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Autori: S. Stanciu and L.G. Bujoreanu
Editorial: Elsevier, Materials Science and Engineering: A, 481-482, p.494-499, 2008.
The structure of a Cu-13.67Al-4.28Ni-0.54Mn-0.14Fe (wt.%) shape memory alloy was analyzed in the initial condition, during a heating-cooling cycle, and during a room temperature loading-unloading mechanical cycle. A fully reversible martensitic transformation was revealed which was associated with a shape recovery degree reaching a saturation value at 97.7% for a relative permanent deflection of 90 %. By X-ray diffraction, the occurrence of a reduced amount of β′1 stress-induced martensite (SIM) accompanied by the precipitation of the hard γ2-phase was noticed both during the heating of a martensitic specimen and during the air-cooling of the alloy in the austenitic state. It was assumed that a possible cause for the formation of β′1 SIM during heating or cooling could be the strains caused by the volume increase of hard γ2-phase that deformed the softer martensitic or the austenitic matrix. The irreversible formation of β′1 SIM at 100 MPa was revealed by X-ray diffraction in elongated condition and confirmed by OM at room temperature, after unloading.
Cuvinte cheie: β′1 Stress induced martensite; Shape recovery degree; γ2-Phase; Internal strains