Mechanical Spectroscopy of Hyperstabilized Martensites

2012 ◽  
Vol 184 ◽  
pp. 355-360 ◽  
Author(s):  
Sergey Kustov ◽  
R. Santamarta ◽  
E. Cesari ◽  
K. Sapozhnikov ◽  
V. Nikolaev ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Internal Friction ◽  
Essential Role ◽  
Parent Phase ◽  
Martensitic Transformation Temperature ◽  
Mechanical Spectroscopy ◽  
Internal Friction Peak ◽  
Pinning Effect ◽  
The One

The internal friction of the hyperstabilized martensite demonstrates very low values, both above and below the nominal martensitic transformation temperature, due to a pronounced pinning effect. Over a wide temperature range it is comparable with the level of damping in the parent phase. A study of the temperature dependence of the non-linear ultrasonic internal friction and its strain amplitude hysteresis indicates that the diffusion, assisted by dislocations/interfaces, is quite pronounced and in Ni-Fe-Ga and Cu-Al-Be alloys it operates at temperatures around 20 K. The renucleation of the lamellar parent phase during the reverse martensitic transformation close to 600 K is accompanied by an internal friction peak which demonstrates a substantial transitory contribution. After renucleation of the parent phase the samples recover a conventional martensitic transformation with the internal friction level in the martensite comparable to the one in non-stabilized samples. Observations of a relaxation peak in the parent phase of different alloys for temperatures just below the renucleation stage of the reverse transformation point to the essential role of diffusion in the nucleation of the parent phase in hyperstabilized martensites.

HYPERSTABILIZATION OF MARTENSITES

2012 ◽  
Vol 05 (01) ◽  
pp. 1250005 ◽  
Author(s):  
SERGEY KUSTOV ◽  
RUBEN SANTAMARTA ◽  
DANIEL SALAS ◽  
EDUARD CESARI ◽  
KONSTANTIN SAPOZHNIKOV ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Internal Friction ◽  
Parent Phase ◽  
Reverse Transformation ◽  
High Concentration ◽  
Scanning Calorimetry ◽  
Internal Friction Peak ◽  
Transmission Electron ◽  
Interphase Boundaries

The effect of hyperstabilization of martensite implies that the reverse martensitic transformation proceeds in two well separated stages. Namely, a small fraction of martensite (of the order of 10%) retransforms upon heating into the parent phase over a temperature range slightly higher than the nominal reverse transformation temperature, whereas the rest of the martensite retransforms through a re-nucleation of fine lamellae of the parent phase. The renucleation stage of the transformation is well defined and requires strong overheating of the order of 300 K with respect to the nominal transformation. In this letter, the results are discussed of a study of the hyperstabilization effect in different martensitic structures: faulted [Formula: see text] martensite in Cu–Al–Be system and twinned martensite in ferromagnetic Ni–Fe–Ga crystals by means of differential scanning calorimetry, transmission electron microscopy and internal friction. The conclusion has been drawn that hyperstabilization implies a severe blocking of the motion of interphase boundaries during the reverse transformation, which can be produced either due to a high concentration of highly mobile quenched-in defects ("sweeping" of defects during the reverse transformation) or due to a creation of obstacles by preliminary plastic deformation. The former mechanism requires very intense diffusion of quenched-in defects assisted by dislocations/interfaces, which has been confirmed by internal friction studies. It has been shown that the renucleation stage, which occurs at around 600 K for different alloys, is preceded by a relaxation internal friction peak. A possible role of this relaxation in renucleation of the parent phase is discussed.

EFFECT OF PRE-DEFORMATION ON DAMPING CAPACITY OF TINI/NBTI COMPOSITE

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2392-2397 ◽  
Author(s):  
JIANG JIANG ◽  
LISHAN CUI ◽  
YANJUN ZHENG ◽  
TINGYONG XING ◽  
XINGQING ZHAO ◽  
...  
Keyword(s):  
Internal Friction ◽  
Elastic Strain ◽  
Strain Energy ◽  
Parent Phase ◽  
Elastic Strain Energy ◽  
Damping Capacity ◽  
Internal Friction Peak ◽  
Pinning Effect ◽  
Damping Behavior ◽  
Martensitic Variants

The present work aims to investigate the internal friction and effect of pre-deformation on damping capacity of Nb 60 Ti 25 Ni 15 alloy, which could be considered as TiNi / NbTi metal matrix composite. The internal friction results showed that this composite possesses excellent damping behavior, which is associated with the movement of a set of abundant interfaces, such as those between the TiNi and NbTi phases, those between martensitic variants and those between martensite and parent phase. Meanwhile, the peak temperature and the width of the internal peak increased with increasing of prestrain level. It appears to be due to the release of the stored elastic strain energy, or the pinning effect by the deformed structures. Furthermore, the height of internal friction peak decreased as the prestrain level increased.

High-Temperature Mechanical Relaxation due to Dislocation Motion inside Dislocation Networks

2008 ◽  
Vol 137 ◽  
pp. 21-28 ◽  
Author(s):  
Andre Rivière ◽  
Michel Gerland ◽  
Veronique Pelosin
Keyword(s):  
Internal Friction ◽  
Relaxation Effect ◽  
Dislocation Motion ◽  
Relaxation Peak ◽  
Mechanical Relaxation ◽  
In Situ Tem ◽  
Mechanical Spectroscopy ◽  
Internal Friction Peak ◽  
First Case ◽  
Dislocation Walls

Internal friction peaks observed in single or polycrystals are clearly due to a dislocation relaxation mechanism. Because a sample observed by transmission electron microscopy (TEM) often exhibits in the same time various dislocation microstructures (isolated dislocations, dislocation walls, etc.) it is very difficult to connect the observed relaxation peak with a particular dislocation microstructure. Using isothermal mechanical spectroscopy (IMS), it is easier to compare, for instance, the evolution of a relaxation peak with measurement temperature to the microstructural evolution observed by in-situ TEM at the same temperatures. IMS was used to study a relaxation peak in a 5N aluminium single crystal firstly 1% cold worked and then annealed at various temperatures. TEM experiments performed in the same material at various temperatures equal to the temperatures used for the damping experiments made possible to link this internal friction peak with a relaxation effect occurring inside dislocation walls. In two other experiments in a 4N aluminium polycrystal and in a metal matrix composite with SiC whiskers, it is shown that the observed relaxation peaks are connected to the motion of dislocations inside polygonization boundaries in the first case and in dislocation pile-ups around each whisker in the second one. Theoretical models proposed to explain such relaxation peaks due to a dislocation motion inside a dislocation wall or network are discussed.

Internal Friction during Reverse Martensitic Transformation in Mn-Cu Alloy with 45 % Mn

2013 ◽  
Vol 738-739 ◽  
pp. 183-186 ◽  
Author(s):  
Galina Viktorovna Markova ◽  
Ekaterina Sergeevna Klyueva
Keyword(s):  
Heat Treatment ◽  
Martensitic Transformation ◽  
Low Temperature ◽  
Internal Friction ◽  
Temperature Dependence ◽  
Strain Amplitude ◽  
Physical Mechanism ◽  
Amplitude Dependence ◽  
Internal Friction Peak ◽  
Cu Alloy

The temperature and amplitude dependence of internal friction fcc Mn45Cu55 alloy aged at 400 °C were studied. Two low-temperature internal friction peak observed in the quenched state. Physical mechanism of the peaks was determined by the effect of frequency and strain amplitude on the temperature dependence of internal friction. The influence of the heat treatment to the internal friction of the investigated alloy was shown.

scholarly journals Lockdown e “Chiesa in uscita”. Un caso di studio in Italia: la fraternità “AGBP”

2021 ◽  
Vol 6 (13) ◽  
pp. 131-142
Author(s):  
Daniela Turco
Keyword(s):  
Catholic Church ◽  
Essential Role ◽  
Social Bonds ◽  
The Other ◽  
Focus Attention ◽  
Daily Lives ◽  
On Line ◽  
The Many ◽  
The One

The impetuosity of the Sars-Covid 2 infection has been remarkable, quickly upsetting the habits of individuals in every seat of the planet. We can observe, on the one hand, the individuals, lost and called to redefine every area of their daily lives. On the other, the institutions that, seizing this loss, have been called to play their essential role of creating and strengthening social bonds. The Catholic Church has promoted respect for the norms, without renouncing a “religious offer” which seems to have responded to an effective demand for accompaniment with a lot of possibility to chose on line liturgical celebrations, with a multiplicity of forms and possibilities of access. Among the various options possible, it was decided to focus attention on a specific case: the case of the fraternity “Amici di Gesù Buon Pastore” (AGBP), which has experienced a significant increase in its followers in the days of lockdown. In particular, we will ask ourselves what so many spiritual-followers have been looking for and if (and how) this interest, born during the quarantine period, can transform the new forms of religious belonging into a context where the historical religions seem to be unattractive if compared to the many alternatives of spirituality present on the “market”.

Frequency Dependence of the Internal Friction for Ti50Ni48.5Fe1.5 Shape Memory Alloy

2010 ◽  
Vol 143-144 ◽  
pp. 1007-1011
Author(s):  
Ting Yong Xing ◽  
Xu Jun Mi ◽  
Xiang Qian Yin ◽  
Bao Dong Gao ◽  
Yan Feng Li
Keyword(s):  
Phase Transformation ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Internal Friction ◽  
Shape Memory ◽  
Frequency Dependence ◽  
Internal Friction Peak ◽  
Interesting Phenomenon ◽  
Measuring Frequency ◽  
Friction Measurements

The objective of this work is to investigate the influence of measuring frequency on the internal friction of Ti50Ni48.5Fe1.5 shape memory alloy. The DSC, DC electrical resistivity and internal friction measurements were employed to characterize the sample in this study. Comparing the DSC result, the two internal friction peaks were confirmed which are corresponding to the R-phase transformation and martensitic transformation of Ti50Ni48.5Fe1.5 alloy during the cooling process, respectively. The height of internal friction peak corresponding to martensitic transformation increased with decreasing of measuring frequency. But, the height of the internal friction peak corresponding to R-phase transformation exhibited little measuring frequency dependence. Meanwhile, the value of the relative modulus peaks of the specimen increased with measuring frequency increasing. Furthermore, there was an interesting phenomenon that the martensitic transformation finish temperature shifted to higher temperature side with increasing of measuring frequency. It could be associated with the variation of applied vibration energy.

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