The effect of alloying elements on grain boundary and bulk cohesion in aluminum alloys: An ab initio study

Razumovskiy, Vsevolod I.; Ruban, Andrei V.; Razumovskiǐ, I. M.; Lozovoi, A.Y.; Butrim, V. N.; Vekilov, Yu. Kh.

doi:10.1016/j.scriptamat.2011.08.014

“…These metals exhibit a drastic loss of ductility in the presence of certain liquid-metals, such as gallium (Ga), bismuth (Bi), and mercury (Hg) [1][2][3][4][5][6][7][8][9][10]. Understanding the mechanisms behind LME has been of particular interest in both experimental [2,3,5,8,[10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and simulation [7,9,[26][27][28][29][30][31][32][33] research.…”

Section: Introductionmentioning

confidence: 99%

“…One of the most widely accepted LME mechanisms suggests that penetration of the liquid metal into grain boundaries (GBs) modifies interfacial energy so as to promote intergranular failure [3,9,10,20,[22][23][24]29,34,35]. Consequently, the reasons for such variation is likely associated with the specific type of liquid environments [10,18,29] tested, whereby some elements act to enhance cohesion in certain systems, while others promote decohesion [28,35]. However, recent nanoscale experimental studies suggest that one of the primary contributing factors in LME is the formation of intermetallic compounds at GBs [1] and bilayer interfacial phases (e.g., in Ni-Bi) [17].…”

Section: Introductionmentioning

confidence: 99%

Atomic-scale analysis of liquid-gallium embrittlement of aluminum grain boundaries

Rajagopalan

¹

,

Bhatia

²

,

Tschopp

³

et al. 2014

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Material strengthening and embrittlement are controlled by intrinsic interactions between defects, such as grain boundaries (GB), and impurity atoms that alter the observed deformation and failure mechanisms in metals. In this work, we explore the role of atomistic-scale energetics on liquid-metal embrittlement of aluminum (Al) due to gallium (Ga). Ab initio and molecular mechanics were employed to probe the formation/binding energies of vacancies and segregation energies of Ga for <100>, <110> and <111> symmetric tilt grain boundaries (STGBs) in Al. We found that the GB local arrangements and resulting structural units have a significant influence on the magnitude of vacancy binding energies. For example, the mean vacancy binding energy for <100>, <110>, and <111> STGBs at 1 st layer was found to be -0.63 eV, -0.26 eV, and -0.60 eV. However, some GBs exhibited vacancy binding energies closer to bulk values, indicating interfaces with zero sink strength, i.e., these GBs may not provide effective pathways for vacancy diffusion. The results from the present work showed that the GB structure and the associated free volume also play significant roles in Ga segregation and the subsequent embrittlement of Al. The Ga mean segregation energy for <100>, <110> and <111> STGBs at 1 st layer was found to be -0.23 eV, -0.12 eV and -0.24 eV, respectively, suggesting a stronger correlation between the GB structural unit, its free volume, and segregation behavior. Furthermore, as the GB free volume increased, the difference in segregation energies between the 1 st layer and the 0 th layer increased. Thus, the GB character and free volume provide an important key to understanding the degree of anisotropy in various systems. The overall characteristic Ga absorption length scale was found to be about ~10, 8, and 12 layers for <100>, <110>, and <111> STGBs, respectively. Also, a few GBs of different tilt axes with relatively high segregation energies (between 0 and -0.1 eV) at the boundary were also found. This finding provides a new atomistic perspective to the GB engineering of materials with smart GB networks to mitigate or control LME and more general embrittlement phenomena in alloys.

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“…As a typical HAGB in Al, symmetrical tilt R5 (012) [100] GB has been extensively studied by experimental [95,96] and theoretical [97,98] investigations. Hence, it was selected to represent the general HAGBs in the present study.…”

Section: B Mechanisms Underlying Stress-induced Grain Growth During mentioning

confidence: 99%

Stress-Induced Grain Growth in an Ultra-Fine Grained Al Alloy

Lin

¹

,

Wen

²

,

Liu

³

et al. 2014

Metall Mater Trans B

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This paper reports on a study of the stress-induced grain growth phenomenon in the presence of second-phase particles and solutes segregated at grain boundaries (GBs) during high-temperature deformation of an ultra-fine grained (UFG) Al alloy synthesized via the consolidation of mechanically milled powders. Our results show that grain growth was essentially inhibited during annealing at 673 K (400°C) in the absence of an externally applied stress, whereas in contrast, grain growth was enhanced by a factor of approximately 2.7 during extrusion at 673 K (400°C). These results suggest that significant grain growth during hot extrusion was attributable to the externally applied stresses stemming from the state of stress imposed during extrusion and that the externally applied stresses can overcome the resistance forces generated by second-phase particles and solutes segregated at GBs. The mechanisms underlying stress-induced grain growth were identified as GB migration and grain rotation, which were accompanied by dynamic recovery and possible geometric dynamic recrystallization, while discontinuous dynamic recrystallization did not appear to be operative. he earned his B.S. with honors in solid mechanics from Brown University. His research interests include the synthesis and behavior of nanostructured and multi-scale materials with particular emphasis on processing fundamentals and physical behavior; thermal spray processing of nanostructured materials; spray atomization and deposition of structural materials; high temperature-high pressure atomization processes; mathematical modeling of advanced materials and processes; and additive manufacturing. He has published 515 journal and 225 conference publications on topics ranging from nanomaterials to extremely strong aluminum alloys. Prof. Lavernia has delivered more than 150 invited lectures and seminars in over 17 countries. He

show abstract

“…As a typical HAGB in Al, symmetrical tilt R5 (012) [100] GB has been extensively studied by experimental [95,96] and theoretical [97,98] investigations. Hence, it was selected to represent the general HAGBs in the…”

Section: Appendixmentioning

confidence: 99%

Stress-Induced Grain Growth in an Ultra-Fine Grained Al Alloy

Lin

¹

,

Wen

²

,

Liu

³

et al. 2014

Metall Mater Trans A

View full text Add to dashboard Cite

This paper reports on a study of the stress-induced grain growth phenomenon in the presence of second-phase particles and solutes segregated at grain boundaries (GBs) during high-temperature deformation of an ultra-fine grained (UFG) Al alloy synthesized via the consolidation of mechanically milled powders. Our results show that grain growth was essentially inhibited during annealing at 673 K (400°C) in the absence of an externally applied stress, whereas in contrast, grain growth was enhanced by a factor of approximately 2.7 during extrusion at 673 K (400°C). These results suggest that significant grain growth during hot extrusion was attributable to the externally applied stresses stemming from the state of stress imposed during extrusion and that the externally applied stresses can overcome the resistance forces generated by second-phase particles and solutes segregated at GBs. The mechanisms underlying stress-induced grain growth were identified as GB migration and grain rotation, which were accompanied by dynamic recovery and possible geometric dynamic recrystallization, while discontinuous dynamic recrystallization did not appear to be operative. he earned his B.S. with honors in solid mechanics from Brown University. His research interests include the synthesis and behavior of nanostructured and multi-scale materials with particular emphasis on processing fundamentals and physical behavior; thermal spray processing of nanostructured materials; spray atomization and deposition of structural materials; high temperature-high pressure atomization processes; mathematical modeling of advanced materials and processes; and additive manufacturing. He has published 515 journal and 225 conference publications on topics ranging from nanomaterials to extremely strong aluminum alloys. Prof. Lavernia has delivered more than 150 invited lectures and seminars in over 17 countries. He

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The effect of alloying elements on grain boundary and bulk cohesion in aluminum alloys: An ab initio study

Cited by 64 publications

References 20 publications

Atomic-scale analysis of liquid-gallium embrittlement of aluminum grain boundaries

Atomic-scale analysis of liquid-gallium embrittlement of aluminum grain boundaries

Stress-Induced Grain Growth in an Ultra-Fine Grained Al Alloy

Stress-Induced Grain Growth in an Ultra-Fine Grained Al Alloy

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