Effects of Carbon Content and Thermo-Mechanical Treatment on Fe_{59}Mn_{30}Si_{6}Cr_{5}C_{X} (X = 0.015{\mathendash}0.1mass%) Shape Memory Alloys

Slight amounts of carbon (0:015{0:1mass%) were added into the Fe-30Mn-6Si-5Cr shape memory alloy. The microstructure, precipitation behaviour and shape memory performance of these Fe59Mn30Si6Cr5CX alloys with various thermo-mechanical treatments were investigated. Experimental results show that two particles, the -phase and M23C6 carbide, are observed within the grain-boundary phases. M23C6 carbide only appears in an alloy with high carbon content, but the -phase can form in all alloys with low and high carbon contents. The deformationinduced defects in the 10% pre-deformed specimens are preferential sites for nucleation of precipitates (the -phase and M23C6 carbide) in the following aging treatment. After 550{800 C aging, the rearranged uniform defects and homogeneous precipitates within the grain interior will strengthen the matrix and increase the shape recovery ability. After 850{900 C aging, both the uniform defects and homogeneous precipitates disappear due to recrystallization, and hence the specimen’s shape recovery ratios are significantly reduced. [doi:10.2320/matertrans.MRA2008122]