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On role of atomic migration in amnesia occurrence during complex thermal cycling of Cu-Zn-Al shape memory alloy

Domenii publicaţii > Stiinte ingineresti + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: L.-G. Bujoreanu; N. M. Lohan; B. Pricop; N. Cimpoeşu

Editorial: Maney Publishing, Materials Science and Technology, 28(6), p.658-667, 2012.


The reproducibility of thermally induced reversible martensitic transformation, occurring in a Cu-15Zn-6Al (mass-%) shape memory alloy during heating, was studied on three different fragments of martensitic alloy subjected to complex thermal cycling comprising four series of five heating-cooling cycles, applied on a differential scanning calorimetry (DSC) device, between room temperature (RT) and three maximum temperatures: 453, 463 and 473 K respectively. After each series of heating-cooling cycles the fragments were naturally aged at RT for 37 days (∼3.2 Ms). Thermograms of DSC revealed a gradual diminution in the magnitude of martensite reversion to parent phase, accompanied by decreasing tendencies of both critical temperatures and transformation rates, which reflect a gradual loss of thermal memory, associated with ‘amnesia’ occurrence. Scanning electron microscopy observations coupled with energy dispersive X-ray spectroscopy performed at the end of complex thermal cycling revealed that ‘amnesia’ occurrence was associated with changes in the morphology of martensite plates, from parallel plate-like to interblocking needle-like, and with an increase of chemical fluctuations, as an effect of the intensification of atomic migration.

Cuvinte cheie: Thermal cycling; Shape memory alloy; Natural aging; Electron microscopy; Martensite; Differential scanning calorimetry