Influence of addition of carbon nanotubes on structure–properties of Cu–Al–Ni shape memory alloys

Abstract

The influence of the addition of 0·2 wt-% carbon nanotubes on the microstructure and mechanical properties of Cu based shape memory alloy with a composition of Cu–11·5 wt-%Al–4·5 wt-%Ni were investigated using optical microscopy, X-ray diffraction, scanning electron microscopy and a universal testing machine. The experimental results show that the carbon nanotubes’ (CNTs’) addition has an effective influence on the martensite–austenite transformation temperatures, type, behaviour and morphology. Furthermore, the addition of CNTs can control the grain size and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect can be enhanced. Remarkably, the shape recovery ratio reached ∼68% of the original shape; this can be attributed to the precipitation and formation of the CNTs into the microstructure, effectively on the grain boundaries, which can help to reduce/relief the concentration of internal stress.