Effect of Microstructure Control on Superelastic Property of Cu-Al-Mn Alloy

Cu-Al-Mn Shape Memory Alloys (SMAs) have high cold-workability with high cost performance. Their superelasticity (SE) are superior to conventional Cu-based SMAs. In this study, we obtained following results; The SE properties of Cu-Al-Mn SMAs are achieved by microstructural control such as grain size and texture. When the grain size is coarser than wire diameter, the SE stress is nearly constant and the SE strain of 10% is obtained. This is achieved by adding Co to the alloy. When the grain size is finer than wire diameter, the fatigue strength is improved. This is achieved by adding B to the alloy. The addition of Ni to the Cu-Al-Mn ternary alloy shows a drastic effect on the formation of the strong recrystallization texture. Even for a sheet specimens having small grain size, the SE strains of 6% can be obtained in an angle of 45 degree to the rolling direction. Coil springs made by this new SMA show superior properties to conventional SMAs.