Invar-type effect induced by cold-rolling deformation in shape memory alloys

2002 ◽  
Vol 80 (23) ◽  
pp. 4348-4350 ◽  
Author(s):  
R. Kainuma ◽  
J. J. Wang ◽  
T. Omori ◽  
Y. Sutou ◽  
K. Ishida
Keyword(s):  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Rolling Deformation ◽  
Invar Type

A Comparative Study of Structure Formation in Thermomechanically Treated Ti-Ni and Ti-Nb-(Zr, Ta) SMA

2012 ◽  
Vol 706-709 ◽  
pp. 1931-1936 ◽  
Author(s):  
Sergey Prokoshkin ◽  
Vladimir Brailovski ◽  
Karine Inaekyan ◽  
Andrey Korotitskiy ◽  
Sergey Dubinskiy ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Comparative Study ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Structure Formation ◽  
Thermomechanical Treatment ◽  
Functional Properties ◽  
Nanocrystalline Structure ◽  
Technological Factors

The processes of structure formation in Ti-Ni and in Ti-Nb-Zr, Ti-Nb-Ta shape memory alloys (SMA) under thermomechanical treatment (TMT) were studied. The TMT comprised cold rolling with true strains from e=0.25 to 2 and post-deformation annealing. Differences in these processes between two groups of alloys are considered. The main conclusions are as follows: nanostructures created by TMT are useful for radical improvement of the SMA functional properties, and an optimum nanostructure (nanocrystalline structure, nanosubgrained structure or theirmixture) should be selected by taking into account other structural and technological factors.

scholarly journals Superelasticity Evaluation of the Biocompatible Ti-17Nb-6Ta Alloy

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Alaa Keshtta ◽  
Mohamed A.-H. Gepreel
Keyword(s):  
Fracture Surface ◽  
Cold Rolling ◽  
Shape Memory ◽  
Tensile Testing ◽  
Martensite Phase ◽  
Healthcare Applications ◽  
Ti Alloys ◽  
Alloy Microstructure ◽  
Two Phases ◽  
Rolling Deformation

Recently, studying the shape memory effect of the biocompatible Ti alloys takes much attention in the biomedical and healthcare applications. This study concerns about characterizing the superelasticity of the new biocompatible Ti-17Nb-6Ta (TNT) alloy. Microstructure of TNT was observed using optical and confocal microscopes. The alloy consists of two phases: β (predominant phase) and α″ martensite phase. The influence of cold rolling deformation on the microstructure was illustrated in which the martensitic-induced transformation appeared by cold rolling. The alloy is ductile as only the fracture dimples appeared in its fracture surface. Multicyclic loading and deloading tensile testing was applied to TNT specimens (flat and wire shapes) in order to evaluate the superelasticity. A superelastic strain as high as 3.5% was recorded for this TNT alloy. Therefore, TNT alloy has high potential for many biomedical and healthcare applications.

Effect of Cold Rolling on the Damping of As Cast Cu-Al-Mn Shape Memory Alloys

2008 ◽  
Vol 137 ◽  
pp. 155-162 ◽  
Author(s):  
Agnieszka Mielczarek ◽  
Yvonne Wöckel ◽  
Werner Riehemann
Keyword(s):  
Dislocation Density ◽  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Cold Work ◽  
Amplitude Dependence ◽  
Aluminium Content ◽  
Aging Effects ◽  
High Deformation ◽  
Cold Rolled

The ductility of Cu – Al – Mn shape memory alloys at room temperature depends on the aluminium content. High aluminium contents make Cu – Al – Mn very brittle and unsuitable for plastic shaping. Two Cu – Al – Mn shape memory alloys were investigated. The ductile alloy CuAl7.8Mn9.5 (all contents in wt. %) could be easily cold rolled by 86 %. The alloy CuAl12Mn4.3 could be cold rolled by only 12 - 14 %. The amplitude dependence of damping of austenitic specimens increased with increasing degree of cold work, whereas the damping of martensiticaustenitic specimens decreased. These observations can be explained by the creation of stress induced martensite and therefore by new moveable interfaces like phase- and twin boundaries, which contribute to damping. Plastic deformation increases the dislocation density, too. Both the increase of dislocation density and the increase of martensite content can lead to a decrease of damping mainly for high deformation degrees. Same shape memory alloys have shown negligible hardness increase during cold rolling, too. This behaviour, untypical for metals, can be explained by the generation of new martensite and by the fact that the hardness of martensite is smaller than the hardness of austenite. Some aging effects of the specimen after cold rolling, which lead to decrease of damping, were detected. This can be explained by pinning of moveable interfaces by point defects and/or retransformation of martensite into austenite.

Martensitic Transformation and Mechanical Behavior of TiNi Shape Memory Alloys after Severe Plastic Deformation

2006 ◽  
Vol 503-504 ◽  
pp. 419-424
Author(s):  
Koichi Tsuchiya ◽  
M. Inuzuka ◽  
Akihide Hosokawa ◽  
Dacian Tomus ◽  
Hiroyuki Nakayama ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Martensitic Transformation ◽  
Severe Plastic Deformation ◽  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Limited Extent ◽  
Dsc Analysis ◽  
Stress Plateau ◽  
Nanocrystalline And Amorphous

Thermal- and stress-induced martensitic transformation was investigated on TiNi shape memory alloys subjected to severe plastic deformation (SPD) by cold rolling. TEM observation revelaed the sample is a mixture of nanocrystalline and amorphous after 40% cold rolling. DSC analysis suggested that the martensitic transformation was suppressed when the thickness reduction was over 25% reduction. Aging at lower temperatures (573 ~ 673 K, 3.6 ks) restores the phase transformations, but to a limited extent. The stress-strain curves of nanocrystalline/amorphous TiNi are characterized by absence of stress-plateau and small hysteresis.

Functional Properties of Ti-Ni-Based Shape Memory Alloys

2008 ◽  
Vol 59 ◽  
pp. 156-161 ◽  
Author(s):  
I. Khmelevskaya ◽  
Sergey Prokoshkin ◽  
Vladimir Brailovski ◽  
K.E. Inaekyan ◽  
Vincent Demers ◽  
...  
Keyword(s):  
Grain Size ◽  
Cold Rolling ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Functional Properties ◽  
High Pressure Torsion ◽  
Martensitic Transformations ◽  
Critical Temperatures ◽  
Recoverable Strain ◽  
Ultrafine Grained

The main functional properties (FP) of Ti-Ni Shape Memory Alloys (SMA) are their critical temperatures of martensitic transformations, their maximum completely recoverable strain (er,1 max) and maximum recovery stress (sr max). Control of the Ti-Ni-based SMA FP develops by forming well-developed dislocation substructures or ultrafine-grained structures using various modes of thermomechanical treatment (TMT), including severe plastic deformation (SPD). The present work shows that TMT, including SPD, under conditions of high pressure torsion (HPT), equal-channel angular pressing (ECAP) or severe cold rolling followed by post-deformation annealing (PDA), which creates nanocrystalline or submicrocrystalline structures, is more beneficial from SMA FP point of view than does traditional TMT creating well-developed dislocation substructure. ECAP and low-temperature TMT by cold rolling followed by PDA allows formation of submicrocrystalline or nanocrystalline structures with grain size from 20 to 300 nm in bulk, and long-size samples of Ti-50.0; 50.6; 50.7%Ni and Ti-47%Ni-3%Fe alloys. The best combination of FP: sr max =1400 MPa and er,1 max=8%, is reached in Ti-Ni SMA after LTMT with e=1.9 followed by annealing at 400°C which results in nanocrystalline (grain size of 50 to 80 nm) structure formation. Application of ultrafine-grained SMA results in decrease in metal consumption for various medical implants and devices based on shape memory and superelastiсity effects.

Microstructure and thermal expansion properties of invar-type Cu-Zn-Al shape memory alloys

2004 ◽  
Vol 33 (10) ◽  
pp. 1098-1102 ◽  
Author(s):  
J. J. Wang ◽  
T. Omori ◽  
Y. Sutou ◽  
R. Kainuma ◽  
K. Ishida
Keyword(s):  
Thermal Expansion ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Invar Type
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