Browsing by Author "Mohanty, H."

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Annealing-induced changes in wear resistance and nanomechanical properties of CuZr metallic glass thin films
(Institute of Physics, 2023) Gao, J.; He, N.; Rathan, A.; Kumar Agrawal, M.K.; Mohanty, H.
Over recent years, metallic glass thin films (MGTFs) have found extensive applications in advanced micro-engineering systems. Consequently, there is a need to thoroughly assess the nanomechanical and tribological behaviors of MGTFs to optimize the design of efficient components. In this study, we employed the nanoindentation technique in various modes to investigate the elastic heterogeneity, tribological response, and mechanical properties of CuZr amorphous films. Before conducting the mechanical tests, annealing treatments at 500 K and 600 K were performed to create samples with different stored energies. The thermal history analysis revealed that the annealing process reduced the stored energy in the microstructure. Furthermore, the pre-annealing treatment resulted in increased hardness and Young’s modulus of the thin films. Additionally, higher annealing temperatures significantly improved the wear resistance of the MGTFs. Observing the serration dynamics in the scratching test, we noticed that the annealing treatment induced larger shear bands on the wear track side. Moreover, the increase in annealing temperature led to a reduction in elastic heterogeneity, which was consistent with the enthalpy relaxation values in the samples. This suggests that the annealing temperature enhanced the densely packed atomic structure, leading to the stabilization of the thin films. © 2023 The Author(s). Published by IOP Publishing Ltd.
Characterizing Structural Heterogeneity in Metallic Glasses: A Molecular Dynamics-Guided Machine Learning Approach
(Springer, 2024) Li, H.; Mohanty, H.
The main objective of this research is to develop a robust Bayesian machine learning (ML) model capable of predicting and characterizing the structural heterogeneity in metallic glasses (MGs). The model is constructed using input data obtained from molecular dynamics simulations of CuZr MGs, encompassing a wide range of alloying compositions and simulation parameters. The ML model utilized crucial output variables: the 2D fractal dimension (with a fractal exponent ranging from 1.55 to 1.81) and correlation function (correlation length spanning from 1.1 to 4.05 nm), demonstrating inverse and direct relationships with the degree of heterogeneity, respectively. The results demonstrate the model's high predictive performance, with accuracy values of 0.9398 for the fractal dimension and 0.9639 for the correlation length. It is noteworthy that the correlation length proves to be a reliable indicator for low to intermediate levels of structural heterogeneity, while the fractal dimension effectively characterizes high-level heterogeneity in MGs. Moreover, the integration of both indicators complements each other in accurately predicting structural heterogeneity. Additionally, the developed ML model showcases its versatility in effectively characterizing MG samples exposed to diverse treatments, such as annealing and rejuvenation processes. © The Indian Institute of Metals - IIM 2023.
Role of initial stored energy on hydrogen microalloying of ZrCoAl(Nb) bulk metallic glasses
(Springer Science and Business Media Deutschland GmbH, 2021) Sharaf, H.K.; Salman, S.; Abdulateef, M.H.; Magizov, R.R.; Troitskii, V.I.; Mahmoud, Z.H.; Mukhutdinov, R.H.; Mohanty, H.
In this paper, the role of primary stored energy and structural heterogeneity on the subsequent effects of hydrogen microalloying in glassy alloys was studied. For this purpose, two bulk metallic glasses with different chemical compositions and initial stored energy, i.e. Zr60Co30Al10 and Zr55Co30Al10Nb5, were fabricated in a hydrogen-induced environment. Dynamic mechanical analysis and nanoindentation tests were carried out to evaluate relaxation behavior and mechanical properties of bulk metallic glasses, respectively. The nanoindentation results indicated declining serrations in load–displacement curves of hydrogen-affected samples. This event was related to the annihilation of localized deformation in hydrogen-affected samples under the external load. Moreover, the dynamic mechanical analysis showed that the hydrogen microalloying process improved the plasticity behavior of metallic glasses by activating fast ?? relaxation. Finally, the results unveiled that the higher initial structural heterogeneity and stored energy in the bulk metallic glass with the alloying composition of Zr55Co30Al10Nb5 led to the improvement of microalloying effects on the corresponding properties. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.