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    Effect of hydrogen on the ideal shear strength in metals and its implications on plasticity: A first-principles study
    (21-07-2021)
    Kumar, P.
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    Garg, P.
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    Solanki, K. N.
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    Hydrogen embrittlement limits the service life of various metallic components by causing a transition from a ductile to a brittle failure of inherently ductile alloys. In this work, using first-principles calculations, the effect of interstitial hydrogen on the ideal shear strength across various metals (Al, Ni, Fe, Nb, Ti, and Zr) and its implications on plasticity are discussed. The presence of hydrogen led to a volumetric expansion, which in turn had a key role in the observed shear strength response of cubic metals. However, in the case of HCP metals, the chemical contributions also have a significant part in the observed shear strength response. The interstitial hydrogen atom interacts strongly with valence d orbital metals (Ni, Fe, Nb, Ti, and Zr). Based on the Peierls-Nabarro framework, the presence of interstitial hydrogen reduces the Peierls stress across all the metals examined here. Finally, these findings provide insights to comprehensively understand hydrogen embrittlement.
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    Effect of hydrogen on plasticity of α-Fe: A multi-scale assessment
    (01-06-2023)
    Kumar, Pranav
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    Ludhwani, Mohit M.
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    Das, Sambit
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    Gavini, Vikram
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    A multi-scale study was carried out to quantify the effect of interstitial hydrogen concentration on plasticity in α-Fe. In this work, the influence of hydrogen on the screw dislocation glide behavior was examined across several length-scales. The insights obtained were integrated to provide an accurate continuum description for the effect of hydrogen on the dislocation based plasticity in polycrystalline α-Fe. At the outset of this work, a new Fe[sbnd]H interatomic potential was formulated that enhanced the atomistic estimation of the variation in dislocation glide behavior in presence of hydrogen. Next, the dislocation core reconstruction observed due to the addition of hydrogen using atomistic simulations was validated with the help of large-scale DFT calculations based on the DFT-FE framework. Several atomistic simulations were carried out to comprehensively quantify the effect of hydrogen on the non-Schmid behavior exhibited during the dislocation glide in α-Fe. Finally, crystal plasticity simulations were carried out to understand the effect of hydrogen on the meso-scale deformation behavior of polycrystalline α-Fe.
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    Publication
    Effect of interstitial hydrogen on elastic behavior of metals: An ab-initio study
    (01-01-2023)
    Kumar, P.
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    A comprehensive assessment of interstitial hydrogen on the elastic behavior across different metals (Al, Ni, Fe, Nb, Ti, and Zr) was carried out using first-principles calculations. The volumetric strain introduced by interstitial hydrogen had a key role in the observed variation in elastic constants. However, in Nb, Ti, and Zr, the host and hydrogen atoms interact strongly which had a significant contribution towards the variation in elastic response due to the presence of hydrogen. The addition of hydrogen reduced the resistance to shear deformation along respective active slip systems for all the metals, except Nb. Similarly, the homogenized macroscopic approximation of Young's and shear moduli also demonstrated a drop with increasing hydrogen concentration across all the metals, apart from Nb. Finally, these findings accurately quantify the variation in elastic behavior of various metals when exposed to a hydrogen rich environment.