Analysis of compositional modification of commercial aluminum bronzes to obtain functional shape memory properties

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.