Comparison of microstructure and shape memory properties between two Cu-Al-Mn alloys produced by additive manufacturing technology

Abstract

In this work, two Cu-Al-Mn alloys, including Cu-12.5Al-3Mn alloy and Cu-12.5Al-3Mn-1Fe alloy, considering the powder core wire with a structure resistant to element burning as additive manufacturing materials, were prepared by arc melt deposition process. The microstructures were studied utilizing OM, SEM, and XRD. The shape recovery rates under different pre-strains and the recovery behavior under intense thermal stimulation were analyzed by bending tests. Results showed that after adding Fe, the microstructure of the Cu-12.5Al-3Mn alloy transformed from hyper-eutectoid structure to eutectoid structure, inhibiting the precipitation of the brittle γ2 phase. Cu-12.5Al-3Mn-1Fe alloy possessed narrower martensitic laths, a more satisfactory martensitic substructure, and better martensitic orientation consistency than Cu-12.5Al-3Mn alloy due to the formation of a new κ phase after quenching. The shape recovery rate of the Cu-12.5Al-3Mn-1Fe alloy was maintained at 100% at a pre-strain of 4% to 8%, and then it started to decrease when the pre-strain reached 10%. The analysis result showed that Cu-12.5Al-3Mn-1Fe alloy, produced by additive manufacturing, has excellent shape memory properties, which not only result from the changes in the microstructure but are also attributed to the protective effect of the anti-damage structure of the powder core wire on the alloy elements.