Investigation on the maximum strain rate sensitivity ( m ) superplastic deformation of Mg-Li based alloy

Yang, Hui; Fu, Ming; To, Suet; Wang, G.C.

doi:10.1016/j.matdes.2016.09.066

Cited by 26 publications

(17 citation statements)

References 29 publications

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“…Furthermore, OCDs have been reported to improve the biostability of polyurethanes (PURs) when compared to those based on polyesters and polyethers, which is essential for purposes of long-term medical applications, we would like to achieve by our PCUU system. [13][14][15][16][17][18][19][20][21] In the first step, the OCDs were functionalized with an excess of diisocyanate to obtain diisocyanate telechelics. Afterwards, a moisture-curing process, [22,23] in which water vapors were added to hydrolyze the isocyanate to amine groups, was applied.…”

Section: Introductionmentioning

confidence: 99%

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Mazurek-Budzyńska

Razzaq

Tomczyk

et al. 2016

Polymers for Advanced Techs

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A challenge in the design of shape‐memory polymers (SMPs) is to achieve high deformability with a simultaneous high shape recovery ratio. Here we explored, whether SMPs featuring large deformation capability and high shape recovery ratios can be created as polymer networks providing two kinds of netpoints based on covalent bonds and physical interactions. As a model system, we selected poly(carbonate‐urea‐urethane)s (PCUUs) synthesized by a precursor route, based on oligo(alkylene carbonate) diols, isophorone diisocyanate (IPDI), and water vapor. The PCUU networks exhibited a one‐way shape‐memory effect (1W‐SME) with programmed strains up to εprog = 1000% whereby they provided excellent shape fixity (92–97%) and shape recovery (≥99%) ratios. The switching temperatures (Tsw) varied between 36 and 65 °C and increased with the increasing molecular weight of the oligo(alkylene carbonate) diol and length of the hydrocarbon chain between the carbonate linkages. Tsw was also influenced by the strain applied during programming (εprog). Poly(carbonate‐urethane)s have been reported to have good biocompatibility and biostability, which in the combination of high‐strain capacity and high Young's modulus makes the obtained PCUUs interesting candidate materials suitable for medical devices such as medical sutures or vascular stents. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Mazurek-Budzyńska

Razzaq

Tomczyk

et al. 2016

Polymers for Advanced Techs

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“…Many crystal defects can be seen at the interface of both areas, indicating the important role of deformation in the formation of the hcp α phase within the β grains. Although the KOBO extrusion was performed at RT, an increase of temperature could not be excluded and one can assume that the formation of the hcp α phase was temperature assisted as suggested also in previous works [25,27,28,32], in which the elevated temperature deformation was applied. Figure 8 contains the SEM micrographs of the KOBO extruded samples deformed additionally with 20 forging cycles at 150 °C (a) and 200 °C (b).…”

Section: Resultsmentioning

confidence: 98%

“…The SADP from the dark area shows rather a complicated pattern that can be solved as a mixture of the bcc β phase of [001] zone axis orientation, the hcp α phase of [011 0] zone axis orientation and intermetallic phases formed due to the aluminum and scandium additions that were indexed as Al 3 Sc of [001] zone axis and LiMgAl 2 with the [014] zone axis. Comparing the microstructures of hcp α and bcc β phases, much more precipitates within the β phase were recorded due to higher Li and 1% Al [28] and in the dual phase Mg-Li-Al alloys after the ECAP or multiple forging SPD [25,32,35]. The origin of this phase is not well understood, however it may be possible that during severe plastic deformation, diffusion assisted α phase formation was initiated on frequent crystal defects within the β phase which as softer one carries most of sample deformation during either ECAP or KOBO processing and consequently the α phase particles form in the whole volume of β grains.…”

Section: Methodsmentioning

confidence: 99%

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Effect of KOBO Extrusion and Following Cyclic Forging on Grain Refinement of Mg–9Li–2Al–0.5Sc Alloy

et al. 2019

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KOBO type extrusion and following cyclic forging in two perpendicular directions at temperatures 150-200 °C were applied to new Mg-9Li-2Al-0.5Sc alloy to study its effect on strength and microstructure evolution. KOBO extrusion of as cast ingot caused significant grain refinement of (α + β) dual phase Mg-9Li-2Al-0.5Sc alloys down to range 1-10 μm for hcp α phase and 1-5 μm for the β phase as resulted from EBSD studies. At that stage ultimate tensile strength UTS of 168 MPa and elongation of 36% were attained. Additional deformation by cyclic forging alternatively from 2 perpendicular directions caused formation of much finer grains of average size of few hundred nm observed using TEM and close to 1 μm applying EBSD technique. Tensile strength increased after that operation above 200 MPa and elongation above 40%, which were the highest observed in the dual phase Mg-Li based alloys. Deformation by cyclic forging induced formation of strong texture with 0001 plane parallel to forging directions. Additional precipitates of size below 1 μm at α/β interfaces or within β phase were identified as hcp AlSc 2 phase. Fine particles of hcp α phase were observed after severe plastic deformation SPD within β phase grains, as effect of diffusion assisted deformation. The amount of hcp α phase increased after SPD up to 70% from initial 40%. High density of defects at α/β interfaces on 0001 planes observed in HRTEM mode was responsible for promotion of hcp phase formation during SPD.

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“…With the decrease of the initial strain rate both the amount and size of cavitations increased. There is only limited information on the role of the α and β phases during the deformation of Mg-Li based alloys, which possess different mechanical properties and often different grain sizes [6][7][8][9][10][11][12]. A small addition of other elements to binary Mg-Li alloys allows to improve the mechanical properties as well as helps to achieve strong grain refinement during deformation processes [6].…”

Section: Introductionmentioning

confidence: 99%

Superplastic deformation of Mg–9Li–2Al–0.5Sc alloy after grain refinement by KoBo extrusion and cyclic forging

Kalita

Maziarz

Faryna

2020

Archiv.Civ.Mech.Eng

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The quaternary Mg–9Li–2Al–0.5Sc alloy (in wt%) was prepared from pure components. After homogenization, the alloy was subjected to severe plastic deformation by KoBo extrusion and cyclic forging leading to grain refinement in the range of 0.5–2 µm of hexagonal close-packed (HCP) α phase. Deformed alloys showed high ultimate tensile strength near 200 MPa and good elongation in the range 30–40% at room temperature (RT). Large elongations close to 200% were obtained during the tensile test at a temperature of 200 °C. Deformed samples showed the presence of multiple voids confirming grain boundary sliding mechanism of deformation. Twins on {10$$\overline{1}$$ 1 ¯ 2} planes were identified using electron backscatter diffraction analysis, being in a good agreement with the earlier observation of Mg–Li and Mg–Sc alloys. Intermetallic phases such as cubic MgSc were identified in deformed alloys mostly within HCP α phase, whereas HCP MgSc2 particles were observed within body-centered cubic (BCC) β phase. Intermetallic phases were responsible for RT strengthening of alloys and slightly lower tensile elongation during superplastic deformation. Formation of the HCP α phase was observed within the BCC β phase in tensile deformed alloys. Atomic-level nucleation of HCP phase within the β phase was identified by the use of high-resolution transmission electron microscopy technique.

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Investigation on the maximum strain rate sensitivity ( m ) superplastic deformation of Mg-Li based alloy

Cited by 26 publications

References 29 publications

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Poly(carbonate‐urea‐urethane) networks exhibiting high‐strain shape‐memory effect

Effect of KOBO Extrusion and Following Cyclic Forging on Grain Refinement of Mg–9Li–2Al–0.5Sc Alloy

Superplastic deformation of Mg–9Li–2Al–0.5Sc alloy after grain refinement by KoBo extrusion and cyclic forging

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