Influence of Grain Size on Mechanical Properties of a Refractory High Entropy Alloy under Uniaxial Tension

Deluigi, Orlando; Valencia, Felipe J.; Tramontina, Diego; Amigó, Nicolás; Rojas-Nunez, Javier; Bringa, Eduardo M.

doi:10.3390/cryst13020357

Cited by 8 publications

(5 citation statements)

References 88 publications

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“…In experiment, 8 , 74 twinning was detected in deformation of HfNbTaTiZr for temperatures lower than 873 K; twinning at large shear strain has also been reported for the same EAM potential used here 9 , and twins under tension were found for simulations of HfNbTaZr when a void was present 67 , and for nanocrystalline samples 72 . However, Hu et al do not observe twinning under the high applied stress through direct impact Hopkinson bar test and compression strain 75 .…”

Section: Resultssupporting

confidence: 74%

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Nanoindentation into a bcc high-entropy HfNbTaTiZr alloy—an atomistic study of the effect of short-range order

Alhafez,

Deluigi,

Tramontina

et al. 2024

Sci Rep

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The plastic response of the Senkov HfNbTaTiZr high-entropy alloy is explored by means of simulated nanoindentation tests. Both a random alloy and an alloy with chemical short-range order are investigated and compared to the well understood case of an elementary Ta crystal. Strong differences in the dislocation plasticity between the alloys and the elementary Ta crystal are found. The high-entropy alloys show only little relaxation of the indentation dislocation network after indenter retraction and only negligible dislocation emission into the sample interior. Short-range order—besides making the alloy both stiffer and harder—further increases the size of the plastic zone and the dislocation density there. These features are explained by the slow dislocation migration in these alloys. Also, the short-range-ordered alloy features no twinning plasticity in contrast to the random alloy, while elemental Ta exhibits twinning under high stress but detwins considerably under stress relief. The results are in good qualitative agreement with our current knowledge of plasticity in high-entropy alloys.

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Section: Resultssupporting

confidence: 74%

“…Such misidentification by CNA can occur also for atoms in cubic phases, within the naturally distorted HEA structures 76 . Amorphization, supported by the lack of structure in the pair correlation function, was found in nanocrystalline HfNbTaZr under tension, for 5 nm grain size 72 .…”

Section: Resultsmentioning

confidence: 92%

Nanoindentation into a bcc high-entropy HfNbTaTiZr alloy—an atomistic study of the effect of short-range order

Alhafez,

Deluigi,

Tramontina

et al. 2024

Sci Rep

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“…Finally, dislocation segments can be analyzed according to their screw- or edge-character. To this end, we determine the angle between the Burgers vector and the dislocation line vector of each dislocation segment; we denote a segment as ‘screw’ if the angle is , as ‘edge’ if it is , and as ‘mixed’ otherwise 46 . Figure 10 shows the fraction of screw and edge segments in the entire sample.…”

Section: Resultsmentioning

confidence: 99%

“…In order to extract the twinned regions, we use the orientation quaternions obtained from the Polyhedral Template Matching (PTM) filter 44 available in OVITO, and transform them to vectors in Rodrigues space 45 . We calculate the misorientation angle for each atom from the dot product between the Rodrigues vector of that atom at a given frame and the vector at the initial frame 46 . Plasticity, including twinning, dislocations and stacking faults, leads to rotations with greater than .…”

Section: Methodsmentioning

confidence: 99%

Simulated nanoindentation into single-phase fcc Fe$$_{x}$$Ni$$_{1-x}$$ alloys predicts maximum hardness for equiatomic stoichiometry

Alhafez

Deluigi

Tramontina

et al. 2023

Sci Rep

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We investigate by molecular dynamics simulation the mechanical behavior of concentrated alloys under nanoindentation for the special example of single-phase fcc Fe$$_{x}$$ x Ni$$_{1-x}$$ 1 - x alloys. The indentation hardness is maximum for the equiatomic alloy, $$x=0.5$$ x = 0.5 . This finding is in agreement with experimental results on the strength of these alloys under uniaxial strain. We explain this finding with the increase of the unstable stacking fault energy in the alloys towards $$x=0.5$$ x = 0.5 . With increasing Fe content, loop emission from the plastic zone under the indenter becomes less pronounced and the plastic zone features a larger fraction of screw dislocation segments; simultaneously, the length of the dislocation network and the number of atoms in the stacking faults generated in the plastic zone increase. However, the volume of twinned regions in the plastic zone is highest for the elemental solids and decreases for the alloys. This feature is explained by the fact that twinning proceeds by the glide of dislocations on adjacent parallel lattice planes; this concerted motion is less efficient in the alloys. Finally, we find that surface imprints show increasing pile-up heights with increasing Fe content. The present results will be of interest for hardness engineering or generating hardness profiles in concentrated alloys.

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“…It is well known that some parameters, such as the incorporation of binders [ 40 ], porosity [ 41 ], grain size [ 42 , 43 ], or density [ 44 ], strongly affect the mechanical behavior of the final materials. For this reason, before the study of the mechanical properties of the composites, the bulk and real density, together with the total porosity, were measured for all the samples (shown in Table 3 ), as well as the morphology of the composites by means of SEM.…”

Section: Resultsmentioning

confidence: 99%

Improved Thermophysical and Mechanical Properties in LiNaSO4 Composites for Thermal Energy Storage

Taeño,

Adnan,

Luengo

et al. 2023

Nanomaterials

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Solid-solid phase-change materials have great potential for developing compact and low-cost thermal storage systems. The solid-state nature of these materials enables the design of systems analogous to those based on natural rocks but with an extraordinarily higher energy density. In this scenario, the evaluation and improvement of the mechanical and thermophysical properties of these solid-solid PCMs are key to exploiting their full potential. In this study, LiNaSO4-based composites, comprising porous MgO and expanded graphite (EG) as the dispersed phases and LiNaSO4 as the matrix, have been prepared with the aim of enhancing the thermophysical and mechanical properties of LiNaSO4. The characteristic structure of MgO and the high degree of crystallinity of the EG600 confer on the LiNaSO4 sample mechanical stability, which leads to an increase in the Young’s modulus (almost three times higher) compared to the pure LiNaSO4 sample. These materials are proposed as a suitable candidate for thermal energy storage applications at high temperatures (400–550 °C). The addition of 5 wt.% of MgO or 5% of EG had a minor influence on the solid-solid phase change temperature and enthalpy; however, other thermal properties such as thermal conductivity or specific heat capacity were increased, extending the scope of PCMs use.

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Influence of Grain Size on Mechanical Properties of a Refractory High Entropy Alloy under Uniaxial Tension

Cited by 8 publications

References 88 publications

Nanoindentation into a bcc high-entropy HfNbTaTiZr alloy—an atomistic study of the effect of short-range order

Nanoindentation into a bcc high-entropy HfNbTaTiZr alloy—an atomistic study of the effect of short-range order

Simulated nanoindentation into single-phase fcc Fe$$_{x}$$Ni$$_{1-x}$$ alloys predicts maximum hardness for equiatomic stoichiometry

Improved Thermophysical and Mechanical Properties in LiNaSO4 Composites for Thermal Energy Storage

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