Abstract
Ageing treatments were performed on Ti‐50.53 at.% Ni shape memory alloy corrugated gasket (SMA‐CG) units. The results of phase transition temperature, shape‐setting, compression‐resilience performance, and the shape memory effect (SME) of NiTi corrugated units were investigated. The experimental results show that high austenite finish temperatures could be achieved at 500°C and at 400°C aged for a long time, while the martensite finish temperatures were basically above room temperature. The peak value of the austenite finish temperature was found to be 500°C. The shape‐setting result was better with the increase of ageing temperature and ageing time. It was stable when units were constrain‐treated at 500°C and the ageing time was longer than 30 min. As the strain increases, the resilience rate of the unit decreased rapidly. The resilience rate decreased with the ageing process. Most of the aged units exhibited good SME when the maximum strain was less than 40%. There was the best recoverability when the ageing treatment was performed at 500°C for 60 min.
Highlights
In the process industry, it is important for a gasket to adapt to flange irregularities and to any dimensional changes of the flange system caused by temperature changes during operation
In the differential scanning calorimetry (DSC) curve, when the specimen was cooling down, Ms and Mf were defined as martensite phase transition start and finish temperature, respectively
While the specimen was heated up, As and Af were defined as austenite phase transition start and finish temperature, respectively. e hysteresis (As–Ms) can be measured by taking the temperature different between the forward and reverse transformation
Summary
It is important for a gasket to adapt to flange irregularities and to any dimensional changes of the flange system caused by temperature changes during operation. Ageing or annealing of the SMA subsequent to the shape-setting operation is one way to change the material properties of the SMA including the yield strengths and the phase transformation temperature. Our focus was to optimize the ageing treatment parameters for fixing the NiTi corrugated gasket unit to achieve the best result of shape-setting. Shape-set ageing treatments were performed on the sheets, together with the molds, at temperatures of 300, 400, and 500°C for 10, 30, and 60 min in a tube furnace (BTF1400C, China), followed by air cooling. Cooling and heating rate during thermal cycling was 10°C/min
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