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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