Adjustment of Aging Temperature for Reaching Superelasticity in Highly Ni-Rich Ti-51.5Ni NiTi Shape Memory Alloy |
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Authors: | M. Karimzadeh M. T. Salehi S. M. Abbasi M. Morakabati |
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Affiliation: | 1. Center of Excellence for High Strength Alloys Technology, Iran University of Science and Technology (IUST), Tehran, Iran;2. Metallic Materials Research Center (MMRC), Maleke Ashtar University of Technology, Tehran, Iran |
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Abstract: | In this research, the effects of aging temperature on the phase transformation, mechanical properties, and superelasticity of Ti–51.5 at.% Ni alloy were investigated. For this purpose, samples were solution annealed and then aged at different temperatures ranging from 300 to 700°C. The results showed that the change of aging temperature has a great influence on the behavior of the alloy. Aging at 300 and 400°C led to the occurrence of the austenite to R phase (A ? R) transformation. By aging at these temperatures, the ultimate tensile strength and elongation did not change significantly compared to the solution annealed sample. Aging at 500 and 600°C led to the appearance of B19′ phase during cooling cycle of differential scanning calorimetry tests. Samples aged at 500 and 600°C showed the best mechanical properties, in comparison with the other aging temperatures. Maximum tensile strength of 1250 MPa and the elongation of 25% were obtained by aging at 500 and 600°C, respectively. Solution-annealed sample showed no superelastic property. Complete superelasticity was observed by aging at 400 and 500°C. The sample aged at 700°C showed the transformation behavior and mechanical properties similar to the solution annealed sample. |
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Keywords: | Aging Deformation Martensitic Mechanical Properties Pseudoelasticity Superelasticity Transformation |
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