Thông tin tài liệu
Computational Materials Science 188 (2021) 110130 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci Effects of magnesium dopants on grain boundary migration in aluminum-magnesium alloys Amirreza Kazemi , Shengfeng Yang * Department of Mechanical and Energy Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA A R T I C L E I N F O A B S T R A C T Keywords: Aluminum alloys Magnesium dopants Molecular dynamics Grain boundary segregation Grain boundary migration Grain boundary sliding Atomistic simulations have been used to study the grain boundary (GB) migration in pure Al and Mg-doped Al binary alloys The results of shearing simulations indicate that the effect of dopants on the GB migration depends ∑ on the character of the GB Negligible influence is found on the migration of the coherent GB and only a slight change was found in its strength due to the doping For the other GBs considered in our study, GB migration was pinned by dopants at the GBs, which results in a strengthening effect The atomic-level GB migration mechanisms are identified for both shear-coupled GB migration in pure Al and dopants pinning GB migration in Mg-doped Al alloys Introduction Nanocrystalline (NC) materials have great potential in various ap plications due to their extraordinary material properties such as high ultimate strength [1,2] However, their usage has been greatly limited by low thermal stability [3], which is caused by migrations of highenergy grain boundaries (GBs) during deformation or aging at elevated temperatures [4] The migration of GBs under mechanical loading may cause shear of the bulk region that was traversed by the GBs, which is called shear-coupled migration of GBs [5–9] The coupling factor is used to quantify the shear produced by the GB during its motion and is determined by the ratio of grain translation to GB displacement Various geometrical models [5,10,11] have been developed to predict the coupling factor Moreover, studies [5,12,13] show that the shearcoupled GB migration is temperate dependent and will transit to GB sliding with the increasing temperature A recent study [14] suggests that GB shear coupling strongly depends on temperature and the driving force for migration, and thus is not an intrinsic GB property Various atomic-level mechanisms have been proposed to explain the shear-coupled GB migration Cahn et al [5] suggested that the trans formation between GB unit and lattice structural unit leads to shearcoupled GB migration in FCC metals Ulomek et al [15] show that shuffling and its initiation are the primary atomic mechanisms for shearcoupled GB migration Recently, Zhu et al [16] used in situ shear testing to find that shear-coupled GB migration in Au bicrystals can be formed by the motion of GB disconnections Both single-layer and double-layer disconnections contribute to GB migration through their composition and decomposition Moreover, they found that the disconnectionmediated GB migration is reversible in cyclic shear loading However, all the aforementioned mechanisms were proposed for pure materials and did not consider the effect of dopants As the dopants will greatly influence the mobility of GBs due to the change of structure and chemistry of GBs [17–21], it is not clear that these mechanisms will be still valid for alloys with dopants In this study, atomistic simulations are used to study the effect of Mg dopants on GB migration in Al alloys Mg is one of the most important alloying elements for Al, and Mg-rich 5xxx Al alloys are widely used as lightweight and high-strength materials The addition of Mg dopants can help to improve the mechanical properties of Al alloy through various mechanisms, such as solid solution strengthening [22,23], precipitates pinning GBs [24,25], and GB segregation strengthening [2] A recent experimental study [4] shows that alloying Al with Mg dopants is an effective way to increase their thermal stability A prior study of Mgdoped polycrystalline Al [26] suggested that Mg dopants tend to segregate to GBs and help to prohibit the migration of GBs However, general GBs were used in this study without specific GB characters, thus the effect of GB character on GB migration is not clear By directly putting Mg dopants at GBs in the simulation models, Babicheva et al [27] found that the deformation mechanism for the NC Al-Mg alloy and Al-Mg bi-crystals with different misorientations is GB sliding with no contribution from GB migration Rahman et al [28] observed a strong solute pinning effect at all misorientations for different GBs in Mg-doped * Corresponding author E-mail address: yangsf@iupui.edu (S Yang) https://doi.org/10.1016/j.commatsci.2020.110130 Received 17 January 2020; Received in revised form October 2020; Accepted 10 October 2020 Available online November 2020 0927-0256/© 2020 Elsevier B.V All rights reserved A Kazemi and S Yang Computational Materials Science 188 (2021) 110130 Al These prior studies indicate that the character of the GB doesn’t change the migration mechanism of GBs However, our research results in this work show that the GB migration mechanism strongly depends on the character of the GB The objective of our study is to investigate the effect of GB character on the atomic-level GB migration mechanisms in Al using atomistic simulations [001]/(210) are shown in Fig Based on CNA, the Al atoms in FCC bulk lattice are colored in green and the Al atoms with other structures, e.g at GBs, are colored in white To show the distribution of Mg dopants clearly, they are colored in blue The results in Fig clearly show that ∑ ∑ more Mg dopants are segregated to the 5[001]/(210) GB than the [110]/(111) GB We calculated the dopant concentration at GB with the same approach used by Rahman et al [24] Briefly, the computational cell is divided into several bins in the direction normal to the GB The average dopant concentration for each bin is plotted against the distance to the GB and the peak at the center of the plot is the dopant concen tration at the GB region The determined GB dopant concentration for ∑ ∑ the 3[110]/(111) GB and the 5[001]/(210) GB are 5.6% and ∑ 12.6%, respectively Mg dopants are segregated to the 5[001]/(210) GB in a regular pattern, in which the dopants locate in the center layer of the GB structural units This segregation behavior is similar in the other five GBs We calculated the GB energy using γ GB = (EGB-Nµ)/2A, where EGB is the total energies of the computational cell with GBs; A is the GB area; N is the numbers of Al atoms contained in the cell; µ is the cohesive energy per Al atom, which is calculated from the bulk fcc Al The scaling factor of ½ is because we have two GBs in the cell due to the periodic boundary ∑ condition The determined GB energies for the 3[110]/(111) GB and ∑ the 5[001]/(210) GB are 0.0506 J/m and 0.3103 J/m2, respectively ∑ ∑ Compared to the 5[001]/(210) GB, the 3[110]/(111) GB has a much lower GB energy, which is consistent with the literature results [36] obtained from first-principles calculations Compared to the Σ5 [001]/(210) GB, the Σ3[110]/(111) GB has a much lower GB energy, which results in a distinct segregation behavior of dopants at GBs Moreover, the size mismatch between Al and Mg atoms also contribute to the different behavior of different GBs As the relative metallic radius (RMg/RAl) is 1.23, more large-sized Mg atoms tend to segregate to GBs with more free volume Therefore, a larger dopant concentration is ∑ observed in the 5[001]/(210), which has more free volume at the GB ∑ core and a less compact GB structure than the 3[110]/(111) GB The experimental research by Pun et al [2] has observed that Mg tends to segregate at Al GBs in Al-7%Mg Liu et al [37] used the Monte-Carlo (MC) method to find that the segregation of Mg dopants varies with the misorientation angle of the GB in Al-10%Mg However, due to the limitation of the MC method, no atomic structures of GB with dopants were provided Our simulation in this work directly shows the atomic structure of the dopants-segregated GBs, which provides clearer evi dence that the GB segregation of Mg dopants at Al GBs depends on the GB character As shown in Fig 2a, the shear strain was applied in the direction parallel to the GB plane during the shearing tests, and the system was free to expand or shrink in the other two directions A constant strain rate of 109 s− was used The stress–strain curves for both pure Al and Al∑ Mg alloy are plotted in Fig 2b The results indicate that the 3[110]/ ∑ (111) GB has a larger yield strength and flow stress than the 5[001]/ (210) GB The Young’s modulus decreases with the addition of Mg dopants as Mg has a smaller modulus than Al Moreover, the addition of ∑ Mg dopants leads to an increase of yield strength for the 5[001]/(210) ∑ GB but not for the 3[110]/(111) GB The strengthening effect of Mg dopants has been overserved by Pun et al [2] and Lee et al [22] Our simulation results show that the strengthening effect also depends on the GB character, which is caused by different segregation behavior in different GBs To identify the atomic-level mechanisms for the strengthening effect of Mg dopants on Al bicrystals, we tracked the motion of GBs during the ∑ shearing simulations The normal displacement of the 3[110]/(111) GB is not affected by Mg dopants (Fig 3a), while the displacement of the ∑ 5[001]/(210) GB is greatly decreased by adding Mg dopants For the ∑ 3[110]/(111) GB, the shear-coupled GB migration occurs to accom modate the shear strain in both pure Al and Mg-doped Al However, for ∑ other GBs like 5[001]/(210), the shear-coupled GB migration occurs in pure Al (Fig 3b-d), but no GB migration is observed to accommodate Computational details ∑ Bicrystal Al models were created for seven different tilt GBs, ∑ ∑ ∑ ∑ [110]/(111), 5[100]/(210), 5[100]/(310), 9[110]/(212), 13 ∑ ∑ [100]/(230), 13[100]/(510), and 29[100]/(520) To generate a tilt grain boundary, two separate crystals were first constructed by rotating the crystal around the same crystallographic tilt axis The rotation angles for these two crystals have different directions but have the magnitude of a half of the disorientation angle for the GB These two crystals are cut by the GB plane and then stacked to create a periodic GB structure If any two atoms at the GB are too close to each other based on a distance torlerance of 0.5 Å, one of the two atoms will be deleted The dimensions of the simulation cell were set to around 35 Å, 180 Å, and 340 Å along the ×, y, and z directions, respectively The bicrystal models contained about 125,000 atoms Periodic boundary conditions were applied in all directions and thus there are two identical grain boundaries in each bicrystal model A Finnis-Sinclair (F-S) type of interatomic potential [29] was used to describe the interatomic interactions as it well re produces the thermal and mechanical properties of Al-Mg alloys [30,31] The solidus and liquidus lines at the Al-rich side of the phase diagram are well reproduced by this potential [29] Hybrid Monte Carlo/molecular dynamics (MC/MD) simulations are used to introduce Mg dopants into Al bicrystals in order to obtain an equilibrium distribution of Mg dopants Hybrid MC/MD [32,33] is an effective method to make dopants to achieve an equilibrium distribution in simulation systems During MC/MD simulations, MD steps are used to relax the atomic structure, while MC steps to sample the semi-grand canonical ensemble The probability of swapping Al atoms with Mg atoms is dictated by the Metropolis criterion at the set temperatures When the magnitude of energy fluctuation over 10,000 steps is less than 0.5%, the simulation is considered to reach an equilibrium The chem ical potential difference between Mg and Al will influence the dopant concentration in the model Therefore, we tested a number of different values for the chemical potential difference The chemical potential difference of 1.9 eV was chosen to achieve the desired 3.5% Mg dopants into the models Both chemical and mechanical equilibrium was ach ieved in MC/MD simulations at the temperature of 300 K and zero pressure Mechanical equilibrium is achieved through MD steps using NPT ensemble The chemical equilibrium is achieved by using a semigrand canonical ensemble to obtain an equilibrium distribution of the Mg solutes in both the bulk phases and GBs in the binary Al-Mg alloy system During the shearing tests, the shear loading was applied by tilting the computational cell in the y-direction as shown in Fig Shear strain is defined as offset/length, where the length is the cell length perpendic ular to the shear direction and the offset is the displacement distance in the shear direction from the unstrained orientation NPT ensemble was used during the shearing loading The temperature was set to 300 K and zero pressure was applied The time step was set to 0.1 fs A constant strain rate of 109 s− was applied LAMMPS [34] was used to perform all the simulations, and OVITO [35] was used to visualize the atomic structures Results and discussion The atomic structures of GBs for Al-3.5at.%Mg were obtained after fully relaxation using MC/MD simulations Out of the seven different ∑ GBs, we find that the GB segregation of the 3[110]/(111) is different ∑ ∑ from the other six GBs The atomic structures of this GB and a A Kazemi and S Yang Computational Materials Science 188 (2021) 110130 ∑ ∑ Fig Fully relaxed bicrystal models of Al-3.5at.%Mg alloy and zoom-in grain boundary structure: (a) 3[110]/(111) tilt GB and (b) 5[001]/(210) tilt GB The Al atoms with fcc structure are colored green; the Al atoms with structures other than fcc are colored white; and the blue atoms are Mg atoms Fig Shearing simulations of pure Al and Al-Mg alloy: (a) computational model and loading for shearing simulations; (b) Stress–strain curves obtained from ∑ ∑ shearing simulations of pure Al and Al-3.5%Mg alloy for 3[110]/(111) tilt GB and 5[001]/(210)tilt GB the shearing deformation in Mg-doped Al GBs (Fig 3e-g) Moreover, it ∑ should be noted that the width of the 5[001]/(210) GB in Mg-doped Al increases with the increasing shear strain The GB width increases from nm (strain = 0.0) to 2.4 nm (strain = 0.2) If the same GB region with the same width of nm is used to calculate the GB dopant con centration, the GB dopant concentration increases from 12.6% (strain = 0.0) to 15.9% (strain = 0.2) Therefore, the increase of the GB width leads to stronger segregation of dopants to the GB core ∑ The atomic mechanisms of shear-coupled GB migration in the ∑ [110]/(111) GB and the 5[001]/(210) GB for pure Al are shown in Fig A GB disconnection [16] was first formed by applied shear stress and then propagated along the GB The transformation of 4-member lattice structural unit A to the 4-member GB unit B leads to the propa ∑ gation of the GB disconnection in the 3[110]/(111) GB (Fig 4a) As the GB disconnection travel through the entire GB, the GB will migrate in the normal direction by one elementary step and a tangential trans lation will happen between the two grains due to the shear-coupling effect This finding agrees with the mechanism observed by Cahn ∑ ∑ et al [5] for a 17 (5 0) GB in Cu Similarly, for the 5[001]/(210) GB (Fig 4b), the conversion between the six-member lattice structural unit C to the six-member GB unit D drives the GB disconnection to move through the entire GB In Fig 3, a step-wise increase in the GB A Kazemi and S Yang Computational Materials Science 188 (2021) 110130 ∑ ∑ Fig GB displacement–strain curves obtained from shearing simulations of pure Al and Al-3.5%Mg alloy for 3[110]/(111) tilt GB and 5[001]/(210) tilt GB ∑ The associated atomic structures of the 5[001]/(210) GB for pure Al (b) – (d) and Al-Mg alloy (e)-(g) are plotted at the applied strains of 0.0, 0.1, and 0.2, respectively ∑ ∑ Fig Atomic mechanisms of shear-coupled GB migration of the (a) 3[110]/(111) tilt GB and (b) 5[001]/(210) tilt GB for pure Al The GB migration is caused ∑ ∑ by the conversion of structural unit A to B in 3[110]/(111) GB and the conversion of unit C to D in 5[001]/(210) GB The Al atoms with fcc structure are colored green; the Al atoms with hcp structures are colored red; the Al atoms with structures other than fcc and hcp are colored white ∑ displacement was observed for the 3[110]/(111) GB while a linear ∑ increase was observed for the 5[001]/(210) GB This is because the ∑ GB migration in the 3[110]/(111) GB is not continuous As the ∑ structural units A and B at the 3[110]/(111) GB only contain four atoms, the conversion between A and B is easier compared to the six∑ member structural units in the 5[001]/(210) GB Therefore, the ∑ conversion of structural units is propagated much faster through the [110]/(111) GB and thus the GB migration tends to occur in a short period of time The GB migration stops until the occurrence of the next migration This results in the step-wise increase in the GB displacement ∑ for 3[110]/(111) GB The effect of dopants on the GB migration depends on the character ∑ of the GB For the GB like 3[110]/(111), the dopants tend to randomly distribute in the bulk and the GB, and no strong GB segregation of dopants is observed In this case, dopants only have a negligible influ ence on the migration of GB, as shown in Fig 3a As a result, only a slight change was found in the strength of the twin GB, as shown in Fig 2b For other GBs in our study, we find strong segregation of Mg dopants at GBs, and GB migration was pinned by dopants at the GBs The pinning effect of dopants on GB migration was also found in an earlier study by Rah man et al [38], in which artificial driving force (ADF) techniques were used to induce GB motions This pinning effect of Mg dopant on GB migration is related to both the charge density depletion and volumetric expansion at GBs induced by Mg segregation Both of them will lead to weakend bonds at the GBs DFT calculation [39] shows that Mg dopants decrease the bonding charge density of Al atoms at the GB Moreover, as the atomic size of Mg is larger than Al, the atomic bonds connecting two grains across the GB will be elongated and thus the bond strength near the GB will be weakened Therefore, the weakened bonds at GB will prevent the nucleation and conversion of the structural units at GB and thus pin GB migration This dopants pinning effect on GB migration leads to a strengthening effect on the yield strength and flow stress of Al Fig shows the stress–strain curve and the associated GB structures ∑ for the 13[001]/(230) tilt GB It is found that the GB structure transformed into ring-like structures when subjected to a small shear strain of ~0.01 The ring-like structures (Fig 5b) have a smaller atomic density than the initial GB structure (Fig 5a) It should be noted that the majority of the dopants locate in the centers of the rings at the GB As shown in a recent DFT study [39], the Al-Al distance at the GB will in crease due to the doping of Mg at the Al GB The formed ring-like structures are stable until the material yields at the applied strain of ~0.06 We tracked the movement of two slabs of atoms, colored in red in Fig 5, to track the GB sliding between the two grains As shown in Fig 5c, no significant GB sliding occurred before yielding After the material yields, amorphous layers formed around the ring-like GB structure units, and the GB sliding started to operate between the two grains through the amorphous layers (Fig 5d) The study of the other five GBs shows that the formation of ring-like structures is typical, as shown in Fig All the GBs developed ring-like GB structure units when subjected to a small shear strain and kept similar structures until the A Kazemi and S Yang Computational Materials Science 188 (2021) 110130 Fig Stress–strain curve and the associated GB structures for shearing simulations of pure Al and Al-3.5at.%Mg alloy for the atoms are highlighted in red to track the translation between the two grains ∑ 13[001]/(230) tilt GB Two slabs of Fig Formation of typical ring-like structures with dopants at their centers for different GBs at the applied shear strain of 0.05 for Al-3.5at.%Mg alloy material yields This finding significantly enriches our fundamental understanding of the process of dopants pinning GB motion in metallic materials Our study illustrates that Mg dopants can be used to effectively suppress the GB migration in nanocrystalline Al and thus stabilize its grain size during the deformation Recent experiments [24] also show that the grain size of Al-Mg alloys was much smaller compared to pure Al even though they received the same thermal treatments The results indicate that GB doping is a useful way to achieve stable nanocrystalline materials during deformation However, our results also suggest that the effect of dopants on pinning GB migrations heavily depends on the type of GBs Therefore, the effect of GB character on GB migration should be taken into consideration during the deformation of nanocrystalline materials Conclusion Atomic mechanisms for GB deformations in pure Al GBs and Mgdoped Al GBs have been identified from our atomistic simulation re sults Shear-coupled GB migration accommodates the shear deformation during shearing simulations for pure Al bicrystals The conversion be tween lattice units and GB structural units results in the propagation of GB disconnection through the entire GB, which leads to GB migration in the normal direction by one elementary step and a coupled tangential A Kazemi and S Yang Computational Materials Science 188 (2021) 110130 translation between the two grains The effect of dopants on the GB ∑ migration depends on the character of the GB For the 3[110]/(111) GB, no strong GB segregation of dopants is observed and negligible in fluence is found on GB migration Only a slight change was found in the ∑ strength of the GB due to the doping However, for other GBs in our study, a strong GB segregation of Mg dopants is found and GB migration was pinned by dopants at the GBs, which results in a strengthening effect on Al bicrystals due to doping When GBs were subjected to a small shear strain, the GB structure transformed into ring-like structures with the dopants locating in the centers of the rings The formed ring-like structures are stable and no significant GB sliding occurred until the material yields After the material yields, amorphous layers formed around the ring-like GB structure units and the GB sliding started to operate between the two grains through the amorphous layers [9] H Zhang, D.J Srolovitz, J.F Douglas, J.A Warren, Atomic motion during the migration of general [001] tilt grain boundaries in Ni, Acta Mater 55 (13) (2007) 4527–4533 [10] E.R Homer, S.M Foiles, E.A Holm, D.L Olmsted, Phenomenology of shearcoupled grain boundary motion in symmetric tilt and general grain boundaries, Acta Mater 61 (4) (2013) 1048–1060 [11] K.D Molodov, D.A Molodov, Grain boundary mediated plasticity: On the evaluation of grain boundary migration – shear coupling, Acta Mater 153 (2018) 336–353 [12] A.-K Maier, D Mari, I Tkalcec, R Schaller, Theoretical modelling of grain boundary anelastic relaxations, Acta Mater 74 (2014) 132–140 [13] J.-E Brandenburg, D.A Molodov, On shear coupled migration of low angle grain boundaries, Scr Mater 163 (2019) 96–100 [14] K Chen, J Han, S.L Thomas, D.J Srolovitz, Grain boundary shear coupling is not a grain boundary property, Acta Mater 167 (2019) 241–247 [15] F Ulomek, V Mohles, Separating grain boundary migration mechanisms in molecular dynamics simulations, Acta Mater 103 (2016) 424–432 [16] Q Zhu, G Cao, J Wang, C Deng, J Li, Z Zhang, S.X Mao, In situ atomistic observation of disconnection-mediated grain boundary migration, Nat Commun 10 (1) (2019) 156 [17] P.R Cantwell, M Tang, S.J Dillon, J Luo, G.S Rohrer, M.P Harmer, Grain boundary complexions, Acta Mater 62 (2014) 1–48 [18] T Frolov, Y Mishin, Phases, phase equilibria, and phase rules in low-dimensional systems, J Chem Phys 143 (4) (2015), 044706 [19] W.D Kaplan, D Chatain, P Wynblatt, W.C Carter, A review of wetting versus adsorption, complexions, and related phenomena: the rosetta stone of wetting, J Mater Sci 48 (2013) 5681–5717 [20] T Hu, S.F Yang, N.X Zhou, Y.Y Zhang, J Luo, Role of disordered bipolar complexions on the sulfur embrittlement of nickel general grain boundaries, Nat Commun (2018) 2764 [21] S.F Yang, N.X Zhou, H Zheng, S.P Ong, J Luo, First-order interfacial transformations with a critical point: Breaking the symmetry at a symmetric tilt grain boundary, Phys Rev Lett 120 (8) (2018), 085702 [22] B.-H Lee, S.-H Kim, J.-H Park, H.-W Kim, J.-C Lee, Role of Mg in simultaneously improving the strength and ductility of Al–Mg alloys, Mater Sci Eng., A 657 (2016) 115–122 [23] D Olmsted, L Hectorjr, W Curtin, Molecular dynamics study of solute strengthening in Al/Mg alloys, J Mech Phys Solids 54 (8) (2006) 1763–1788 [24] W.W.A Devaraj, R Vemuri, L Kovarik, X Jiang, M Bowden, J.R Trelewicz, S Mathaudhu, A Rohatgie, Grain boundary segregation and intermetallic precipitation in coarsening resistant nanocrystalline aluminum alloys, Acta Mater 165 (2018) 698–708 [25] X Sauvage, N Enikeev, R Valiev, Y Nasedkina, M Murashkin, Atomic-scale analysis of the segregation and precipitation mechanisms in a severely deformed Al-Mg alloy, Acta Mater 72 (2014) 125–136 [26] A Kazemi, S Yang, Atomistic Study of the Effect of Magnesium Dopants on the Strength of Nanocrystalline Aluminum, JOM 71 (4) (2019) 1209–1214 [27] R.I Babicheva, S.V Dmitriev, L Bai, Y Zhang, S.W Kok, G Kang, K Zhou, Effect of grain boundary segregation on the deformation mechanisms and mechanical properties of nanocrystalline binary aluminum alloys, Comput Mater Sci 117 (2016) 445–454 [28] M.J Rahman, H.S Zurob, J.J Hoyt, Molecular dynamics study of solute pinning effects on grain boundary migration in the aluminum magnesium alloy system, Metall Mater Trans A 47 (4) (2016) 1889–1897 [29] M.I Mendelev, M Asta, M.J Rahman, J.J Hoyt, Development of interatomic potentials appropriate for simulation of solid–liquid interface properties in Al–Mg alloys, Phil Mag 89 (34–36) (2009) 3269–3285 [30] B Jelinek, J Houze, S Kim, M.F Horstemeyer, M.I Baskes, S.-G Kim, Modified embedded-atom method interatomic potentials for theMg− Al alloy system, Phys Rev B 75 (5) (2007), 054106 [31] X.-Y Liu, P.P Ohotnicky, J.B Adams, C.L Rohrer, R.W Hyland, Anisotropic surface segregation in Al Mg alloys, Surf Sci 373 (2) (1997) 357–370 [32] B Sadigh, P Erhart, A Stukowski, A Caro, E Martinez, L Zepeda-Ruiz, Scalable parallel Monte Carlo algorithm for atomistic simulations of precipitation in alloys, Phys Rev B 85 (18) (2012), 184203 [33] S Jonathan, S Alexander, A Karsten, Plastic deformation of nanocrystalline Pd–Au alloys: On the interplay of grain boundary solute segregation, fault energies and grain size, Acta Mater 59 (8) (2011) 29572968 [34] S Plimpton, Fast parallel algorithms for short-range molecular-dynamics, J Comput Phys 117 (1) (1995) 1–19 [35] A Stukowski, Visualization and analysis of atomistic simulation data with OVITOthe Open Visualization Tool, Modell Simul Mater Sci Eng 18 (1) (2010), 015012 [36] R Mahjoub, K.J Laws, N Stanford, M Ferry, General trends between solute segregation tendency and grain boundary character in aluminum – An ab inito study, Acta Mater 158 (2018) 257–268 [37] X.Y Liu, J.B Adams, Grain-boundary segregation in Al–10%Mg alloys at hot working temperatures, Acta Mater 46 (10) (1998) 3467–3476 [38] M.J Rahman, H.S Zurob, J.J Hoyt, Molecular dynamics study of solute pinning effects on grain boundary migration in the aluminum magnesium alloy system, Metall Mater Trans A-Phys Metall Mater Sci 47a(4) (2016) 1889–1897 [39] D Zhao, O.M Løvvik, K Marthinsen, Y Li, Segregation of Mg, Cu and their effects on the strength of Al Σ5 (210)[001] symmetrical tilt grain boundary, Acta Mater 145 (2018) 235–246 CRediT authorship contribution statement Amirreza Kazemi: Methodology, Investigation, Formal analysis, Data curation, Validation, Writing - review & editing Shengfeng Yang: Conceptualization, Investigation, Funding acquisition, Project adminis tration, Supervision, Writing - original draft, Writing - review & editing Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Acknowledgement This work is financially supported by the faculty start-up funding provided by Purdue School of Engineering and Technology at Indiana University Purdue University Indianapolis This research was supported in part by Lilly Endowment, Inc., through its support for the Indiana University Pervasive Technology Institute, and in part by the Indiana METACyt Initiative The Indiana METACyt Initiative at IU was also supported in part by Lilly Endowment, Inc This work used the Extreme Science and Engineering Discovery Environment (XSEDE) under award allocation number TG-MSS180015 Data availability The raw data required to reproduce these findings are available to download from http://www.multiscalesimulation.com/ The processed data required to reproduce these findings are available to download from http://www.multiscalesimulation.com/ References [1] I.A Ovid’ko, R.Z Valiev, Y.T Zhu, Review on superior strength and enhanced ductility of metallic nanomaterials, Prog Mater Sci 94 (2018) 462–540 [2] S.C Pun, W.B Wang, A Khalajhedayati, J.D Schuler, J.R Trelewicz, T.J Rupert, Nanocrystalline Al-Mg with extreme strength due to grain boundary doping, Mat Sci Eng a-Struct 696 (2017) 400–406 [3] T Chookajorn, H.A Murdoch, C.A Schuh, Design of stable nanocrystalline alloys, Science 337 (6097) (2012) 951–954 [4] W.W.A Devaraj, R Vemuri, L Kovarik, X Jiang, M Bowden, J.R Trelewicz, S Mathaudhu, A Rohatgie, Grain boundary segregation and intermetallic precipitation in coarsening resistant nanocrystalline aluminum alloys, Acta Mater 165 (2019) 698–708 [5] J.W Cahn, Y Mishin, A Suzuki, Coupling grain boundary motion to shear deformation, Acta Mater 54 (19) (2006) 4953–4975 [6] X Yang, J Li, P Wang, Grain boundary migration in nanocrystalline Ni under constant shear strains and its mechanism, Comput Mater Sci 176 (2020), 109530 [7] S.V Bobylev, N.F Morozov, I.A Ovid’ko, Cooperative grain boundary sliding and migration process in nanocrystalline solids, Phys Rev Lett 105 (5) (2010), 055504 [8] A.D Sheikh-Ali, Coupling of grain boundary sliding and migration within the range of boundary specialness, Acta Mater 58 (19) (2010) 6249–6255 ... experimental research by Pun et al [2] has observed that Mg tends to segregate at Al GBs in Al- 7 %Mg Liu et al [37] used the Monte-Carlo (MC) method to find that the segregation of Mg dopants... nanocrystalline Al and thus stabilize its grain size during the deformation Recent experiments [24] also show that the grain size of Al- Mg alloys was much smaller compared to pure Al even though... bicrystal model A Finnis-Sinclair (F-S) type of interatomic potential [29] was used to describe the interatomic interactions as it well re produces the thermal and mechanical properties of Al- Mg alloys
Ngày đăng: 15/02/2023, 12:33
Xem thêm:
