Cyclic Behavior and Microstructure Evolution under Temperature Change of Cu-Al Based Shape Memory Ribbons

cyclIc behavýour AND MICROSTRUCTURE EVOLUTION UNDER TEMPERATURE CHANGE OF Cu-Al BASED SHAPE MEMORY RIBBONS

SEMRA ERGEN, FIKRET YILMAZ,NECATI BASMAN,UGUR KOLEMEN,ORHAN UZUN

Gaziosmanpaþa University , Tokat, Turkiye, semraergengop@gmail.com

Cyclic behaviour of Cu-12Al-xBe (x: 0.4, 0.5, 0.6 wt %) shape memory ribbons fabricated by using melt-spinning tecnique was investigated. Cycling tests were conducted under the constant load of 50 mN and mechanical hysteresis was characterized through the calculation of energy dissipated in closed loops. Hadness and elastic modulus values were calculated in the each cycle. Phase and structure transformations in the Cu-12Al-xBe (x: 0.4; 0.5 and 0.6 wt.%) ribbons under  heating and cooling cycles from RT to high temperature ( approximately 200 °C) were studied  using a high–temperature X-ray diffractometer (HTXRD) and ESEM mode of SEM device. SEM analyses demonstrated that the microstructure of CuAlBe ribbons changed from martensite to austenite phase as temperature increasing. Reversible phase transformation was observed by cooling from high temperature to room temperature. The HTXRD analyses, in agreement with SEM revealed that the precipitation was formed in the microstructure of ribbon sample with 0.6Be content, which was the main reason of decrease in the shape recovery.

This work is supported by the Tokat Gaziosmanpasa University Scientific Research Project Unit (BAPB).