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Microstructural and thermal analysis of Cu-AI-Mn- Ag shape memory alloys

Two quaternary Cu-Al-Mn-Ag shape memory alloys with nearly constant Al and Ag contents and variable content of Mn were prepared by arc melting of pure metals. Experimentally determined overal! compositions of the investigated alloys were Cu-9.4%Al-1 .1%Mn- 3.7%Ag (alloy 1) and Cu-9.5%Al-5.6%Mn-3.9%Ag (alloy 2) (in wt.%). Microstructures of the prepared samples were investigated in the asprepared condition and after heat treatment which included solution annealing at 850 "C followed by quenching into the water at room temperature. The effects of alloy composition and heat treatments on the microstructure and transformation temperatures of the investigated shape memory alloys were investigated by using scanning electron microscopy coupled with energy dispersive spectroscopy (SEMEDS) and differential scanning calorimetry (DSC). It was determined that alloy with low Mn content (alloy 1) exhibits o+F two-phase microstructure in the as-prepared state and martensite+d two-phase microstructure in the as-quenched state. Ag was uniformly distributed between the coexisting phases. The microstructure of the alloy with a higher content of Mn (alloy 2) was fully martensitic in both investigated conditions. Phase transition temperatures, including martensite/auslenite transition, order/disorder transformation of austenite phase, dissolution of o precipitates and melting of the alloy were determined by using the DSC method.

Shape memory alloy, Cu-Al-Mn-Ag alloy, Microstructure, Martensitic transformation

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