Heterogeneous nucleation at inoculant particles in a glass forming alloy: An ab initio molecular dynamics investigation of interfacial properties and local chemical bonding

Mahjoub, Reza; Xu, Weitao; Gun, B.; Laws, Kevin J.; Kong, Lingti; Li, J.F.; Ferry, Michael

doi:10.1016/j.commatsci.2015.06.008

Cited by 10 publications

(3 citation statements)

References 44 publications

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“…18 At higher temperatures, there is an increase in both the atomic displacements and the number of atoms participating in the jumps. 21 It is pertinent to note that, although crystallisation is universally known to be a first-order thermodynamic transformation, 22,23 glass transition has been prevailingly considered as a largely dynamical phenomenon 24 and soft phonons are known to be related to the dynamics of amorphous alloys. 18,25 Although the energy landscape curvature and mean-squared atomic displacements (MSD) are two different quantities, they are inter-connected often in complicated relations.…”

Section: Resultsmentioning

confidence: 99%

Softening of phonon spectra in metallic glasses

et al. 2016

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The vibrational spectra of a series of MgZnCa amorphous alloys were computed using density functional theory and implementing the small displacement method. The atomic structures of the alloys were obtained by ab initio molecular dynamics simulations. The vibrational thermodynamic properties were calculated as a function of temperature and, in particular, the specific heat at low temperature was approximated by temperature cubed based on the Debye model. We computed the contribution of Mg vibrations to the specific heat and investigated the softening of Mg phonon spectra, where the maximum allowed vibrational frequency is lowered and highly collective diffusion processes are promoted. The statistical correlation between the reported critical casting thickness of the alloys and softening of Mg phonons was obtained. Similar calculations were performed for two distinctively different amorphous ZrTiCuAl alloys with large and small reported critical casting thickness, respectively. The findings were consistent with those of the MgZnCa alloys. INTRODUCTIONThere has been increasing attention devoted to the effect of vibrational thermodynamics on the formation of different alloy phases and their associated phase transformations due to the improved accessibility of instruments capable of measuring and calculating the phonon frequencies. 1 Various thermodynamic properties such as specific heat and vibrational entropy can be derived through the vibrational density of states (VDOSs). The VDOS obtained by molecular dynamics (MD) simulations has provided useful insight into how phonon spectra are affected by both the size and surface properties of silicon nanoparticles; this is of major significance in the design of nanodevices with better heat transport properties. It was found that, as the Si particles become smaller, the density of vibrational states increases at low frequencies, and modes are transferred from the high-frequency end to the intermediate range and transverse optical modes peak are shifted to higher frequencies. 2 In metallic glasses, vibrational characteristics have also been used for explaining mechanical properties. For example, recent MD simulations of a Cu 64 Zr 36 metallic glass showed that the strongest participation in the modes with lowest vibrational frequency and, hence, weakest spring constants (i.e., soft modes) originate predominantly from meagrely populated polyhedra. These soft spots provide fertile sites for accommodating shear transformations. 3 The softening of long wavelength acoustic phonons in PdSiCu, ZrTiCuNiBe, CeAlNiCu and ZrNbCuNiBe amorphous alloys relative to their crystalline phases have been observed experimentally using ultrasound measurements. [4][5][6] Such observations are consistent with the low-temperature measurements of their specific heat, whereby an increase in temperature causes a steeper increase in specific heat in the amorphous alloys compared with their crystalline counterparts.Specific heat is believed to be a fundamental property of materials and, in particular,...

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Section: Resultsmentioning

confidence: 99%

Softening of phonon spectra in metallic glasses

et al. 2016

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“…One parameter which did highlight the differences that solutes imposed on the boundaries was the Work of Separation, W SEP . This parameter has traditionally been used [29,36] to examine the cohesion of a boundary, as it indicates the work required to separate two neighbouring grains. However, in the present case we use W SEP as a tool to identify the changes that occur when solute is located at the boundary.…”

Section: Effect Of Solutesmentioning

confidence: 99%

The Energetics and Topology of Grain Boundaries in Magnesium: An Ab Initio Study

Mahjoub

Stanford

2022

Alloys

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First principles calculations were carried out on six different grain boundaries with complex, non-symmetrical, crystallography’s. Solute species (Gd and Zn) were placed in multiple locations to investigate their effect on the boundary energetics. The grain boundaries were found to have an intrinsic grain boundary energy, and this energy was not markedly affected by the solute concentration at the boundary. However, the work of separation (WSEP) was very sensitive to grain boundary chemistry. Boundaries of higher disorder were found to be more sensitive to boundary chemistry and showed higher values of WSEP and in the case of Gd, were more sensitive to solute concentration at the boundary. No correlation between the boundary behaviour and crystallography could be found, apart from the over-riding conclusion that all six boundaries showed markedly different behaviours, and the effect of solute on each were unique.

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“…Ceramics such as ZrC, SiC, and carbon fibers are often used as inoculants. Previously [9,10], such inoculation has been shown to increase the ductility and facture toughness of BMG composites. However, the liquid-to-crystalline phase transformation is still not very well understood.…”

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confidence: 99%

Understanding Microstructural Evolution in ZrC Inoculated Zr_47.5Cu_45.5Al₅Co₂ Via High Resolution SIMS

Lewis¹,

Rafique

Khanom³

2019

Microsc Microanal

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Heterogeneous nucleation at inoculant particles in a glass forming alloy: An ab initio molecular dynamics investigation of interfacial properties and local chemical bonding

Cited by 10 publications

References 44 publications

Softening of phonon spectra in metallic glasses

Softening of phonon spectra in metallic glasses

The Energetics and Topology of Grain Boundaries in Magnesium: An Ab Initio Study

Understanding Microstructural Evolution in ZrC Inoculated Zr_47.5Cu_45.5Al₅Co₂ Via High Resolution SIMS

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Heterogeneous nucleation at inoculant particles in a glass forming alloy: An ab initio molecular dynamics investigation of interfacial properties and local chemical bonding

Cited by 10 publications

References 44 publications

Softening of phonon spectra in metallic glasses

Softening of phonon spectra in metallic glasses

The Energetics and Topology of Grain Boundaries in Magnesium: An Ab Initio Study

Understanding Microstructural Evolution in ZrC Inoculated Zr47.5Cu45.5Al5Co2 Via High Resolution SIMS

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Understanding Microstructural Evolution in ZrC Inoculated Zr_47.5Cu_45.5Al₅Co₂ Via High Resolution SIMS