Test Method for Determination of Transformation Temperature of Nickel-Titanium Shape Memory Alloys by Bend and Free Recovery

2016 ◽  
Author(s):  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Transformation Temperature ◽  
Nickel Titanium ◽  
Test Method

scholarly journals Notes on the experimental measurement of fracture toughness of shape memory alloys

2019 ◽  
Vol 31 (3) ◽  
pp. 475-483 ◽  
Author(s):  
Jasdeep Makkar ◽  
Theocharis Baxevanis
Keyword(s):  
Fracture Toughness ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Measurement Accuracy ◽  
Test Method ◽  
Specimen Thickness ◽  
Resistance Curve ◽  
Ductile Materials ◽  
Induced Changes

A mechanics-aided test method for measuring the fracture toughness of shape memory alloys, the deformation/failure response of which violates basic assumptions of ASTM standards for measuring fracture toughness in conventional ductile materials, has been recently proposed. The proposed methodology relies on the resistance curve format of ASTM standards, but differs from it in the determination of the elastic part of the J value, for both stationary and advancing cracks, in an effort to accommodate the transformation/orientation-induced changes in the apparent elastic properties. This article discusses the proposed modifications to ASTM standards, that is, the expected degree of improvement in the measurement accuracy, the need for further ones regarding the uncertainty as to where to specify the fracture point on the obtained resistance curve, the specimen thickness requirement to ensure a conservative, constraint-independent measurement, and the temperature dependence of the measurements.

The electron beam freeform fabrication of NiTi shape memory alloys. Part I: Microstructure and physical–chemical behavior

2020 ◽  
pp. 146442072097505
Author(s):  
RPM Guimarães ◽  
F Pixner ◽  
G Trimmel ◽  
J Hobisch ◽  
T Rath ◽  
...  
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Nickel Titanium ◽  
Freeform Fabrication ◽  
Austenitic Transformation ◽  
Columnar Grains ◽  
One Step ◽  
Niti Shape Memory Alloys

Nickel–titanium alloys are the most widely used shape memory alloys due to their outstanding shape memory effect and superelasticity. Additive manufacturing has recently emerged in the fabrication of shape memory alloy but despite substantial advances in powder-based techniques, less attention has been focused on wire-based additive manufacturing. This work reports on the preliminary results for the process-related microstructural and phase transformation changes of Ni-rich nickel–titanium alloy additively manufactured by wire-based electron beam freeform fabrication. To study the feasibility of the process, a simple 10-layer stack structure was successfully built and characterized, exhibiting columnar grains and achieving one-step reversible martensitic–austenitic transformation, thus showing the potential of this additive manufacturing technique for processing shape memory alloys.

scholarly journals Crystallographic Attributes of a Shape-Memory Alloy

1999 ◽  
Vol 121 (1) ◽  
pp. 93-97 ◽  
Author(s):  
Kaushik Bhattacharya
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Nickel Titanium ◽  
Potential Applications

Shape-memory Alloys are attractive for many potential applications. In an attempt to provide ideas and guidelines for the development of new shape-memory alloys, this paper reports on a series of investigations that examine the reasons in the crystallography that make (i) shape-memory alloys special amongst martensites and (ii) Nickel-Titanium special among shape-memory alloys.

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