Biomedical titanium alloy
Biomedical materials refer to materials that interact with biological systems to diagnose, treat, repair or replace tissues, organs or enhance their functions in the body. It can be divided into medical metal materials, medical polymer materials, medical ceramic materials, etc. Among them, medical metal materials account for a large proportion, especially orthopedic products and cardiovascular and cerebrovascular products.
Because titanium is close to human bones, it has good biocompatibility to human tissues, no toxic side effects, and has incomparable advantages over other materials, so medical titanium has been widely used in the medical field.
Biocompatibility: Minimal biological reaction with the human body, non-toxic and non-magnetic, as a human implant, it has no toxic and side effects to the human body.
Mechanical properties: high strength, low elastic modulus, which not only meets the mechanical requirements, but also is similar to the elastic modulus of human natural bone, which can reduce the stress shielding effect and is more conducive to the growth and healing of human bone.
Corrosion resistance: Titanium alloy is a biologically inert material, which has intentional corrosion resistance in the physiological environment of the human body, and does not pollute the physiological environment of the human body.
Light weight: The density of general titanium alloy is only 56% of that of stainless steel, which greatly reduces the load on the human body after implantation.
Development History of Biomedical Titanium Alloys
Metal materials are the earliest traditional materials used for wound repair and orthopedic treatment in the history of human biomedicine. Since the 1930s, CoCr alloy and stainless steel have been used in the medical field and become the current traditional medical metal materials; in the 1940s, biomedical titanium with better performance was studied and its clinical feasibility was proved. Biomedical titanium alloys have gone through three processes: pure titanium and Ti-6Al-4V titanium alloys, improved titanium alloys, and low modulus beta titanium alloys:
1950-1980: Pure titanium was first used in the field of biomedicine, confirming good biocompatibility. Ti6Al4V is widely used in surgical repair or replacement materials.
1980-1990: It was confirmed that V and Al are elements with toxic and side effects to the organism; the second-generation improved new medical titanium alloy was developed by replacing V with Nb and Fe.
1990-present: In the early 1990s, the first β-titanium alloy Ti13Nb13Zr with better biocompatibility and lower elastic modulus was developed, and the development and use of biomedical β-titanium alloys with excellent properties have been opened since then.
Domestic research status and problems
my country started the research and application of medical titanium alloy materials in the 1970s. The Metal Research Institute has developed the first near-α type new medical titanium alloy TAMZ (Ti-2.5Al-2.5Mo-2.5Zr) with my country's independent intellectual property rights for the first time in China, and its comprehensive performance is comparable to that of Ti-6Al-7Nb.
In 2005, Northwest Institute of Nonferrous Metals developed two new high-strength and low-modulus near-beta medical titanium alloys, TiZrMoNb (TLE) and Ti Zr SnMo Nb (TLM). The Institute of Metals, Chinese Academy of Sciences has also developed a new low modulus near β-type titanium alloy Ti-24Nb-4Zr-7.6Sn (Ti 2448). In addition, Beijing Nonferrous Metals Institute, Harbin Institute of Technology, Northeastern University, Tianjin University and other units are also carrying out the application of new β-type titanium alloys and related basic research.
Based on my country's national conditions, a large country with a population of about 1.3 billion and 60 million disabled people, and my country is entering an aging society, it is necessary to provide a large number of high-quality biomedical materials and devices for clinical diagnosis and treatment. However, the research on medical implants in my country started late. At present, nearly half of artificial joints need to be imported, and more than 90% of dental implants and some high-end implants are imported products, which are very expensive and difficult for ordinary working-class people. bear. Therefore, the development of novel implantable titanium alloys with no toxicity, low elastic modulus and low price is a worthy research topic.
Classification and properties of biomedical titanium alloys
Biomedical titanium alloys can be divided into three types: α-type, α+β-type and β-type titanium alloys according to the type of material microstructure. At present, the materials widely used in clinic are still mainly pure titanium and Ti-6Al-4V alloy, but β-type titanium alloy has become a research hotspot in this field due to its lower elastic modulus and better biocompatibility. Biomedical titanium alloys with promising applications.
Table 1 shows the mechanical properties of various biomedical titanium alloys. Figure 1 shows a comparison of the elastic moduli of various biomedical alloys and the elastic moduli of human bone. It can be seen that the elastic modulus of the second generation of biomedical titanium alloys is significantly lower than that of the first generation, and the Nb content in the alloy design tends to increase, and they are all β-type titanium alloys, Ti-35Nb-7Zr-5Ta and Ti-29Nb- 13Ta-7.1Zr alloy has the lowest elastic modulus of 55MPa, which is closest to that of human bone. Therefore, the development of biomedical β-type titanium alloys with lower elastic modulus has become a research hotspot in this field. At present, the most widely studied biomedical superelastic β-titanium alloys at home and abroad are Ti-Nb superelastic β-titanium alloys.
Commonly used biomedical beta titanium alloys
In recent years, the research and development of new β-type titanium alloys are mainly Ti-Nb series, Ti-Mo series, Ti-Zr series and Ti-Ta series alloys. (Elements such as V, Al, Ni, Cr and other elements that are harmful to the human body are gradually replaced by non-toxic elements such as Nb, Zr, Ta, Sn, Pt, Mo and other non-toxic elements with good biocompatibility) Some medical low-modulus β Type titanium alloy as shown in the figure below. Compared with other β-titanium alloys, the elastic modulus of Ti-Nb alloys is lower, which is closer to the elastic modulus of human bone, and does not contain toxic elements Al and V, so it is suitable for medical metal materials. many.
Application examples
The excellent biomedical properties of biomedical titanium alloys make it widely used as follows
