The shape memory
effect and the microstructure in Fe Mn Si Cr Ni C shape memory alloys after aging have
been studied by SEM analysis. The shape recovery ratio in the alloy 1 with ultralow carbon contnet increases with increasing the aging time when aged at 1123K. The shape recovery ratio in alloy 2 with 0.18% carbon content increases with increasing aging time when the aging time is less than 300min, and a maximum value can be obtained at 300min. When greater than 300min, it will decrease gradually. The SEM analysis shows that the
second phase
particles precipitated both in grain boundary and inside grain of alloy 2, and these particles were carbides rich in chromium, manganese and silicon. While the second phase particles in alloy 1 precipitated only in grain boundary,whose composition is also different from that of alloy 2. The amount of the second phase particles in alloy 2 is much more than that in alloy 1. What is more, the growth velocity of the second phase particles in alloy 2 is also much faster than that in alloy 1. The shape memory effect in the tested alloy can be improved appreciably through strengthening austenite matrix by aging.