Abstract
In copper-based shape memory alloys (SMAs), some exceptional phenomena, such as the shape memory effect (SME) or superelasticity (SE), are observable. However, commercial aluminum bronzes, Cu3Al-based alloys, do not present these functional properties (SME and/or SE) in their original state. Thus, since one of the main copper-based SMA systems is the Cu-Al-Ni alloy, this paper aims to analyze the modification of these commercial aluminum bronzes to SMA by the addition small amounts of Cu, Al and/or Ni. These modified bronzes were reprocessed by induction melting and injected by centrifugation into a ceramic coating mold. The modifications were made to determine the nominal composition for a Cu-13,0Al-4,0Ni (%wt) SMA. The effectiveness of the modifications was verified by differential scanning calorimetry (DSC) thermal analysis. All modified Cu-Al-Ni bronzes presented DSC peaks of the thermoelastic martensitic phase transformation, showing that SMA behavior was achieved, while the non-modified bronzes revealed no transformation. These results were supported by Vickers hardness (HV), X-ray diffraction (XRD), semi quantitative composition by EDS analysis and optical microscopy.
Highlights
Shape memory alloys (SMAs) are special metallic materials that present the functional phenomena of the shape memory effect (SME) and superelasticity (SE); they are classified as active or smart metals
The occurrence of the thermoelastic martensitic phase transformation in all modified bronzes reveal a strong potential for the shape memory effect to be achieved
The possibility of commercial aluminum bronzes to present the thermoelastic martensitic transformation and its origin in shape memory phenomena was investigated in this work
Summary
Shape memory alloys (SMAs) are special metallic materials that present the functional phenomena of the shape memory effect (SME) and superelasticity (SE); they are classified as active or smart metals. Both phenomena occur due to the thermoelastic martensitic phase transformation. The SMA undergoes a reversible martensitic transformation, allowing deformation through a twinning mechanism when temperatures are below the final martensite transformation limit (Mf)[1]. The nickel acts to retard the diffusion of aluminum in annealed Cu-Al alloys, eliminating the stable γ2 phase that does not undergo the martensitic transformation. It is known that the transformation temperatures of these
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