Effect of stacking fault probability on {gamma}-{var_epsilon} martensitic transformation and shape memory effect in Fe-Mn-Si based alloys
- Shanghai Jiao Tong Univ. (China). Dept. of Materials Science
As an important parameter in Fe-Mn-Si based shape memory alloys, the stacking fault probability of {gamma}-phase, P{sub sf}, has been determined by means of X-ray diffraction profile analysis and connected with some macro-behavior such as the starting temperature of the thermo-induced {gamma} {yields} {var_epsilon} transformation, M{sub s}, the critical stress required for inducing {var_epsilon}-martensite, {sigma}{sub M}, the strain-hardening exponent, n, etc. It is revealed that a linear relationship between M{sub s} and the reciprocal of P{sub sf} is established as M{sub s} = 372 {minus} 0.113/P{sub sf}, and also between {sigma}{sub M} and the reciprocal of P{sub sf}, as {sigma}{sub M} = 29 + 0.212/P{sub sf}. It is shown that the strain-hardening exponent n changes monotonically with P{sub sf}. Adding Cr or N, and increasing the content of Mn in a Fe-30Mn-6Si alloy will decrease P{sub sf}, resulting in the reducing of M{sub s} and n, and the increasing of {sigma}{sub M}. The existence of quenched-in vacancies will promote the enhancement of P{sub sf}, that leads to the increase in M{sub s}. The variation of {gamma}-grain size has no obvious effect on P{sub sf}, so that it does not affect the M{sub s} temperature. The thermo-mechanical cycling will increase P{sub sf}, in turn will lower {sigma}{sub M} and increase n, so that the shape memory effect is improved. The possible mechanism is discussed.
- OSTI ID:
- 616195
- Journal Information:
- Acta Materialia, Vol. 46, Issue 2; Other Information: PBD: 5 Jan 1998
- Country of Publication:
- United States
- Language:
- English
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