Functionally graded niti shape memory alloys by ageing and partial annealing
| dc.contributor.author | Muhammad Naqib Nashrudin | |
| dc.date.accessioned | 2021-11-11T00:52:14Z | |
| dc.date.available | 2021-11-11T00:52:14Z | |
| dc.date.issued | 2018-07-01 | |
| dc.description.abstract | A shape memory behavior of NiTi alloy delivers constant forces when load is applied on it. Thus, the limitation for any progressive or intermediate state of control makes the alloy to function only for discrete action application. To enable a better control in actuation applications, a functionally graded NiTi is created by introducing a gradient heat treatment along the alloy. Recently, few works have been reported on gradient annealing treatment of cold-worked near-equatomic NiTi alloy to produce steeper stress plateau slope while gradient ageing treatment in Ni-rich alloy produces good recovery strain on the reverse transformation. This study explored the effect of partial annealing and ageing treatment of a cold-worked Ti-50.9at%Ni wire towards martensite phase transformation behavior and to create multiple steps of stress plateau NiTi wire by localizing the heat treatment along the wire. Specimen used in this study was a Ti-50.9at%Ni wire with a diameter of 2 mm. The specimens were heated at temperature range of 300℃ to 550℃ for duration of 10, 20, 30 and 60 minutes in argon atmosphere. The thermal martensite phase transformation behavior was characterized by using a differential scanning calorimeter (DSC) and the shape memory deformation behavior was studied by using a universal testing machine (UTM). The experimental work explored a concept of functionally graded NiTi materials. The gradient temperature profile was locally created by CO2 laser along its length. The effective temperature range for gradient profile for functionally graded cold-worked Ti-50.9at%Ni was determined at 400℃ - 525℃ at different duration.Two specimens of wire were tested with same temperature and different duration. It was found that the specimen with different duration in a single wire produced higher stress interval. The temperatures are 400℃ for 10 min, 475℃ for 30 minutes and 525℃ for 20 minutes. During tension, the localized heat treated with different duration exhibited forward stress interval which is 301 MPa and reverse stress interval of 265 MPa. The deformation yielding around 10% transformation strain and the residual strain is 1%. The localized laser heat treatment method executes a positive result in creating multiple steps of stress plateau of functionally graded behavior of NiTi alloy. | en_US |
| dc.identifier.uri | http://hdl.handle.net/123456789/14360 | |
| dc.language.iso | en | en_US |
| dc.title | Functionally graded niti shape memory alloys by ageing and partial annealing | en_US |
| dc.type | Thesis | en_US |
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