Structural Changes Caused by High-Temperature Holding of Powder Shape Memory Alloy 66% Fe – 14% Mn – 6% Si – 9% Cr – 5% Ni

Pricop, Bogdan; Özkal, Burak; Söyler, U.; Humbeeck, Jan Van; Lohan, Nicoleta Monica; Suru, Marius-Gabriel; Spiridon, Iuliana; Bujoreanu, Leandru-Gheorghe

doi:10.1007/s11041-016-9921-y

Cited by 7 publications

(8 citation statements)

References 23 publications

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“…Typical structures comprise long plates of two variants (LP1 and LP2) and a shorter plate (SP3) separated by the long ones. These results sustain the conclusion that MA promotes the formation of α -(bcc) martensite, after heat treatment at 1,200 • C in low vacuum, argon or nitrogen, both at short and long holding periods, while ε-hcp martensite formed only after 80 min holding in argon or nitrogen (Pricop et al, 2016).…”

Section: Thermomechanical Processing and Pre-straining Effectssupporting

confidence: 86%

“…In the particular case of 50_MA specimens, the effects of holding environment (protective atmosphere) and time, during the heat treatment at 1,200 • C followed by water quenching, were investigated, as summarized in Figure 7 (Pricop et al, 2016).…”

Section: Thermomechanical Processing and Pre-straining Effectsmentioning

confidence: 99%

“…Effects of holding environment (protective atmosphere: low vacuum, argon and nitrogen) and time (10, 80 min) on the structure of 50_MA specimens heat treated at 1,200 • C (reproduced afterPricop et al, 2016, with permission granted by Springer Nature).…”

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Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

et al. 2020

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In the case of quintenary Fe-Mn-Si-Cr-Ni shape memory alloys (SMAs), ingot metallurgy (IM) has technological shortcomings concerning compositional segregation, imperfect melt-incorporation of Si, demanganization during heating and cooling-induced cracking, which can be effectively surmounted by combining powder metallurgy (PM) with mechanical alloying (MA). The paper reviews the results reported in the processing and characterization of PM-MA'ed FeMnSiCrNi SMAs, with special emphasis on the findings obtained by present authors in the last decade. Specimens with nominal chemical compositions Fe-18Mn-3Si-7Cr-4Ni and Fe-14Mn-6Si-9Cr-5Ni (mass %) were produced by IM and PM. In the latter case various volume fractions of as-blended powders were MA'ed under protective atmosphere, before being pressed and sintered. Further compacting, up to 5% porosity degrees, was achieved by hot rolling. Structural analysis, performed by X-ray diffraction and scanning electron microscopy, revealed the formation of unusually large amounts of α-body centred cubic (bcc) thermally induced martensite. This undesirable martensite seemed to be destabilized by tensile pre-straining, and enabled PM specimens to reach higher stresses than IM ones. The formation and accumulation of α-bcc stress induced martensite was enhanced by tensile pre-straining, mechanical cycling and augmentation of MA'ed powder fraction. It has been argued that the optimization of technological processing parameters of heat treatment (HT) and hot rolling (HR) combined with MA'ed powder fraction caused the augmentation of shape memory effect (SME) magnitude. DMA-temperature scans revealed an increasing tendency of internal friction (tan δ) with MA'ed powder fraction, as well as the presence of two tan δ maxima ascribed to antiferromagneticparamagnetic transition and martensite reversion to austenite, respectively. DMA-strain sweeps emphasized the occurrence of a plateau on the storage modulus vs. strain amplitude variation which was associated with stress-induced formation of ε hexagonal close-packed (hcp)-martensite. In spite of large α-bcc amounts, PM-MA'ed Fe-14Mn-6Si-9Cr-5Ni experienced free-recovery SME which was enhanced by thermomechanical training. Coupling rings, meant to connect vibrating pipes that transport turbulent fluids, being able to mitigate vibrations that could accidentally open the connection, were manufactured and tested.

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Section: Thermomechanical Processing and Pre-straining Effectssupporting

confidence: 86%

Section: Thermomechanical Processing and Pre-straining Effectsmentioning

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Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

et al. 2020

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“…% fraction of mechanically alloyed (MA) powders obtained after high energy ball milling under argon atmosphere [12] for the duration of 4u3.6 ks, which enabled optimal densification of compacted samples [16]. After pressing (500 MPa) and sintering (under argon atmosphere at 1423 K for 2 u 3.6 ks), in order to further increase specimens compactness, six consecutive hot rolling passes were performed at 1373 K, without allowing the billets to cool down to room temperature (RT), until reaching a thickness of 1 mm [17]. Hot rolling was performed with an experimental setup, comprising a tubular electric furnace and flat cylinders roller, which seized the billets when being pushed out the furnace, by a long flat-head rod [18].…”

Section: Powder Sinteringmentioning

confidence: 99%

Powder metallurgy and mechanical alloying effects on the formation of thermally induced martensite in an FeMnSiCrNi SMA

Pricop

Mihalache

Lohan

et al. 2015

MATEC Web of Conferences

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Abstract. By ingot metallurgy (IM, melting, alloying and casting), powder metallurgy (PM, using as-blended elemental powders) and mechanical alloying (MA of 50 % of particle volume), three types of FeMnSiCrNi shape memory alloy (SMA) specimens were fabricated, respectively. After specimen thickness reduction by hot rolling, solution treatments were applied, at 973 and 1273 K, to thermally induce martensite. The resulting specimens were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), in order to reveal the presence of ε (hexagonal close-packed, hcp) and α' (body centred cubic, bcc) thermally induced martensites. The reversion of thermally induced martensites, to γ (face centred cubic, fcc) austenite, during heating, was confirmed by dynamic mechanical analysis (DMA), which emphasized marked increases of storage modulus and obvious internal friction maxima on DMA thermograms. The results proved that the increase of porosity degree, after PM processing, increased internal friction, while MA enhanced crystallinity degree.

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“…The substitution of a fraction of as blended powders with MA'd particles contributed to the reduction of surface oxidation [23] being associated with the presence of amorphous regions in PM-MA powder mixtures [24] of Fe-14Mn-6Si-9Cr-5Ni SMAs. In solution treated state, mechanical alloying enabled the increase of α'-bcc martensite amount [25] but with a suitable combination of MA'd powder fraction and corresponding selection of the parameters for sintering, rolling and solution treatment [26] an increase of shape recovery degree was recently observed in Fe-14Mn-6Si-9Cr-5Ni SMAs [27]. Based on the promising results, reported by some of present authors, on the influence of heat treatment temperature and pre-straining magnitude on the formation of stress induced martensite in ingot metallurgy Fe-MnSi-Cr-Ni SMA [28], the present paper aims to study the same aspects in a PM SMA by considering the effects of substituting various fractions of as-blended powders with MA'd ones.…”

Section: Introductionmentioning

confidence: 99%

Factors influencing martensite transitions in Fe-based shape memory alloys

Mihalache

Pricop

Suru

et al. 2015

MATEC Web of Conferences

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Abstract. Fe-14Mn-6Si-9Cr-5Ni (mass %) shape memory alloy (SMA) specimens were obtained by powder metallurgy in as-blended state (0_MA) and with particle volume fractions of 10 and 20 % MA'd powders, respectively. After hot rolling and solution treatment, between 973 and 1373 K, the specimens were pre-strained up to 4 %, on a tensile testing machine. The influences of: (i) MA'd fractions, (ii) solution treatment temperature and (iii) pre-straining degree were analysed by X-ray diffraction (XRD), optical (OM) and scanning electron (SEM) microscopy. In this purpose, the gauges of pre-strained specimens were cut and metallographically prepared. Dynamic mechanical analysis (DMA) was employed to emphasize the reverse transformation, during heating, of thermally induced martensite, obtained after solution treatment. The results proved that, as an effect of PM-MA processing, mechanical properties were improved, the amount of stress induced martensite increased and the reverse martensitic transformation was enhanced.

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Structural Changes Caused by High-Temperature Holding of Powder Shape Memory Alloy 66% Fe – 14% Mn – 6% Si – 9% Cr – 5% Ni

Cited by 7 publications

References 23 publications

Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

Powder metallurgy and mechanical alloying effects on the formation of thermally induced martensite in an FeMnSiCrNi SMA

Factors influencing martensite transitions in Fe-based shape memory alloys

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