Microstructure development of quaternary alloy for medical technology

Shape memory alloys are currently established in many different sectors. One of the largest markets is medical technology. The most researched alloy is the binary NITINOL, consisting of almost equivalent proportions of nickel and titanium. The excellent pseudoelastic properties have revolutionised cardiovascular medical technology. Another elementary field of application in medical technology is endodontics.

Ingpuls, in cooperation with Ingpuls Medical, has succeeded in developing a quaternary alloy (MED2) and making it industrially usable for endodontic applications. This system is optimally adapted to the properties and requirements of the doctors using it. The basis of MED2 is a NiTiCu alloy, known for small hysteresis and high functional fatigue in actuator applications.

Medical alloys that are sold commercially have the highest demands on chemical, mechanical, thermal, and microstructural properties. To meet these requirements, a scientific basis was created by metallurgical investigations on the reaction of NiTiCu melts with graphite crucibles. To meet these requirements, the thermodynamic crucible reaction far from equilibrium was investigated for MED2. From the results, it was possible to develop a formula that enables the relationship between the casting condition and the final processed material to be established, considering the proportions of impurities due to carbon and oxygen.

Finally, the microstructural development during the processing of state-of-the-art quaternary alloys is presented. A processing route for MED2 in mass production was developed. The thermomechanical treatment in combination with specifically adjusted recrystallisation processes is decisive for this.