Studies of selected mechanical properties of nitinol – shape memory alloy

Because of their specific properties, shape memory alloys are applied in many domains. The investigations were conducted on nitinol alloy in the form of 3,1 mm diameter wire, whose Af temperature as stated by the manufacturer is Af =65oC. The wire was stretched in a strainhard ened state and after annealing at 500oC. The influence of different heat treatments on the engineering stress – strain curve was investigated. Some samples were relieved and again loaded during tensile test. The plotted curves reflect the transformations that occur in alloy microstructure in high-temperature state (austenite) and low-temperature state (martensite).