Standard Specification for Wrought Nickel-Titanium Shape Memory Alloys for Medical Devices and Surgical Implants

This specification covers the chemical, physical, mechanical, and metallurgical requirements for wrought nickel-titanium bar, flat rolled products, and tubing containing nominally 54.5 % to 57.0 % nickel and used for the manufacture of medical devices and surgical implants. The material shall be made from ingot made from nickel and titanium with no other intentional alloy additions. The material shall be vacuum or inert atmosphere melted to control metallurgical cleanliness and alloy chemistry. Bar, plate, and tubing shall be supplied as hot finished or cold finished and annealed or heat treated. Surface condition may be oxidized, descaled, pickled, blasted, machined, ground, mechanically polished, or electropolished. Major elements shall be analyzed by direct current plasma spectrometry, atomic absorption, inductively coupled plasma spectrometry, X-ray spectrometer, glow discharge mass spectrometry, or an equivalent method. Carbon shall be measured by combustion and hydrogen shall be measured by inert gas fusion or vacuum hot extraction. Nitrogen and oxygen shall be measured by inert gas fusion. The nickel and titanium contents of nickel-titanium shape memory alloys cannot be measured to a precision required to guarantee shape memory or superelastic properties. Calorimetry or an equivalent thermomechanical test method must be used to assure the alloy formulation in terms of transformation temperature. Mechanical properties of the samples such as tensile strength and elongation shall be determined after annealing.