scholarly journals Determination of Elastic and Dissipative Energy Contributions to Martensitic Phase Transformation in Shape Memory Alloys

10.5772/51511 ◽  
2013 ◽  
Author(s):  
Dezso L. ◽  
Lajos Daroczi ◽  
Tarek Y.
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation

Suppression of Martensitic Phase Transformation, Shape Memory and High Damping by Ion Implantation in Ni-Ti Thin Films

2006 ◽  
Vol 319 ◽  
pp. 17-24
Author(s):  
Rolf Gotthardt
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Memory Effect ◽  
Ion Irradiation ◽  
Amorphous State ◽  
Amorphous Layer ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Damping Capacity

The shape memory effect and the high damping in shape memory alloys are based on the martensitic phase transformation, which takes place essentially without diffusion and any change of order have an influence on its side effects: the memory effect, the superelasticity and the high damping capacity of the martensitic phase. A new method to control the performance of shape memory alloys is presented, which is based on selective modification of specified parts of working components. In this research, ion irradiation has been used to introduce locally disorder into a crystal or even amorphise it. A pre-deformed Ni-Ti, 6μm thin film in its martensitic state has been irradiated with Ni-ions of energy of 5 MeV up to a dose of 1016 ions/cm2. By this treatment, a 2μm thin surface layer has been finally transformed into an amorphous state, in which the martensitic transformation is suppressed. During heating the underlying non-modified layer is contracting and an out-of-plane movement is observed. The amorphous layer is elastically deformed and its energy is used during cooling to bring the film in its original shape. In this way, a reversible movement of the film is created. This new technique not only allows us to design new types of micro-actuators, but also to influence locally the high damping, which can be of great importance for micro-engineering applications.

scholarly journals Brief Overview on Nitinol as Biomaterial

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Abdul Wadood
Keyword(s):  
Phase Transformation ◽  
Research And Development ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Martensitic Phase ◽  
Martensitic Phase Transformation ◽  
Recoverable Strain

Shape memory alloys remember their shape due to thermoelastic martensitic phase transformation. These alloys have advantages in terms of large recoverable strain and these alloys can exert continuous force during use. Equiatomic NiTi, also known as nitinol, has a great potential for use as a biomaterial as compared to other conventional materials due to its shape memory and superelastic properties. In this paper, an overview of recent research and development related to NiTi based shape memory alloys is presented. Applications and uses of NiTi based shape memory alloys as biomaterials are discussed. Biocompatibility issues of nitinol and researchers’ approach to overcome this problem are also briefly discussed.

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