Phase-State Control in As-Cast Cu–Al–Mn Shape Memory Alloys

Lovro Cigić, Aleš Nagode, Ivana Ivanić, Borut Kosec and Blaž Karpe

DOI: https://doi.org/10.64486/m.66.2.3
Online publication date: August 3, 2026

Abstract: Cu–Al–Mn shape memory alloys (SMAs) are attractive functional materials owing to their thermoelastic martensitic transformation, which enables the shape memory effect, superelasticity, and elastocaloric response. However, their practical application requires precise control of the transformation temperatures. In this study, the effect of Sn addition on the chemical homogeneity, microstructure, hardness, and transformation temperatures of as-cast Cu–Al–Mn–Sn alloys was investigated. CuAl9Mn9.5-based alloys with different Sn contents were fabricated by suction-assisted gravity casting, and their compositions were analyzed by energy-dispersive X-ray spectroscopy. Differential scanning calorimetry revealed that Sn addition systematically decreased the Ms, Mf, As, and Af  temperatures. A pronounced shift was already observed after adding 0.78 wt. % Sn, which reduced Af from 102.4 to 23.4 °C. Further Sn additions shifted the transformation interval into the sub-zero temperature range, with Af reaching −61.1 °C at 2.62 wt. % Sn. The transformation-temperature changes were accompanied by a transition from martensitic to austenitic room-temperature microstructure and increased hardness. These results demonstrate that Sn addition is an effective approach for tailoring the transformation temperature range of Cu–Al–Mn SMAs while maintaining casting consistency and chemical uniformity.

Keywords: Cu–Al–Mn shape memory alloy; Sn alloying; transformation temperatures; differential scanning calorimetry

This article is published online first and will appear in Metalurgija, Vol. 66, Issue 2 (2027).