Effects of the alloying Mn and Co on the martensitic transformation behaviors and damping properties of Cu-Al-Fe high-temperature shape memory alloys

This study investigated the microstructures, martensitic transformation behaviors, and internal friction characteristics of Cu-14Al-4Fe-xMn and Cu-14Al-4Fe-xCo shape memory alloys (SMAs). The addition of Mn to Cu-14Al-4Fe SMAs decreased the martensitic transformation temperature of the alloys to below room temperature. The damping capacity of the internal friction peak gradually increased with the Mn addition to the Cu-14Al-4Fe-xMn SMAs because the Mn addition enhanced the atomic lattice mismatch of the crystal structure, lowering the energy barriers of the formation and movement of twin boundaries. In contrast, the addition of Co increased the martensite transformation temperature to a value higher than that of the unalloyed Cu-14Al-4Fe SMAs. However, the damping capacity of the Cu-14Al-4Fe-xCo SMAs decreased significantly with increasing Co content because of grain refinement and precipitate formation.