✍ Scribed by Bohong Jiang; Xuan Qi; Shaoxiong Yang; Weiming Zhou; T.Y. Hsu (Xu Zuyao)
No coin nor oath required. For personal study only.
AbstractÐAs an important parameter in Fe±Mn±Si based shape memory alloys, the stacking fault probability of g-phase, P sf , has been determined by means of X-ray diraction pro®le analysis and connected with some macro-behavior such as the starting temperature of the thermo-induced g 4 e transformation, M s , the critical stress required for inducing e-martensite, s M , the strain-hardening exponent, n, etc. It is revealed that a linear relationship between M s and the reciprocal of P sf is established as M s =372 À 0.113/ P sf , and also between s M and the reciprocal of P sf , as s M =29 + 0.212/P sf . It is shown that the strain-hardening exponent n changes monotonically with P sf . Adding Cr or N, and increasing the content of Mn in a Fe±30Mn±6Si alloy will decrease P sf , resulting in the reducing of M s and n, and the increasing of s M . The existence of quenched-in vacancies will promote the enhancement of P sf , that leads to the increase in M s . The variation of g-grain size has no obvious eect on P sf , so that it does not aect the M s temperature. The thermo-mechanical cycling will increase P sf , in turn will lower s M and increase n, so that the shape memory eect is improved. The possible mechanism is discussed.
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Fe-Mn-Si is a well-characterized ternary shape memory alloy. Research on this alloy has consistently shown that the addition of 5-6 wt.% Si is desirable to enhance the reversibility of stress-induced martensite vis-a `-vis shape memory. This paper examines the effect of Si on the morphology and the