The Influence of α′ (bcc) Martensite on the Dynamic and Magnetic Response of Powder Metallurgy FeMnSiCrNi Shape Memory Alloys

Mocanu, Mihai; Mihalache, Elena; Pricop, Bogdan; Borza, F.; Grigoraş, M.; Comaneci, Radu; Özkal, Burak; Bujoreanu, Leandru-Gheorghe

doi:10.1007/978-3-319-76968-4_16

Cited by 4 publications

(14 citation statements)

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“…More recent studies corroborated the variations of storage modulus and magnetization, during heating. By associating storage modulus and magnetization increases, observed during heating (Mocanu et al, 2018), it was suggested that the occurrence of the first tanδ maximum could be a composed effect of overlapping α -(bcc) →γ (fcc) reverse martensitic transformation and antiferromagnetic → paramagnetic transition at Néel temperature (T N ) (Pricop et al, 2018). At 50_MA specimens, the main diffraction maxima of martensite are more prominent than in the case of 0_MA, in good agreement with the micrographs from Figure 5.…”

Section: Thermomechanical Processing and Pre-straining Effectssupporting

confidence: 79%

“…By means of simultaneous thermal analysis (STA), powder mixtures of Fe-14Mn-6Si-9Cr-5Ni, were subjected to three heating-cooling cycles, between RT and 400 • C, under two FIGURE 4 | SEM micrographs illustrating sintering effects on 0_MA_700 specimen: (a) brittle general fractographic aspect with detail of an area with Zn stearate segregation; (b) magnified view of an area with connection bridges between deformed powder grains (reproduced after Mocanu et al, 2018, with permission granted by Springer Nature).…”

Section: Processing Procedures and Structure Of P/m-ma'ed Femnsicrni mentioning

confidence: 99%

“…shows long crack ribs and an area with Zn stearate segregation. Figure 4b displays the presence of connection bridges between elongated powder grains, as an effect of rolling (Mocanu et al, 2018).…”

Section: Figure 4amentioning

confidence: 99%

“…The evolution of a lamellar 40_MA_1000 specimen, containing 46.8% α -bcc and 25.5% ε-hcp martensite, is illustrated in Figure 13, during five training cycles (Mocanu et al, 2018). FIGURE 14 | Details of the training procedure applied to a 50_MA pipe-coupling ring subjected to free recovery SME, with opposite gray horizontal arrows indicating diameter shrinkage and blue tilted arrow emphasizing free-end displacement, from initial (I) to final (F) stages and variations of diameter and free-end displacement, during heating (modified after Bujoreanu, 2015).…”

Section: Shape Memory Effect and Applicationsmentioning

confidence: 99%

“…The evolution of the training parameters: T-temperature increase, t-maximum heating time, h-maximum vertical displacement, and average displacement rates in time ( h/ t) and with temperature ( h/ T) are summarized in Table 1, for the five cycles. In Figure 13b, during heating up to 236 • C, in the 5th cycle, the free end reached the position designated h 236 , which gives a total displacement h 5 = 24 mm and an average displacement rate of 1.71 mm/s (Mocanu et al, 2018).…”

Section: Shape Memory Effect and Applicationsmentioning

confidence: 99%

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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: 79%

Section: Processing Procedures and Structure Of P/m-ma'ed Femnsicrni mentioning

confidence: 99%

Section: Figure 4amentioning

confidence: 99%

Section: Shape Memory Effect and Applicationsmentioning

confidence: 99%

Section: Shape Memory Effect and Applicationsmentioning

confidence: 99%

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Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

et al. 2020

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Influence of Thermal and Mechanical/Powder Processing on Microstructure and Dynamic Stiffness of Fe-Mn-Si-Cr-Ni Shape Memory Alloy

Pricop

Borza

Özkal

et al. 2021

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On the Possible Cause of Sudden Storage Modulus Increase during the Heating of PM FeMnSiCrNi SMAs

et al. 2022

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A sudden increase in storage modulus (ΔE′) was repeatedly recorded during the heating of powder metallurgy (PM) 66Fe-14Mn-6Si-9Cr-5Ni (mass. %) shape memory alloy specimens subjected to dynamic mechanical analysis (DMA), under constant applied strain amplitude and frequency. This instability, exceeding 12 GPa, was associated with the reverse martensitic transformation of α′-body centered cubic (bcc) martensite to γ-face centered cubic (fcc) austenite, overlapped on a magnetic transition. This transition, observed by thermomagnetic measurements (T-MAG), was associated with the temporary spontaneous alignment of magnetic spins, which lasted until thermal movement became prevalent, during heating. ΔE′ was located around 250 °C on DMA thermograms and this temperature had the tendency to increase with the solution treatment temperature. On T-MAG diagrams, magnetization saturation temperature decreased from 405 °C to 52 °C with the increase in applied magnetic field from 20 Oe to 1 kOe and the increase in mechanically alloyed powder volume from 20% to 40%. On scanning electron micrographs, the presence of thermally induced α’-bcc martensite was emphasized together with the sub-bands that impede its stress-induced formation during DMA solicitation. On X-ray diffraction patterns of the solution-treated specimens, the presence of 22–82% α′-bcc martensite was identified, together with 8–55% retained austenite. It was assumed that the pre-existence of austenite together with α’-bcc martensite, in the microstructure of the solution-treated specimens, favored the magnetic transition, which destabilized the material and caused the storage modulus increase. The specimen comprising the largest amounts of austenite experienced the largest ΔE′.

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The Influence of α′ (bcc) Martensite on the Dynamic and Magnetic Response of Powder Metallurgy FeMnSiCrNi Shape Memory Alloys

Cited by 4 publications

References 32 publications

Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

Powder Metallurgy: An Alternative for FeMnSiCrNi Shape Memory Alloys Processing

Influence of Thermal and Mechanical/Powder Processing on Microstructure and Dynamic Stiffness of Fe-Mn-Si-Cr-Ni Shape Memory Alloy

On the Possible Cause of Sudden Storage Modulus Increase during the Heating of PM FeMnSiCrNi SMAs

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