It is one of the metals with the best known biological affinity. Since 1940s,
titanium and titanium alloys have been gradually applied in clinical medicine. In 1951, bone plates and screws were made of pure titanium. In the mid 1970s, titanium and titanium alloys began to be widely used in medicine, becoming one of the most promising medical materials.
Titanium and titanium alloys are currently used in orthopedics, especially for limb and skull reconstruction, for a variety of internal fixation devices for fractures, artificial joints, cranium and dura, artificial heart valves, teeth, gums, support rings and crowns.
The density of titanium and titanium alloy is close to the hard tissue of human body, and its biocompatibility, corrosion resistance and fatigue resistance are better than stainless steel and cobalt alloy, so it is the best metal medical materials at present. The affinity between titanium and titanium alloy and human body is derived from the ability of inducing deposition of calcium and phosphorus ions in body fluid to generate apatite by dense titanium oxide (TiO2) passivation film on its surface after implantation, showing certain biological activity and bone-binding ability, which is especially suitable for bone implantation.
Titanium and titanium alloy disadvantage is low hardness, poor wear resistance. If wear occurs, the oxide film will be damaged first, and then the corrosion products of worn particles will enter human tissues, especially the toxic vanadium (V) contained in Ti-6A1-4V alloy, which can lead to the failure of implants. In order to improve the wear resistance of titanium and titanium alloy, the surface of titanium and titanium alloy products can be treated by ion ammoniation or ion implantation technology at high temperature to enhance the wear resistance of the surface. In recent years, some new titanium alloys (mainly β type alloys) have been developed, which focus on reducing the elements harmful to human body, such as V and Al, and effectively improve the biocompatibility of titanium alloys.
In the future, the types of medical metal materials need to be further expanded, and the use cost needs to be further reduced. Therefore, it is very important to develop alloys with high corrosion resistance, high wear resistance, high fatigue strength and high toughness.
