The effect of severe marforming on shape memory characteristics of a Ti-rich NiTi alloy processed using equal channel angular extrusion

The evolution of the ultrafine structure, obtained at thermal treatment below recrystallization, and its effect onto shape memory characteristics in NiTi alloy was under study. It was shown that low temperature annealing (< 0.5 Tmelt) of the hot rolled NiTi leads to the structure refinement accompanied by the growth in accumulated martensite deformation. It was suggested that this is possible due to the increase of the volume fraction of martensite crystals properly oriented in respect to external stress.

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The dependence of microstructure and mechanical properties of Ti49.0Ni51.0 alloy with the shape memory effect from the initial microstructure in the process of equal channel angular extrusion

Application to Journal. Tambov University Reports. Series: Natural and Technical Sciences ◽

10.20310/1810-0198-2018-23-123p-562-565 ◽

2018 ◽

pp. 562-565

Author(s):

Anna Alexandrovna Churakova ◽

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Dmitry Valerievich Gunderov ◽

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Keyword(s):

Mechanical Properties ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Equal Channel Angular Extrusion ◽

Initial Microstructure ◽

Microstructure And Mechanical Properties ◽

Angular Extrusion

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Shape Memory Characteristics of NiTi Alloy Wire under Various Constrained Stresses

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.567.135 ◽

2012 ◽

Vol 567 ◽

pp. 135-140 ◽

Cited By ~ 1

Author(s):

Yan Feng Li ◽

X.J. Mi ◽

Xiang Qian Yin ◽

H.F. Xie

Keyword(s):

Shape Memory ◽

Annealing Temperature ◽

Volume Fraction ◽

Niti Alloy ◽

Transformation Temperatures ◽

Austenitic Transformation ◽

Heating And Cooling ◽

Recovery Strain ◽

High Annealing ◽

Memory Characteristics

The present research aims to understand the transformation temperatures and recovery strain of NiTi wires during heating and cooling under various constrained stresses. Both constrained stress and annealing temperature have significant effects on the shape memory characteristics. In general, increasing constrained stress causes an increase of the austenitic and martensitic transformation temperatures and a decrease of the recovery strain. This effect can be attributed to that the constrained stress inhibits the austenitic transformation, and thus more volume fraction of the martensite is retained during heating. The high annealing temperature leads to the decrease in the recovery strain.

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Equal Channel Angular Extrusion (ECAE) of Ni-Ti Based Shape Memory Alloy Systems

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.3195 ◽

2007 ◽

Vol 539-543 ◽

pp. 3195-3200

Author(s):

Chin Jye Yu ◽

Chiang Shu Lei ◽

Rabindra Mahapatra ◽

Jeff Sharp ◽

Ibrahim Karaman

Keyword(s):

Shape Memory ◽

Equal Channel Angular Extrusion ◽

Temperature Hysteresis ◽

Scanning Calorimetry ◽

Microstructural Refinement ◽

Transformation Temperatures ◽

Shape Memory Behavior ◽

Transmission Electron ◽

Angular Extrusion ◽

Substructure Formation

In this paper we report the effects of Equal Channel Angular Extrusion (ECAE) processing on the phase transformation characteristics of Ni-Ti based shape memory alloys in terms of transformation temperatures, temperature hysteresis, and microstructural evolution. The ECAE process affects the material’s shape memory behavior via microstructural refinement. Differential Scanning Calorimetry (DSC) and Transmission Electron Microscopy (TEM) were utilized to investigate the effects of microtructural refinement and substructure formation on the shape memory behavior of these alloys. The microstructural refinement was found to have significant influence on the transformation temperatures.

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