Mechanism of the improvement of the shape memory effect by "training" and ausforming in Fe-Mn-Si based shape memory alloys

The effects of "training" and ausforming on the morphology of stress-induce d martensite and its reversion behavior to austenite in Fe-14Mn-6Si-9Cr-SNi and Fe28Mn-6Si-5Cr(mass%) alloys have been studied using atomic force micr oscopy (AFM), with the aim of clarifying the mechanism of the improvement o f the shape memory effect. It is found that uniformly distributed thin mart ensite plates with a single variant nature are formed in a grain for both o f the trained and ausformed samples. Those martensite plates can almost com pletely revert to the parent phase by shearing process, which is opposite t o that of the forward transformation. This complete reverse transformation produces a perfect shape memory effect.