Ductile-Brittle Variation Phenomenon and a Special Transformation-Induced Plasticity Effect in NbTi-NiTi Composite
Abstract
In order to study the transformation-induced plasticity (TRIP) effect in a NiTi shape-memory alloy composite, an in situ NbTi-NiTi composite was prepared by vacuum arc melting, hot forging and wire drawing. An unusual ductile-brittle variation phenomenon was observed by means of a series of tensile tests. The composite was brittle in the absence of transformation at 200 °C, and the fracture strain was about 2%. With lowering the tensile temperature, the composite became ductile when stress-induced martensitic transformation occurred, and the elongation increased to about 18% (a ninefold increase) during tensile test at room temperature. This ductile-brittle variation phenomenon indicates that the stress-induced martensitic transformation of NiTi alloy helps to improve the ductility of the composite, which is just the exhibition of TRIP effect in the NbTi-NiTi composite. Different from conventional TRIP steels, the TRIP behavior in NiTi induces only an increase in the elongation, but not any increase in fracture strength.
- Publication:
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Journal of Materials Engineering and Performance
- Pub Date:
- January 2020
- DOI:
- 10.1007/s11665-020-04591-6
- Bibcode:
- 2020JMEP...29..296J
- Keywords:
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- NiTi-NbTi composite;
- shape-memory alloy;
- stress-induced martensitic transformation;
- transformation-induced plasticity (TRIP)