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Author |
Radi, A.; Khalil-Allafi, J.; Etminanfar, M.R.; Pourbabak, S.; Schryvers, D.; Amin-Ahmadi, B. |
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Title |
Influence of stress aging process on variants of nano-N4Ti3precipitates and martensitic transformation temperatures in NiTi shape memory alloy |
Type |
A1 Journal article |
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Year  |
2018 |
Publication |
Materials & design |
Abbreviated Journal |
Mater Design |
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Volume |
262 |
Issue |
262 |
Pages |
74-81 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
In this study, the effect of a stress aging process on the microstructure and martensitic phase transformation of NiTi shape memory alloy has been investigated. NiTi samples were aged at 450 degrees C for 1 h and 5 h under different levels of external tensile stress of 15, 60 and 150 MPa. Transmission electron microscopy (TEM) was used to characterize different variants and morphology of precipitates. The results show that application of all stress levels restricts the formation of precipitates variants in the microstructure after I h stress aging process. However, all variants can be detected by prolonging aging time to 5 h at 15 MPa stress level and the variants formation is again restricted by increasing the stress level. Moreover, the stress aging process resulted in changing the shape of precipitates in comparison with that of the stress-free aged samples. Coffee-bean shaped morphologies were detected for precipitates in all stress levels. According to the Differential Scanning Calorimetry (DSC) results, the martensite start temperature (M-s) on cooling shifts to higher temperatures with increasing the tensile stress during the aging process. This can be related to the change ofaustenite to martensite interface energy due to the different volume fractions and variants of precipitates. (c) 2018 Elsevier Ltd. All rights reserved. |
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Wos |
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Publication Date |
2018-01-04 |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0264-1275 |
ISBN |
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Additional Links |
UA library record; ; WoS full record; WoS citing articles |
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Impact Factor |
4.364 |
Times cited |
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Open Access |
OpenAccess |
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Notes |
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Approved |
Most recent IF: 4.364 |
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Call Number |
UA @ lucian @ c:irua:149854 |
Serial |
4938 |
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Author |
Khalil-Allafi, J.; Amin-Ahmadi, B. |
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Title |
Effect of mold hardness on microstructure and contraction porosity in ductile cast iron |
Type |
A1 Journal article |
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Year |
2011 |
Publication |
Journal of iron and steel research international |
Abbreviated Journal |
J Iron Steel Res Int |
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Volume |
18 |
Issue |
4 |
Pages |
44-47 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
The effect of mold hardness on the microstructure of ductile iron and the contraction porosity was investigated. Molds with different hardnesses (0.41, 0.48, 0.55, 0.62 MPa) and a sand mold prepared by Co2 method were used. The influence of silicon content on the induced expansion pressure owing to the formation of graphite was also investigated. The contraction during solidification can be compensated by an induced expansion owing to the graphite relief when the hardness of mold increases; therefore, the possibility of achieving a sound product without using any riser increases. |
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Wos |
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Publication Date |
2011-05-01 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1006-706X; |
ISBN |
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Additional Links |
UA library record |
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Impact Factor |
0.836 |
Times cited |
1 |
Open Access |
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Notes |
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Approved |
Most recent IF: 0.836; 2011 IF: 0.213 |
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Call Number |
UA @ lucian @ c:irua:122044 |
Serial |
823 |
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Author |
Khalil-Allafi, J.; Amin-Ahmadi, B. |
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Title |
Influence of mold preheating and silicon content on microstructure and casting properties of ductile iron in permanent mold |
Type |
A1 Journal article |
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Year |
2011 |
Publication |
Journal of iron and steel research international |
Abbreviated Journal |
J Iron Steel Res Int |
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Volume |
18 |
Issue |
3 |
Pages |
34-39 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
The effects of the mold preheating and the silicon content of ductile iron on the percentage of carbides, graphite nodule counts and shrinkage volume were investigated. The results showed that the percentage of carbides and the shrinkage volume decreased when the mold preheating increased. The ductile iron with the carbon equivalent of 4.45% and the silicon content of 2.5% without any porosity defects was achieved when the mold preheating was 450 °C. Increasing the silicon content in the range of 2.1%3.3% led to the increase in graphite nodule count and graphite size and the decrease in percentage of carbides. It is due to the increase in induced expansion pressure during the graphite formation with the increasing of silicon content. The suitable condition for casting a sound product of ductile iron without the riser at the mold preheating temperature of 300 °C is the silicon content of 3.3% and carbon equivalent of 4.7%. |
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Place of Publication |
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Wos |
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Publication Date |
2011-03-28 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1006-706X; |
ISBN |
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Additional Links |
UA library record |
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Impact Factor |
0.836 |
Times cited |
3 |
Open Access |
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Notes |
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Approved |
Most recent IF: 0.836; 2011 IF: 0.213 |
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Call Number |
UA @ lucian @ c:irua:122043 |
Serial |
1629 |
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Author |
Khalil-Allafi, J.; Amin-Ahmadi, B. |
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Title |
Multiple-step martensitic transformations in the Ni51Ti49 single crystal |
Type |
A1 Journal article |
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Year |
2010 |
Publication |
Journal of materials science |
Abbreviated Journal |
J Mater Sci |
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Volume |
45 |
Issue |
23 |
Pages |
6440-6445 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Multiple-step martensitic transformations of an aged Ni51Ti49 single crystal using calorimetric method were investigated. Results show that for short aging times (1045 min) multiple-step martensitic transformations on cooling occur in two steps. Applying intermediate aging times (1.254 h) results in three steps and long aging times (more than 8 h) lead to two-step martensitic transformations again. This behavior has not been recognized in NiTi single crystals in literatures. It can be related to the heterogeneity of composition and stress fields around Ni4Ti3 precipitates. |
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Place of Publication |
London |
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Wos |
000282429400021 |
Publication Date |
2010-06-30 |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0022-2461;1573-4803; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.599 |
Times cited |
5 |
Open Access |
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Notes |
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Approved |
Most recent IF: 2.599; 2010 IF: 1.859 |
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Call Number |
UA @ lucian @ c:irua:122046 |
Serial |
2231 |
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Author |
Khalil-Allafi, J.; Amin-Ahmadi, B.; Zare, M. |
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Title |
Biocompatibility and corrosion behavior of the shape memory NiTi alloy in the physiological environments simulated with body fluids for medical applications |
Type |
A1 Journal article |
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Year |
2010 |
Publication |
Materials science and engineering: part C: biomimetic materials |
Abbreviated Journal |
Mat Sci Eng C-Mater |
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Volume |
30 |
Issue |
8 |
Pages |
1112-1117 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Due to unique properties of NiTi shape memory alloys such as high corrosion resistance, biocompatibility, super elasticity and shape memory behavior, NiTi shape memory alloys are suitable materials for medical applications. Although TiO2 passive layer in these alloys can prevent releasing of nickel to the environment, high nickel content and stability of passive layer in these alloys are very debatable subjects. In this study a NiTi shape memory alloy with nominal composition of 50.7 atom% Ni was investigated by corrosion tests. Electrochemical tests were performed in two physiological environments of Ringer solution and NaCl 0.9% solution. Results indicate that the breakdown potential of the NiTi alloy in NaCl 0.9% solution is higher than that in Ringer solution. The results of Scanning Electron Microscope (SEM) reveal that low pitting corrosion occurred in Ringer solution compared with NaCl solution at potentiostatic tests. The pH value of the solutions increases after the electrochemical tests. The existence of hydride products in the X-ray diffraction analysis confirms the decrease of the concentration of hydrogen ion in solutions. Topographical evaluations show that corrosion products are nearly same in all samples. The biocompatibility tests were performed by reaction of mouse fibroblast cells (L929). The growth and development of cells for different times were measured by numbering the cells or statistics investigations. The figures of cells for different times showed natural growth of cells. The different of the cell numbers between the test specimen and control specimen was negligible; therefore it may be concluded that the NiTi shape memory alloy is not toxic in the physiological environments simulated with body fluids. |
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Corporate Author |
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Thesis |
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Publisher |
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Place of Publication |
Lausanne |
Editor |
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Language |
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Wos |
000282905600006 |
Publication Date |
2010-06-23 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0928-4931; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.164 |
Times cited |
34 |
Open Access |
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Notes |
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Approved |
Most recent IF: 4.164; 2010 IF: 2.180 |
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Call Number |
UA @ lucian @ c:irua:122039 |
Serial |
242 |
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Author |
Khalil-Allafi, J.; Amin-Ahmadi, B. |
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Title |
The effect of chemical composition on enthalpy and entropy changes of martensitic transformations in binary NiTi shape memory alloys |
Type |
P3 Proceeding |
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Year |
2009 |
Publication |
Journal Of Alloys And Compounds |
Abbreviated Journal |
J Alloy Compd |
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Volume |
487 |
Issue |
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Pages |
363-366 |
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Keywords |
P3 Proceeding; Condensed Matter Theory (CMT) |
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Abstract |
In the present research work the binary NiTi alloys with various compositions in the range of 50.351 at.% Ni were used. Samples have been annealed at 850 °C for 15 min and then quenched in water. In order to characterize transformation temperatures and enthalpy changes of the forward and the reverse martensitic transformation, Differential Scanning Calorimetric (DSC) experiments were performed. The enthalpy and entropy changes as a function of Ni atomic content have been thermodynamically investigated. Results show that enthalpy and entropy changes of martensitic transformation decrease when Ni atomic content increases. The variation of enthalpy and entropy of martensitic transformation with Ni content in binary NiTi alloys were explained by thermodynamic parameters and electron concentration of alloy (e/a) respectively. |
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Publisher |
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Place of Publication |
Amsterdam |
Editor |
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Language |
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Wos |
000272521900073 |
Publication Date |
2009-07-31 |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
Proceedings of the 22nd International Conference on the Physics of Semiconductors |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0925-8388; |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
3.133 |
Times cited |
30 |
Open Access |
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Notes |
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Approved |
Most recent IF: 3.133; 2009 IF: 2.135 |
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Call Number |
UA @ lucian @ c:irua:122040 |
Serial |
804 |
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