Mechanical and Microstructural Characterization of Porous NiTi Shape Memory Alloys

A novel approach in determining the transition temperatures of NiTi shape memory alloys was investigated and compared with conventional techniques. The technique is based on microthemal analysis using a scanning thermal microscope (SThM). In particular, this method has the potential to allow the transformation temperatures of thin films to be investigated in situ. Thin film shape memory alloys have potential applications, such as microactuators, where conventional analysis techniques are either not directly applicable to such samples or are difficult to perform.

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Sintering and Morphology of Porous Structure in NiTi Shape Memory Alloys for Biomedical Applications

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.570.87 ◽

2012 ◽

Vol 570 ◽

pp. 87-95 ◽

Cited By ~ 3

Author(s):

Irfan Haider Abidi ◽

Fazal Ahmad Khalid

Keyword(s):

Elastic Modulus ◽

Shape Memory Alloys ◽

Porous Structure ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Biomedical Implants ◽

Recoverable Strain ◽

Porous Niti ◽

Niti Shape Memory Alloys

The combination of attractive properties of porous NiTi shape memory alloys like high recoverable strain due to superelasticity and shape memory effect, good corrosion resistance, improved biocompatibilty, low density and stiffness along with its porous structure similar to that of bone make them best materials for biomedical implants. In current study porous NiTi SMAs have been fabricated successfully by space holder technique via pressureless sintering using NaCl powder as a spacer. Various volume fractions of NaCl powders have been involved to study their effect on the pore characteristics as well as on mechanical properties of foam. Porous NiTi with average porosity in the range of 44.3%-63.5% have been fabricated having average pore size 419µm which were very appropriate for various biomedical implants. Porous NiTi SMAs exhibited superelasticity at room temperature and shape memory effect was also determined. Maximum recoverable strain of 6.79% was demonstrated by the porous NiTi alloy with 44.3% porosity and it was diminishing with increasing porosity. Compression strength and elastic modulus have shown a decreasing trend with increasing porosity content. Elastic modulus of porous NiTi extends from 1.38 to 5.42GPa depending upon the pore volume which was very much comparable to that of various kinds of bones.

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Microstructural Characterization and Mechanical Behavior of NiTi Shape Memory Alloys Ultrasonic Joints Using Cu Interlayer

Materials ◽

10.3390/ma11101830 ◽

2018 ◽

Vol 11 (10) ◽

pp. 1830 ◽

Cited By ~ 12

Author(s):

Wei Zhang ◽

Sansan Ao ◽

Joao Oliveira ◽

Zhi Zeng ◽

Yifei Huang ◽

...

Keyword(s):

Shape Memory Alloys ◽

Mechanical Behavior ◽

Shape Memory ◽

Energy Levels ◽

Tensile Load ◽

Functional Materials ◽

Microstructural Characterization ◽

Fusion Welding ◽

Niti Shape Memory Alloys ◽

Cu Interlayer

NiTi shape memory alloys (SMAs) are a class of functional materials which can be significantly deformed and recover their original shape via a reversible martensitic phase transformation. Developing effective joining techniques can expand the application of SMAs in the medical and engineering fields. In this study, ultrasonic spot welding (USW), a solid-state joining technique, was used to join NiTi sheets using a Cu interlayer in between the two joining sheets. The influence of USW process on the microstructural characteristics and mechanical behavior of the NiTi joints was investigated. Compared with conventional fusion welding techniques, no intermetallic compounds formed in the joints, which is extreme importance for this particular class of alloys. The joining mechanisms involve a combination of shear plastic deformation, mechanical interlocking and formation of micro-welds. A better bonding interface was obtained with higher welding energy levels, which contributed to a higher tensile load. An interfacial fracture mode occurred and the fracture surfaces exhibited both brittle and ductile-like characteristics with the existence of tear ridges and dimples. The fracture initiated at the weak region of the joint border and then propagated through it, leading to tearing of Cu foil at the fracture interface.

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Electrochemical Stability of Orthopedic Porous NiTi Shape Memory Alloys Treated by Different Surface Modification Techniques

Journal of The Electrochemical Society ◽

10.1149/1.3110945 ◽

2009 ◽

Vol 156 (6) ◽

pp. C187 ◽

Cited By ~ 9

Author(s):

Shuilin Wu ◽

Xiangmei Liu ◽

Tao Hu ◽

Jiang Jiang ◽

Paul K. Chu ◽

...

Keyword(s):

Surface Modification ◽

Shape Memory Alloys ◽

Shape Memory ◽

Electrochemical Stability ◽

Porous Niti ◽

Surface Modification Techniques ◽

Niti Shape Memory Alloys

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Microstructural characterization of shape memory alloys on the atomic scale

TMS 2014: 143rd Annual Meeting & Exhibition ◽

10.1007/978-3-319-48237-8_33 ◽

2014 ◽

pp. 249-256

Author(s):

Christoph Begau ◽

Alexander Hartmaier

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Microstructural Characterization ◽

Atomic Scale

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Alloying effect on K-shell fluorescence parameters of porous NiTi shape memory alloys

Journal of Electron Spectroscopy and Related Phenomena ◽

10.1016/j.elspec.2014.01.002 ◽

2014 ◽

Vol 192 ◽

pp. 55-60 ◽

Cited By ~ 9

Author(s):

E. Cengiz ◽

O.M. Ozkendir ◽

M. Kaya ◽

E. Tirasoglu ◽

I.H. Karahan ◽

...

Keyword(s):

Shape Memory Alloys ◽

Shape Memory ◽

Alloying Effect ◽

Fluorescence Parameters ◽

Porous Niti ◽

Niti Shape Memory Alloys

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In Situ Structural Characterization of Laser Welded NiTi Shape Memory Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.738-739.338 ◽

2013 ◽

Vol 738-739 ◽

pp. 338-343 ◽

Cited By ~ 2

Author(s):

Francisco Manuel Braz Fernandes ◽

Karimbi Koosappa Mahesh ◽

Corneliu Marius Crăciunescu ◽

João Pedro Oliveira ◽

Norbert Schell ◽

...

Keyword(s):

Mechanical Properties ◽

Synchrotron Radiation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Mechanical Behaviour ◽

State Of The Art ◽

Structural Characteristics ◽

Niti Shape Memory Alloys

The demand of emerging joining techniques for shape memory alloys (SMA) has become of great importance, as their functional properties, namely shape memory effect (SME) and superelasticity (SE) present unique solutions for state-of-the-art applications. Literature shows that significant efforts have been conducted on laser welding of these alloys, although very limited results concerning mechanical properties are repeatedly achieved. A better understanding of the mechanical behaviour of these welded joints may be got through a detailed analysis of the structural characteristics of the material from the base metal to the weld bead. Such studies have been carried out on a series of Ni-rich Ni-Ti SMA laser welded plates using synchrotron radiation.

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