Microstructure and mechanical properties of a Cu-Zr based bulk metallic glass containing atomic scale chemical heterogeneities

Rashidi, Reza; Malekan, Mehdi; Gholamipour, Reza

doi:10.1016/j.msea.2018.05.082

Cited by 31 publications

(3 citation statements)

References 35 publications

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“…Among other glass-forming metallic alloys the Cu-Zr-based ones are of the greatest importance due to their high glass-forming ability [45][46][47][48], relatively simple and cheap fabrication and possibility to form highstrength ductile BMG composites [49][50][51]. Besides, simulated Cu-Zr-based systems are widely accepted as models demonstrating pronounced icosahedral local ordering [33][34][35][36][37][38][39]41].…”

Section: Introductionmentioning

confidence: 99%

Nucleation instability in supercooled Cu–Zr–Al glass-forming liquids

Ryltsev

Klumov

Chtchelkatchev

et al. 2018

The Journal of Chemical Physics

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Special role in computer simulations of supercooled liquid and glasses is played by few general models representing certain classes of real glass-forming systems. Recently, it was shown that one of the most widely used model glassformers -Kob-Andersen binary Lennard-Jones mixture -crystalizes in quite lengthy molecular dynamics simulations and, moreover, it is in fact a very poor glassformer at large system sizes. Thus, our understanding of crystallization stability of model glassformers is far from complete due to the fact that relatively small system sizes and short timescales have been considered so far. Here we address this issue for two embedded atom models intensively used last years in numerical studies of Cu-Zr-(Al) bulk metallic glasses. We consider Cu64.5Zr35.5 and Cu46Zr46Al8 alloys as those having high glass-forming ability. Exploring their structural evolution at continuous cooling and isothermal annealing, we observe that both systems nucleate in sufficiently lengthy simulations, though Cu46Zr46Al8 demonstrate order of magnitude higher critical nucleation time. Moreover, Cu64.5Zr35.5 is actually unstable to crystallization for large system sizes (N > 20, 000). Both systems crystallize with the formation of tetrahedrally close packed Laves phases of different types. We reveal that structure of both systems in liquid and glassy state contains comparable amount of polytetrahedral clusters. We argue that nucleation instability of simulated Cu64.5Zr35.5 alloy is due to the fact that its composition is very close to that for stable Cu2Zr compound with C15 Laves phase structure. arXiv:1809.00198v1 [cond-mat.mtrl-sci] 1 Sep 2018

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Section: Introductionmentioning

confidence: 99%

Nucleation instability in supercooled Cu–Zr–Al glass-forming liquids

Ryltsev

Klumov

Chtchelkatchev

et al. 2018

The Journal of Chemical Physics

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“…A dispersion of a second phase in an MG matrix must affect the operation of SBs in an MG, but in the same way as for monolithic MGs (Extended Data Table 1) we consider any SB activity to be incompatible with true strain-hardening of the MG. Key observations [29][30][31][32][33][34][35][36][37][38] (all at room temperature) are listed in the table. Strain-hardening of composites in tension is clearly associated with transformationinduced hardening of a dispersed crystalline phase that is sufficient to outweigh the softening of the MG matrix.…”

Section: Data Availabilitymentioning

confidence: 99%

Strain-hardening and suppression of shear-banding in rejuvenated bulk metallic glass

Pan

Ivanov

Zhou

et al. 2020

Nature

248

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Strain-hardening (the increase of flow stress with plastic strain) is the most important phenomenon in the mechanical behaviour of engineering alloys because it ensures that flow is delocalized, enhances tensile ductility and inhibits catastrophic mechanical failure 1,2. Metallic glasses (MGs) lack the crystallinity of conventional engineering alloys, and some of their properties-such as higher yield stress and elastic strain limit 3-are greatly improved relative to their crystalline counterparts. MGs can have high fracture toughness and have the highest known 'damage tolerance' (defined as the product of yield stress and fracture toughness) 4 among all structural materials. However, the promise of MGs for structural applications is largely thwarted by the fact that they show strain-softening, instead of strain-hardening; this leads to extreme localization of plastic flow in shear bands, and is associated with early catastrophic failure in tension. Although rejuvenation of an MG (raising its energy to values that are typical of glass formation at a higher cooling rate) lowers its yield stress, which might enable strain-hardening 5 , it is unclear whether sufficient rejuvenation can be achieved in bulk samples while retaining their glassy structure. Here we show that plastic deformation under triaxial compression at room temperature can rejuvenate bulk MG samples sufficiently to enable strain-hardening through a mechanism that has not been previously observed in the metallic state. This transformed behaviour suppresses shear-banding in bulk samples in normal uniaxial (tensile or compressive) tests,

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“…Figure 6(a,c,e) respectively show SEM images of the lateral surface for (Cu 0.47 Zr 0.47 Al 0.06 ) 99 Ni 1 , (Cu 0.47 Zr 0.47 Al 0.06 ) 98.5 Ni 1 Nb 0.5 and (Cu 0.47 Zr 0.47 Al 0.06 ) 98 Ni 1 Nb 1 compressive samples after fracture. It has been demonstrated that the crystalline particles embedded in the glassy matrix can hinder the propagation of SBs and result in the deflection and numerous formation of SBs, thus, the plasticity of the composites can be accommodated by the formation of extensive SBs as well as their multiplication and interaction [23,24]. For the Nb-free sample, though a large volume fraction of the B2-CuZr phase is embedded in the glassy matrix, only a few SBs and its multiplication marked by the white circle in Figure 6(a) are detected on the lateral surface.…”

Section: Resultsmentioning

confidence: 99%

Microstructure evolution and mechanical properties of Nb-alloyed Cu–Zr–Al–Ni large-sized metallic glass composites

Shao

Aisheng

Wang

2019

Materials Science and Technology

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The effects of Nb on the microstructures and mechanical properties of large-sized (Cu0.47Zr0.47Al0.06)99 − xNi1Nb x ( x = 0, 0.5, 1, 2 at.-%) bulk metallic glass composites were investigated. It is verified that the liquidus temperature ( Tl) of the Nb-added alloys decreases to cause the increase of glass-forming ability (GFA). The addition of Nb adjusts the distribution and the volume fraction of B2-CuZr phase in the Cu–Zr–Al–Ni large-sized composites by changing the GFA of the alloys. The mechanical properties of the composites strongly depend on the volume fraction and distribution of B2-CuZr phase in the glassy matrix. The alloy with 0.5 at.-% Nb addition exhibits the high mechanical properties, which should be attributed to the uniform distribution and the proper volume fraction of B2-CuZr phase in the glassy matrix.

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Microstructure and mechanical properties of a Cu-Zr based bulk metallic glass containing atomic scale chemical heterogeneities

Cited by 31 publications

References 35 publications

Nucleation instability in supercooled Cu–Zr–Al glass-forming liquids

Nucleation instability in supercooled Cu–Zr–Al glass-forming liquids

Strain-hardening and suppression of shear-banding in rejuvenated bulk metallic glass

Microstructure evolution and mechanical properties of Nb-alloyed Cu–Zr–Al–Ni large-sized metallic glass composites

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