Chemical Resistance of Cu-Al-Mn Superelastic Alloy Bars in Acidic and Alkaline Environments

Abstract

Recently, single-crystal Cu-Al-Mn (CAM) superelastic alloy (SEA) bars have been developed to address the shortcomings of traditional Ni-Ti SEA bars, i.e., high cost, low workability, and lack of superelasticity at low temperatures. The CAM SEAs have a wide range of potential applications in biomedical, aerospace, mechanical, and civil industries. However, no quantitative information is available on the chemical stability of this relatively new metal alloy. This study quantified the chemical resistance of CAM SEA bars compared with that of mild steel bars in terms of mass loss and changes in mechanical and physical properties. Tensile testing was performed to estimate the reduction in the yield load of the samples after chemical aging. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were carried out to determine the oxidation potential of the material. Corrosion parameters of CAM SEAs were quantified through potentiodynamic polarization tests. The erosion rate of CAM SEAs was also estimated using these corrosion parameters to compare against the typical values reported for mild steel. The CAM SEAs had a chemical resistivity significantly superior to that of mild steel regardless of the environmental exposure conditions tested in this paper. It was also found that CAM SEAs have comparable corrosion resistance to another Cu-based shape memory alloy composition: Cu-Al-Ni.