With the vigorous development and major breakthroughs in biotechnology,the demand for biomedical titanium alloys has been rapidly increasing.However,due to the pathogenic nature of V and Al elements present in widely used biomedical titanium alloys such as TC4 and TC4ELI,the research and development of new biomedical titanium alloys holds significant practical importance and boasts vast market prospects in China.This article briefly outlines the classification,basic properties,and application fundamentals of biomedical titanium alloys;points out the development trends in the medical field;and reviews the basic processing and preparation methods as well as performance evaluation methods for newβtitanium alloys.

Biomedical titanium alloy materials refer specifically to a class of functional structural materials used in biomedical engineering,specifically for the production and manufacture of surgical implants and orthopedic devices.The production and preparation of titanium alloy processed materials involve fields such as metallurgy,pressure processing,composite materials,and chemical engineering,and are recognized globally as high-tech products.Titanium and titanium alloys have gradually entered the civilian consumption sector from the aerospace,aviation,and defense military industries.Products such as implants and medical devices in the medical and healthcare industry,titanium golf clubs in the sports and leisure industry,as well as titanium eyeglass frames,titanium watches,titanium bicycles,and other products,have led to a continuously increasing demand for titanium processed materials.With the vigorous development and major breakthroughs in biotechnology,the biomedical metal materials and their products industry will develop into a pillar industry of the world economy.Among them,titanium and its alloys,with their excellent comprehensive properties such as light weight,low elastic modulus,non-toxic and non-magnetic properties,corrosion resistance,high strength,and good toughness,have also seen rapid and steady growth in demand in recent years.At the same time,as titanium alloys begin to enter fields such as plastic surgery,new potential market demands have emerged,and the titanium alloy market will experience even faster growth in the future.

1 Research progress of medical titanium alloys

1.1 Classification of medical titanium alloys

Titanium alloys can be classified into three types according to their material microstructure:α-type,α+β-type,andβ-type titanium alloys.

1.2 Development trend of medical titanium alloys

Research has found that relevant scholars both domestically and internationally unanimously agree that the development of medical titanium alloys has gone through three landmark stages.The first stage is represented by pure titanium and Ti-6Al-4V alloy;the second stage is represented by newα+βtype alloys such as Ti-5Al-2.5Fe and Ti-6Al-7Nb;the third stage is primarily focused on the development and research ofβ-titanium alloys with better biocompatibility and lower elastic modulus.Ideal biomedical titanium alloy materials must meet the following conditions:good biocompatibility,low elastic modulus,low density,good corrosion resistance,non-toxicity,high yield strength,long fatigue life,high plasticity at room temperature,easy to form,easy to cast,etc.Currently,Ti-6Al-4V and Ti-6Al-4VELI are important alloys widely used in implant materials.It has been reported that the element V can cause malignant tissue reactions,potentially leading to toxic side effects on the human body,while Al can cause osteoporosis and mental disorders.To address this issue,current biomaterial scientists are dedicated to exploring and researching new biomedical titanium alloy materials without V and Al.Before that,it is necessary to clarify which alloy elements are suitable to add that are both non-toxic and comply with biocompatibility principles.Some studies have found thatβ-titanium alloys containing non-toxic elements such as molybdenum,niobium,tantalum,and zirconium have higher contents ofβ-stabilizing elements.Compared toα+βtype titanium alloys,they have lower elastic modulus(E=55~80GPa)and better shear properties and toughness,making them more suitable for implantation into the human body as implants.

2.Application of titanium alloy

2.1 Medical fundamentals of titanium alloys

2.2 Medical and orthopedic applications of titanium alloys

With the development and research of titanium alloys,the increase in titanium material varieties,and the reduction in prices,the application of titanium in civil industry has doubled.The China Food and Drug Administration(CFDA)divides medical devices into three levels according to their safety,from high to low,and supervises and manages them by three levels of government.Implants made of titanium and titanium alloy materials belong to the third category of medical devices and are classified as high-value consumables.Sub-sectors with a market share of more than 5%include six major segments:in vitro diagnostics,cardiac,diagnostic imaging,orthopedics,ophthalmology,and plastic surgery.Among them,in vitro diagnostics,orthopedics,and cardiac intervention are the fastest-growing high-value consumables in China.The application of biomedical titanium and its alloy materials has gone through three landmark stages:In the early 1950s,during the initial application stage,commercially pure titanium was first used to manufacture bone plates,screws,intramedullary nails,and hip joints in the UK and the US.The Swiss company Mathys also used Ti-6A1-7Nb alloy to manufacture unreamed locking intramedullary nail systems(including tibial,humeral,and femoral)and hollow screws for the treatment of femoral neck fractures.Porous Ni-Ti(PNT)alloy bioactive materials are used to manufacture cervical and lumbar interbody fusion devices.The Canadian company BIORTHEX has developed a patent material called ACTIPORE®made of porous Ni-Ti alloy for the manufacture of cervical and lumbar interbody fusion devices used in the treatment of spinal injuries in orthopedics.The newβtitanium alloy can serve multiple purposes in orthopedics,dentistry,and vascular intervention.The orthopedic medical device industry accounts for 9%of the global medical device market share and is still growing rapidly.The orthopedic medical device market is mainly divided into four areas:trauma,joints,spine,and others.Among them,trauma is currently the only segment that is not dominated by foreign companies in terms of market share,mainly due to the low technological content of products in this field,which are easy to imitate,and the surgical difficulty is relatively low,allowing many second-and third-tier hospitals to perform the procedures.Foreign companies cannot fully cover this segment.Trauma products can be divided into internal fixation and external fixation devices.Internal fixation trauma products include intramedullary nails,bone plates,and screws.In 2012,the domestic orthopedic market accounted for 34%of trauma,28%of joints,20%of spine,and 18%of other segments.Large joints belong to high-end medical devices with high technical barriers.Currently,mainstream hospitals mainly choose imported orthopedic materials.There is still a gap between domestic and imported products in terms of technology,design,research and development,materials,and surface treatment processes.Artificial joints are mainly divided into artificial knees,hips,elbows,shoulders,fingers,and toes,among which the most important joint replacements include hip and knee joints,which together account for more than 95%of the global joint replacement market.Spinal implant devices include thoracolumbar screw plate systems,cervical screw plate systems,and fusion device systems.Among them,the intervertebral fusion device system is primarily used for the treatment of disc replacement and is the most significant segment,accounting for approximately half of the entire spinal implant market.

The superior properties of titanium alloys have contributed to their leading position in the medical field.The material design and preparation technology of titanium alloys have developed rapidly with the breakthroughs in biotechnology and the substantial demand for medical applications.Currently,the medical titanium alloys produced are mainlyα+βtitanium alloys.In terms of preparation technology,TC4(TC4 ELI)currently occupies the majority of the market share.Due to its advantages in biocompatibility and mechanical compatibility,βtitanium alloy has become a research hotspot for new medical titanium alloys and represents the most promising technology in the field of medical implants.In the future,the production technology of titanium alloys should develop towards low modulus,high strength,and good biocompatibility and mechanical compatibility.From the perspective of development trends,βtitanium alloy will become the direction for future development and the mainstream in the medical titanium alloy market.