Journal of Materials Science

Khraishi, Tariq; Ayoub, Georges; Mesarovic, Sinisa; Shehadeh, Mutasem

doi: 10.1007/s10853-024-09584-7pmid: N/A

Hasan, Md Mahmudul; Srinivasan, Srivilliputhur G.; Choudhuri, Deep

doi: 10.1007/s10853-023-09078-ypmid: N/A

Several high-temperature body-centered cubic (bcc) structural materials such as Nb-, Zr- and Ti-based alloys undergo phase separation, which is a second-order phase transformation, whereby the host lattice decomposes into distinct bcc domains with different compositions. Using atomistic simulations, we studied the high-strain-rate response of bcc-forming Nb–xZr (x = 0, 25, 50 at.%) alloys. To induce phase separation in our starter alloy, we first employed hybrid Monte Carlo/Molecular Dynamics simulations in single crystals of Nb–xZr at 1000 K. Subsequently, these crystals were deformed along different crystallographic orientations (⟨001⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 001\rangle$$\end{document}, ⟨110⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 110\rangle$$\end{document} and ⟨111⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 111\rangle$$\end{document}) at a strain rate of 10+8s-1\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$10^{+8} s^{-1}$$\end{document}, to investigate orientation dependent mechanical response. The phase-separated Nb–xZr microstructures exhibited distinct bcc domains enriched in either Zr or Nb. Notably, Nb-50 at.%Zr contained coarser Zr-domains compared to Nb-25 at.%Zr. The Zr-rich domains acted as “soft” inclusions, resulting in reduced peak strengths in the following order: pure Nb (Nb-0 at.%Zr) > Nb-25 at.%Zr > Nb-50 at.%Zr. This implies that phase separation causes softening in Nb–xZr. We also discovered two deformation pathways that depended on the crystallographic orientation: (i) For deformation along ⟨110⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 110\rangle$$\end{document} and ⟨111⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 111\rangle$$\end{document} directions: Elastic deformation was followed by dislocation plasticity on {110}⟨111⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\{110\}\langle 111\rangle$$\end{document} slip systems; and (ii) For deformation along ⟨001⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 001\rangle$$\end{document} direction: Elastic deformation was followed by the formation of a volumetric fcc structure, twinning on {112}⟨111⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 111\rangle$$\end{document} system, and the formation fcc-phase at the twin/matrix interfacial regions. This was ultimately accompanied by dislocation plasticity on {110}⟨111⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\{110\}\langle 111\rangle$$\end{document} slip system. The bcc→\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\rightarrow$$\end{document}fcc displacive transformation facilitated {112}⟨111⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 111\rangle$$\end{document} twinning when Nb–xZr was deformed along ⟨001⟩\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\langle 001\rangle$$\end{document}. Our investigation shows that softening of bcc alloys can result from a coupling of mechanisms involving local solute segregation, displacive phase transformation and twinning occurring across multiple slip planes.

Wang, Wenbo; Izadi, Sina; Mraied, Hesham; Deng, Chuang; Cai, Wenjun

doi: 10.1007/s10853-023-08908-3pmid: N/A

Hardness of nanostructured metallic multilayers (NMMs) are often understood from their dependence on individual layer thickness (h), yet little is known about the impacts exerted by other microstructural factors. In this work, the effects of residual stress and interface coherency on the deformation mechanisms of Al/Ti NMMs with h = 2.5–52 nm were studied via experiments and molecular dynamics simulations. The residual stress was found to be tensile in Ti layers and compressive in Al layers in general, both of which tended to increase with decreasing h. Tensile stress of more than 2 GPa were measured in the Ti layers at h < 10 nm. Such high stress was related to the more coherent interfaces at small h, as confirmed by transmission electron microscopy analysis. Finally, molecular dynamics simulations showed that at h = 2.5 nm, the coherent interfaces were more effective barriers to dislocation initiation and transfer than the incoherent ones.

Uddin, Md Mesbah; Salehinia, Iman

doi: 10.1007/s10853-023-08867-9pmid: N/A

Molecular dynamics atomistic simulations were used to investigate the tribological properties of NbC/Nb ceramic/metal nano-laminates (CMNLs) during nano-indentation and nano-scratching. The study compared the scratching behavior of the CMNLs to that of NbC and Nb single crystals. Two CMNL models were considered, both featuring a top layer of NbC with differing metallic layer thicknesses of 2 nm and 8 nm. Spherical indenters with radii of 5, 10, and 20 nm were used to scratch the CMNLs with a 3 nm penetration depth, avoiding penetration into the metallic layer beneath the ceramic layer. The results revealed that the alternating metallic and ceramic layers in the CMNL models reduced the amount of material removed during scratching compared to NbC single crystals. The model with the thickest metallic layer showed lower friction coefficient and material removal. The simulations demonstrated that the indenter size had a significant effect on the scratch behavior of CMNLs, with the friction coefficients for the larger indenters being notably lower. The study revealed that larger indenters show less sensitivity to the individual layer thickness in terms of friction coefficients and material removal. The scratching response of the models was linked to the atomic-level deformation mechanisms during the scratching process. The dominant factors affecting the scratching behavior were individual layer thickness, indenter size, and the scratching attack angle. Overall, the study provides valuable insights into the tribological behavior of CMNLs and sheds light on the design of scratch-resistant coatings.

Ji, Weisen; Jian, Wu-Rong; Su, Yanqing; Xu, Shuozhi; Beyerlein, Irene J.

doi: 10.1007/s10853-023-08779-8pmid: N/A

Metallic nanolaminates exhibit superior strength compared to their coarsely laminated counterparts. For layer thicknesses in the range of a few to tens of nanometers, the strength of these materials is related to the stress required for individual dislocations to thread through the nanometer-thick layers, a motion called confined layer slip (CLS). Here, using atomistic simulations, we model the CLS in nanolaminated Cu with incoherent interfaces, with a focus on the role of stacking fault energies (SFEs), which are varied by up to one order of magnitude while other material parameters are largely kept the same. Our simulations found that (i) the intrinsic SFE affects the structures of both the dislocation core and the interfaces and (ii) the critical stress for CLS scales positively with the energy of the incoherent interface, but negatively with the ratio between the intrinsic SFE and the unstable SFE.

Aquistapace, Franco; Castillo-Castro, Daniel; González, Rafael I.; Amigo, Nicolás; García Vidable, Gonzalo; Tramontina, Diego R.; Valencia, Felipe J.; Bringa, Eduardo M.

doi: 10.1007/s10853-023-09223-7pmid: N/A

This work focuses on the mechanical response of cubic-diamond nanoparticles of several sizes when subjected to a planar indenter. Three sequential stages were considered, i.e., loading, unloading, and reloading. In the large anisotropic strain regime, standard structure detectors stop identifying atoms as having diamond structures, affecting the ability to detect dislocations. A machine learning-assisted structure detector, MultiSOM, is able to detect a significantly larger number of crystalline diamond atoms and also identify much larger dislocation densities. MultiSOM also detects a distorted diamond phase and directional amorphization, similar to what has been observed for other covalent solids at high strain. After unloading, there is a large elastic recovery and significant amorphization remains. It is remarkable that dislocation density increases during unloading, unlike what happens for most materials, where there are large reductions due to dislocation reactions and surface sinks. This “anomalous” behavior is likely associated with low dislocation mobility in diamond, but also with a large number of junctions, which increases with dislocation density and reduces even further dislocation mobility. The unloaded state includes a dense dislocation network that withstands high-temperature annealing. Analysis of the vibrational density of states (VDOS) during recovery is consistent with significant recovery of the crystalline diamond phase. Reloading of the nanoparticles shows lower strength, without significant dislocation growth.Graphical abstract[graphic not available: see fulltext]

Li, Luo; Khraishi, Tariq

doi: 10.1007/s10853-023-09174-zpmid: N/A

Simulation models are used to emulate real-world phenomena, and errors are inevitable in the numerical computation process. Owing to that, simulation models need to be verified and validated to ensure the models and their implementations are correct. In this paper, V&V has been done for the micro3d discrete dislocation dynamics (DDD) model by comparing simulation results with corresponding theory, including any analytical solutions, other numerical solutions and experimental data. DDD simulations are a powerful simulation methodology that can help researchers better understand the plastic behavior of crystalline materials. In this study, parametric analyses for DDD simulations parameters have been performed. In addition, simulation results are verified and validated.

Abou Ali Modad, Ossama; Shehadeh, Mutasem A.

doi: 10.1007/s10853-023-09084-0pmid: N/A

Martensitic steels are widely used as a structural material in critical components of fossil fuel and nuclear power plants, such as boilers, pipes, and fittings. Martensitic steels are known to have a hierarchical microstructure that follows the Kurdjumov–Sachs (K–S) orientation relationship, where a prior austenite grain is composed of packets separated by high angle grain boundaries or packet boundaries, which are, in turn, divided into blocks or variants segregated by high angle grain boundaries called block boundaries. Blocks themselves are an agglomeration of laths divided by low angle grain boundaries named lath boundaries which have precipitates scattered on them. This work seeks to examine, using a couple dislocation dynamics—continuum mechanics approach called multiscale dislocation dynamics plasticity (MDDP), the interactions between dislocations and packet, block, lath boundaries, and precipitates under uniaxial tension loading and their effect on the mechanical response of the material. The simulations are conducted at a strain rate of 105 s−1 at room temperature. The main crystallographic features that arise during the deformation process were extracted and analyzed in terms of their contribution to the mechanical response of the material. The orientation relationship governing the microstructure of martensitic steels, namely, the K–S orientation relationship, was incorporated in MDDP in an effort to accurately capture the deformation behavior of the material in question. The strength of lath martensitic steel was analyzed as a function of the lath width, block size, and packet size to determine the appropriate effective grain size.

Zafar, Hassaan; Khan, Shafique M. A.; Abu-Dheir, Numan

doi: 10.1007/s10853-023-09046-6pmid: N/A

Dislocation structure evolution during nano-indentation is investigated using a three-dimensional multi-scale discrete dislocation plasticity model. This model combines two length scales, discrete dislocation dynamics and continuum finite element analysis. The multiplication, growth and movement of dislocations on different slip planes in the vicinity of the nano-indentation site is studied. Moreover, topographical maps of the nano-indented surface are generated to observe the patterns formed by exiting dislocations. Different initial configurations of dislocation sources are employed in the study. It is observed that the dislocation activity in general and cross-slip activity in particular significantly depends upon the initial configuration of the dislocation sources. Secondly, the orientation of the crystal influences the topography of the nano-indented surface.

Marshall, Andrew; Generale, Adam; Kalidindi, Surya R.; Radhakrishnan, Bala; Belak, Jim

doi: 10.1007/s10853-024-09345-6pmid: N/A

Additive manufacturing is increasingly being employed to produce components of complex geometries in structural alloys because of the expected energy savings associated with the near-net-shape capability and the ability to build in novel internal features that are not possible with many conventional manufacturing approaches. However, because of the extreme thermal conditions encountered, the non-equilibrium microstructures produced during powder bed-based additive manufacturing processes must be subjected to custom post-heat treatment processes to recover the target mechanical properties. Phase-field models and simulation techniques have matured to a state where the microstructure evolution paths, and the morphologies of the resulting precipitate phases can be predicted reasonably accurately, considering alloy-specific thermodynamic and kinetic aspects of the nucleation and growth processes. However, phase-field simulations are computationally intensive, which precludes the ability to apply the simulations directly to the length scale of the entire component. Therefore, it is highly desirable to develop low-computational-cost surrogate models that effectively capture the physics at the microstructural length scale, while facilitating the design of optimized processing conditions resulting in location-specific targeted microstructures at the component scale. The work presented here demonstrates the application of the materials knowledge system framework to develop a surrogate model that effectively captures the microstructural path during annealing of a Ni–Mo–Nb alloy containing different Mo and Nb compositions known to segregate during solidification under additive manufacturing conditions. Specifically, the surrogate model built in this work is based on a Gaussian process autoregressive model informed by statistical representation of simulated microstructures using two-point correlations and dimensionality reduction through principal component analysis. This surrogate model is shown to capture the bifurcation of the microstructural path during precipitation, which yields a microstructure dominated by the γ′′\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${\gamma }^{{\prime}{\prime}}$$\end{document} phase at high Nb concentrations and the δ\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\delta$$\end{document} phase at low Nb concentrations.