Correlation between manganese variation, microstructure, shape memory behavior, ion release and nanotechnology-relevant features of Cu–Al–Mn alloys

Abstract

Cu–Al–Mn shape memory alloys (SMAs) are synthesized via powder metallurgy with Mn contents ranging from 1 to 9 wt.% while maintaining constant Al levels. The influence of Mn on microstructure, phase transformation, hardness, and chemical stability is systematically evaluated. Optical and SEM analyses showed a clear refinement of martensitic plates as Mn increased, progressing from coarse, well-defined variants in low-Mn alloys to fine, densely packed lamellae with partial β-phase retention in high-Mn compositions. XRD confirmed the presence of the martensitic Cu–Al–Mn phase with minor AlCu₃ peaks, alongside lattice contraction indicated by peak shifts. DSC revealed a substantial decrease in Ms, Mf, As, and Af with higher Mn, demonstrating β-phase stabilization. Hardness increased consistently due to solid-solution strengthening and martensitic refinement. Ion-release measurements showed enhanced chemical stability in high-Mn alloys, with CuAlMn5 exhibiting the lowest dissolution level. Overall, Mn effectively tailors structural and functional performance in Cu–Al–Mn SMAs. From a nanotechnology perspective, the progressive refinement of martensitic structures observed with increasing Mn content introduces nanoscale and sub-microscale features that are highly relevant for advanced functional materials. The formation of fine lamellar martensite, increased variant subdivision, and stabilized β-phase structures directly influence surface reactivity, ion release behavior, and mechanical response at small length scales. Such nanoscale microstructural control positions Cu–Al–Mn shape memory alloys as promising candidates for nanotechnology-driven applications, including micro-actuators, biomedical devices, and corrosion-resistant smart materials.