on the common guidance of three physical metallurgy models; [Mo eq ](a, b, c, d, e) is the Mo equivalent value corresponding to the alloy; e / a(a, b, c, d, e) is the average valence electron concentration ratio corresponding to the alloy; and are the d-electron values in the theory corresponding to the alloy and ; (4) The alloy population that meets the three constraints is coded by means of genetic algorithm, and the fitness of each alloy is calculated according to the predicted value of the elastic modulus. After 400 iterations or less, the optimal composition that meets the conditions is found; (5) According to the alloy composition predicted by the machine learning method, the titanium alloy ingot is melted, and the chemical composition is as follows: Mo: 0-4.5%, Nb: 23.5-37.5%, Zr: 0-2.9%, Sn: 0-2.5%, and the rest is Ti; (6) According to the composition of the titanium alloy, the components are prepared in proportion with Ti, Mo, Nb, Zr and Sn as raw materials, melted in a vacuum non-consumable arc furnace, and turned over 4-5 times to obtain a titanium alloy ingot, and then heat treated at 1000-1200℃ for 2-4h in a high-purity Ar gas environment; (7) The titanium alloy ingot is heat treated at 800℃ for 5-10min, then hot rolled, and the total deformation of each pass is controlled to be 75-85%, and a hot rolled plate is obtained; (8) The hot rolled plate is polished to control the roughness Ra1.6 or more, and the cold rolling deformation is controlled to be 60-80%, and the deformation of single cold rolling treatment is 0.5-2%, and a cold rolled plate is obtained.

2. A design and development of high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy as claimed in claim 1, wherein, In step (1), a low elastic modulus medical titanium alloy dataset was created by collecting existing literature, containing 75 different alloy compositions and their corresponding elastic modulus in solid solution state, and taking alloy composition (C i ) as input and elastic modulus (E) as output, introducing XGBoost regression model to establish the relationship E=f(C i ), R 2 value closer to 1 indicates that the model fits the data better, with smaller error and higher accuracy, and R 2 values are all above 0.

95.

3. A design and method of preparation of high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy as claimed in claim 1, wherein, In step (8), the cold rolled plate has a cold rolled alloy phase composition of β+α″ phase, and the β phase accounts for 90-93% and the α″ phase accounts for 7-10% by volume percentage.

4. The method of designing and developing high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy of claim 1, wherein, In step (8), the cold rolled plate is subjected to deformation aging treatment at 350-450℃ for 10-40min in a high-purity Ar gas environment to obtain a finished biomedical titanium alloy plate.

5. A method of designing and preparing high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy as claimed in claim 4, wherein, The phase composition of the deformation aging state alloy of the finished biomedical titanium alloy plate is β+α phase, and the β phase accounts for 95-97% and the α phase accounts for 3-5% by volume percentage.

6. A method of designing and preparing a high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy according to claim 4 or 5, characterized in that, The final properties of the finished plate of biomedical titanium alloy are: tensile strength Rm not less than 800 MPa, elastic modulus E not higher than 45 GPa, elongation At not less than 10%, "strong modulus ratio" not less than 20.0x10 m not less than 775 MPa, elastic modulus E not higher than 45 GPa, elongation At not less than 10%, "strong modulus ratio" not less than 20.0x10 -3 .

7. The method of design and preparation of high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy as claimed in claim 1, wherein, In step (8), the cold rolled plate is subjected to solid solution treatment at 750-850℃ for 1-1.5h in a high-purity Ar gas environment and then water cooled to room temperature, which is used to verify the phase composition and elastic modulus of the titanium alloy.

8. The method of designing and preparing high strength low modulus Ti-Mo-Nb-Zr-Sn biomedical titanium alloy of claim 7, wherein, The solid solution state alloy of the cold rolled plate is a full β grain structure, and the grain size is 30-50μm.

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