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.

Evaluation of Blister Behavior for U10Mo Mini Fuel Plates With Cold Rolled Foils

2012 ◽  
Author(s):  
Hakan Ozaltun ◽  
Samuel J. Miller
Keyword(s):  
Cold Rolling ◽  
Thermal Cycling ◽  
Cold Work ◽  
Rolling Process ◽  
Foil Thickness ◽  
Rolled Plate ◽  
Stress Profile ◽  
Wide Range ◽  
Threshold Temperatures ◽  
Cold Rolled

This article aims to provide possible mechanical causes for the lowered blister temperatures of RERTR-12 and AFIP-4 fuel plates. Recent experimental investigations to determine the blister threshold temperatures have indicated lower thresholds for similar plates with comparable burn-up histories. Measured blister temperatures of roughly 100 °C lower compared to the previously tested plates may not be satisfactory for some plates. The primary differences between recent experiments and previous tests are: (1) An aggressive cold work process involving large thickness reduction ratios without normalization or full annealing (2) Subjecting the plates to a thermal cycling process prior to irradiation, and finally (3) A primarily frontal neutron flux as opposed to a transverse flux profile. It is believed that the stress field has implications to blister behavior. To investigate this claim, the stress-strain states for the fabrication procedure were evaluated. First, the residual stress profile caused by the cold rolling process was calculated. Modeling of the cold rolling process has shown confirmation of residual stresses of considerable magnitude and the existence of stress gradients with respect to foil thickness prior to the HIP process. Once calculated, these stress profiles were used as an initial condition for the fabrication process. Due to the variation in stress fields depending on location at which a foil is cut from the cold rolled plate, three representative regions were selected and implemented in the HIP simulation. Variation in stresses, depending on location of the cold rolled plate as well and variation in the through-thickness, results in a wide range of mechanical stress states. This suggests that inhomogeneous irradiation and thermal cycling behavior will result from the use of cold rolled foils. Additionally, these results suggest that there will be fundamental differences in fuel plate behavior observed between plates fabricated with cold rolled foils versus hot rolled and fully annealed foils.

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.

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.

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