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  • 1
    Electronic Resource
    Electronic Resource
    Influence of Thermal Cycling and Equivalent Heat Treatment on Amplitude Dependence of Internal Friction in Cu-Al-Mn Shape Memory Alloys (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 137 (Mar. 2008), p. 137-144 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The influence of thermal cycling between - 196 °C and 200 °C and equivalent heattreatment at 200 °C on the amplitude dependence of internal friction at room temperature has beenstudied in as cast Cu – Al - Mn shape memory alloys with different chemical compositions. UsingX-ray diffraction one composition was found to be austenitic and two others martensitic with twomartensite types (2H and 18R) at room temperature. All specimens were thermally cycled for 100times. During one thermal cycle the specimen underwent altogether two phase transformations onein each direction. Thermal cycling causes microstructural changes in the specimens due to atomicreordering, thermal stresses, which are generated in the martensitic state due to the anisotropy ofthermal expansion, or due to the nucleation and propagation of interphase cracks in parent phase.During repeated thermal cycling the transition peaks obtained in mechanical spectroscopy becamenarrower due to an enduring change of the microstructure and annealing effect at 200 °C. Tocompare between the effects of thermal cycling and heat treatment one martensitic specimen wasannealed at 200 °C. For selected cycle numbers and heat treatment times the amplitude dependenceof damping was measured at room temperature. The influence of thermal cycling of martensiticspecimens on the damping level was found to be similar to the influence of heat treatment at200 °C. It is most likely that the highest heat treatment temperature is more important for theamplitude dependence of damping than the temperature change during thermal cycling. Cracks dueto thermal cycling were found in all cycled specimens. They have no significant effect on theamplitude dependence of damping of the martensitic samples, whereas some small influence couldbe observed in austenitic samples at room temperature
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.137.137.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanical and Fatigue Properties of Cu-Al-Mn Shape Memory Alloys with Influence of Mechanical Cycling on Amplitude Dependence of Internal Friction at Room Temperature (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 137 (Mar. 2008), p. 145-154 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The mechanical and fatigue properties of Cu - Al - Mn shape memory alloys withdifferent phase fractions at room temperature were investigated. The specimens with differentchemical compositions (Al: 8.9 - 12.5 wt. % and Mn: 3.3 - 9.3 wt. %) were tensile loaded with 10-3s-1 tensile strain rate. Austenitic specimens have the highest tensile strength and fracture strain.Yield strength, tensile strength and elongation of martensitic alloys were lower compared withaustenitic alloys. Fracture strain of martensitic alloys depend only little on the chemicalcomposition. Specimens of martensitic, austenitic and three different multiple phase specimenswere tested in the high cycle fatigue range at room temperature. The Woehler curves for multiplespecimens depend on the phase fraction at testing temperatures. Different elements as Co, Ni, Feand Si were alloyed to CuAl11.6Mn5. All decreased the ductility of the specimens, and their fatigueproperties.Maxima could be detected in the strain amplitude dependence of damping for multiple phasespecimen. These maximum are shifted to lower damping and to higher strains with increasingnumber of mechanical cycles, compared to the as cast condition for not cycled specimen. The strainamplitude dependence of damping in martensitic and austenitic Cu – Al – Mn shape memory alloysdoes not change much during mechanical cycling
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.137.145.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of Heat Treatment on Magnetic and Damping Properties of Fe-11 at.% Al Alloys (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 137 (Mar. 2008), p. 129-136 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The influence of heat treatment on the amplitude dependence of internal friction in Fe -11 at. % Al alloys with carbon contents in the range 0.005 - 0.2 at. % has been studied using aninverted torsion pendulum in the temperature range 300 – 950 K and a vibrating reed apparatus atroom temperature. The specimens were annealed at 1273 K in vacuum and cooled down withdifferent cooling rates in order to obtain different degrees of order. It was found that ordering ishardly avoidable in Fe - Al alloys with Al contents 〉 11 at. %. Ordered alloys are characterised bylower damping capacity due to higher coercivity caused by additional pinning of magnetic domainwalls by antiphase boundaries. X-ray diffraction investigations indicate that water-coolingsuppresses ordering in Fe - 11 at. % Al alloys while cooling in air or in furnace provokes D03–typeordering. Slowly cooled specimens are characterised by higher damping capacity due to lowercoercivity than water cooled or plastically deformed specimens. The amplitude dependentmagneto-mechanical damping was determined as the difference between amplitude dependentdamping without and with saturating magnetic field (~ 20 kA/m). Magneto-mechanical dampingwas found to be proportional to the strain where the amplitude dependent damping is maximumand reciprocal to the coercivity and saturation polarisation. Cold rolling increases the coercivityand therefore decreases the magneto-mechanical damping. An increase of the grain size in theinvestigated samples by heat treatment leads to a qualitatively expected decrease of coercivity andtherefore to an increase of magneto-mechanical damping
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.137.129.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of Cold Rolling on the Damping of As Cast Cu-Al-Mn Shape Memory Alloys (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 137 (Mar. 2008), p. 155-162 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The ductility of Cu – Al – Mn shape memory alloys at room temperature depends on thealuminium content. High aluminium contents make Cu – Al – Mn very brittle and unsuitable forplastic shaping. Two Cu – Al – Mn shape memory alloys were investigated. The ductile alloyCuAl7.8Mn9.5 (all contents in wt. %) could be easily cold rolled by 86 %. The alloy CuAl12Mn4.3could be cold rolled by only 12 - 14 %. The amplitude dependence of damping of austeniticspecimens increased with increasing degree of cold work, whereas the damping of martensiticausteniticspecimens decreased. These observations can be explained by the creation of stressinduced martensite and therefore by new moveable interfaces like phase- and twin boundaries,which contribute to damping. Plastic deformation increases the dislocation density, too. Both theincrease of dislocation density and the increase of martensite content can lead to a decrease ofdamping mainly for high deformation degrees. Same shape memory alloys have shown negligiblehardness increase during cold rolling, too. This behaviour, untypical for metals, can be explained bythe generation of new martensite and by the fact that the hardness of martensite is smaller than thehardness of austenite. Some aging effects of the specimen after cold rolling, which lead to decreaseof damping, were detected. This can be explained by pinning of moveable interfaces by pointdefects and/or retransformation of martensite into austenite
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.137.155.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Anelastic Properties of Mg+3vol.%Gr Prepared by Ball Milling (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 319 (Sept. 2006), p. 189-196 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Internal friction in ultra-fine grained Mg with 3vol% of Graphite was measured by forcedvibration method at low frequencies of 0.1, 0.5, 1.0, and 2.0 Hz over a temperature range from roomtemperature to 753 K with continuous heating. The specimens were prepared by milling procedurein an inert atmosphere and subsequent compacted and hot extruded. Two developed peaks in theinternal friction spectrum were obtained at temperatures ≈ 350 K and ≈ 550 K. While the position ofthe first peak is frequency dependent, the second peak position is stable, independent of measuringfrequency. The activation energy of the low temperature peak was estimated. In the light of internalfriction measurements, the high temperature internal friction peak is attributed to the generation andmotion of dislocations produced by the difference in the coefficient of thermal expansion betweenthe Mg matrix and Gr phase at the matrix–particle interfaces
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/51/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.319.189.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Amplitude Dependent Internal Friction of CuAlMn Shape Memory Alloys (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 319 (Sept. 2006), p. 45-52 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The strain amplitude dependent internal friction at room temperature and the transitiontemperatures of CuAlMn-shape memory alloys with Al contents from 8.9 wt.% to 12.7 wt.% and Mncontents from 4.7 wt.% to 9.3 wt.% were investigated. The investigated strain range was 10-6 - 10-3.Rods of various compositions were die cast and machined to single clamped damping bars. Theirtransition temperatures and amplitude dependent damping was determined in as cast and homogenizedstate. The damping in the investigated shape memory alloys was found to be generally much higherthan in metals without martensitic transition. In as cast state some alloys exceeded the damping of aSonoston type alloy measured in comparison for strains higher than 3 x 10-5. The influence of grain sizeon damping was investigated by additional sand casting and the use of Boron for grain refinement. Itwas found that only the material with the biggest grains had a noticeable higher damping over thewhole measured strain range. Homogenization heat treatment can still extremely increase the dampingof CuAlMn alloys. After homogenization this extremely high damping decreases slowly to mediumvalues in the order of as cast alloys
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/51/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.319.45.pdf
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