Journal
INTERMETALLICS
Volume 131, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.intermet.2021.107114
Keywords
Shape memory alloy; NiTi; Surface nano-crystallization; Ultrasonic shot peening; Functional properties; Aging treatment
Categories
Funding
- National Key R&D Program of China [2018YFB1105100]
- National Natural Science Foundation of China (NSFC) [51905310]
- Shandong Provincial Natural Science Foundation, China [ZR2018QEM001]
- Natural Science Foundation of Jiangsu Province [BK20180231]
- Key Research and Development Program of Shandong Province [2019GGX104065]
- Young Scholars Program of Shandong University [2018WLJH24]
- Foundation of Key Laboratory of Applied Technology of Sophisticated Analytical Instruments of Shandong Province [201806]
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The study proposed a method to improve the functional stability of Ni-rich NiTi alloys through ultrasonic shot peening and low-temperature aging treatment, which can achieve a homogeneous distribution of Ni4Ti3 nanoprecipitates in the sample and strengthen the NiTi matrix.
In this work, we proposed a process to improve the functional stability of Ni-rich NiTi alloys, which combines surface nano-crystallization by means of ultrasonic shot peening and subsequent low-temperature (523 K) aging treatment. The as-annealed coarse-grained NiTi plates were fist subjected to ultrasonic shot peening, which generates nano-grains at the surface region, and introduces dislocation networks in the interior of the NiTi sample. Both the grain boundaries and the dislocations could serve as the heterogenous nucleation sites for Ni4Ti3 nanoprecipitates during subsequent low-temperature aging treatment. Therefore, with the presence of nano-grains and dislocation networks, a homogeneous distribution of Ni4Ti3 nanoprecipitates in the sample is expected, which will strengthen largely the NiTi matrix and resist the plastic activities during the repetitive martensitic transformation. As a result, the improved stability during cyclic superelastic loading is achieved.
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