Iron-based superelastic alloys with near-constant critical stress temperature dependence

Abstract

Shape memory alloys recover their original shape after deformation, making them useful for a variety of specialized applications. Superelastic behavior begins at the critical stress, which tends to increase with increasing temperature for metal shape memory alloys. Temperature dependence is a common feature that often restricts the use of metal shape memory alloys in applications. We discovered an iron-based superelastic alloy system in which the critical stress can be optimized. Our Fe-Mn-Al-Cr-Ni alloys have a controllable temperature dependence that goes from positive to negative, depending on the chromium content. This phenomenon includes a temperature-invariant stress dependence. This behavior is highly desirable for a range of outer space–based and other applications that involve large temperature fluctuations.

On the Influence of Microstructure on the Corrosion Behavior of Fe–Mn–Al–Ni Shape Memory Alloy in 5.0 wt% NaCl Solution

“…To improve the resistance against corrosive attack, follow-up studies will focus on the influence of the chemical composition of the alloy as well as the influence of surface treatments and coatings, respectively, on the corrosion behavior of Fe-Mn-Al-Ni. The effect of Ti and Cr on the mechanical properties of the Fe-Mn-Al-Ni alloy has been investigated by Vollmer et al [31] Very recently, a pseudoleasltic response for single-crystalline samples with Cr content up to 7.5% was observed over a wide temperature range of À260 C to 200 C. [48] In general, the corrosion resistance of steels can be significantly improved by the addition of Cr. High-Mn steels with small amounts of Cr (3-6%) already show an improved corrosion behavior.…”

Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

“…In order to overcome these limitations, low-cost iron-based SMAs with superior machinability gained increased attention in recent years [4][5][6][7][8]. One of the most promising alloy systems is Fe-Mn-Al-Ni-X (X = Ti, Cr) [9][10][11][12]. For this alloy system superelastic strains up to 5% in polycrystals [11] and up to 10% in single crystals [11,13] have been reported.…”

Local chemical fluctuation mediated ultra-sluggish martensitic transformation in high-entropy intermetallics

“…5 In contrast, a large recoverable pseudo-elastic strain (>2%) can be achieved in alloys exhibiting a stress-induced diffusionless structural transformation ( i.e. , the so-called martensitic transformation), such as NiTi-, 3 Fe-, 6–8 and Cu 9 -based alloys, which is also referred to as superelasticity. The cubic unit cells of the parent phase spontaneously undergo the same distortion over a very long range (called long-range ordering of the strains) upon loading and hence form a distorted lattice called martensite.…”