Bainite precipitation in a Cu-Al-Mn-Gd shape memory alloy

Abstract In this study, the aging effects and bainite formation kinetics in the Cu71.2Al18.6Mn10.2 and Cu69.7Al18.9Mn10.3Gd1.10 shape memory alloys are evaluated using different experimental techniques. The results show that the Cu71.2Al18.6Mn10.2 and Cu69.7Al18.9Mn10.3Gd1.10 alloys exhibit aging hardening during bainite precipitation, reaching hardness values at about 370 HV. It is verified that the ferromagnetic β3 phase is produced during the bainite precipitation on the aging. The kinetic process is evaluated, and for the Cu69.7Al18.9Mn10.3Gd1.10 alloy, the activation energy value is ∼42 kJ.mol−1 while the alloy without Gd presents an activation energy value at about 62 kJ.mol−1. Gadolinium modifies the reaction mechanism analyzed due to their interaction with β1 and α phases, and the phase decomposition with Gd. In the studied alloys the bainite formation shows to be strongly related to the diffusive processes.