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Mechanical Properties of Crystal-Amo...

Xu, Zhibin,

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Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness // Zhibin Xu.
Author:	Xu, Zhibin,
Description:	1 electronic resource (81 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
Contained By:	Dissertations Abstracts International86-06B.
Subject:	Mechanical properties. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31810332
ISBN:	9798346824596

Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness /
Xu, Zhibin,

Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness /Zhibin Xu. - 1 electronic resource (81 pages)

Source: Dissertations Abstracts International, Volume: 86-06, Section: B.

Mechanical properties of polycrystals have been intensively studied as a function of mean grain diameter D, but rarely as a function of (D.I) where I is the mean grain-boundary thickness. Here we measure the mechanical properties in the (D.I) space by simulation for polycrystals with thick grain boundaries which are often called as crystalline-amorphous composites. The strength σyof a polycrystal increases with Dat D≥ 50 atoms (i.e., the famous Hall-Petch (HP) behavior) and decreases at D≤ 50 (i.e., the inverse Hall-Petch (IHP) behavior). These behaviors generally hold for all kinds of polycrystals and have not been generalized to a function of other structural parameters before. Our simulations gen- eralize the HP and IHP behaviors of σy, (D) to σy, (D.1). We demonstrate that increasing I and decreasing D have similar effects on reducing dislocation motions and promoting GB deformations. Consequently, the classical HPand IHP behaviors and our generalized HP-IHP behaviors share similar mechanisms and can be unified as σy,(AtotGB/Atot), where AGB/At is the fraction of the amorphous region. In 2D, we only observe the IHP behav-ior because dislocations are rare in 2D. In 3D, we observed the HP and IHP behaviors in systems with various particle compositions and interactions. The maximum strength is ro- bustly reached at (D,I)≃ (50, 5) particles for single-component face-centered cubic solids and at (D,I) ≃(50, 2) for bidispersed or body-centered cubic solids due to their differ- ent activation stresses for dislocation motions. The deformation mechanism changes from dislocation-dominated to grain-boundary-dominated as / increases. The results explain the recent alloy experiments and provide a route to exceed the maximum strength of polycrys- tals. Besides ay, the ductility and elastic moduli are similarly measured in the broad (D.I) space. The ductile and brittle regimes in the (D.I) space exhibit distinct fracture morpholo- gies. Properly thickening grain boundaries can avoid the strength-ductility trade-off. These novel results in the (D.I) space can guide the fabrication of crystalline-amorphous compos- ites with outstanding mechanical properties.

English

ISBN: 9798346824596Subjects--Topical Terms:

3549505
Mechanical properties.

Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness /
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245 1 0 $a Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness / $c Zhibin Xu.
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300 $a 1 electronic resource (81 pages)
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500 $a Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
500 $a Advisors: Han, Yilong; Sun, Qingping.
502 $b Ph.D. $c Hong Kong University of Science and Technology (Hong Kong) $d 2024.
520 $a Mechanical properties of polycrystals have been intensively studied as a function of mean grain diameter D, but rarely as a function of (D.I) where I is the mean grain-boundary thickness. Here we measure the mechanical properties in the (D.I) space by simulation for polycrystals with thick grain boundaries which are often called as crystalline-amorphous composites. The strength σyof a polycrystal increases with Dat D≥ 50 atoms (i.e., the famous Hall-Petch (HP) behavior) and decreases at D≤ 50 (i.e., the inverse Hall-Petch (IHP) behavior). These behaviors generally hold for all kinds of polycrystals and have not been generalized to a function of other structural parameters before. Our simulations gen- eralize the HP and IHP behaviors of σy, (D) to σy, (D.1). We demonstrate that increasing I and decreasing D have similar effects on reducing dislocation motions and promoting GB deformations. Consequently, the classical HPand IHP behaviors and our generalized HP-IHP behaviors share similar mechanisms and can be unified as σy,(AtotGB/Atot), where AGB/At is the fraction of the amorphous region. In 2D, we only observe the IHP behav-ior because dislocations are rare in 2D. In 3D, we observed the HP and IHP behaviors in systems with various particle compositions and interactions. The maximum strength is ro- bustly reached at (D,I)≃ (50, 5) particles for single-component face-centered cubic solids and at (D,I) ≃(50, 2) for bidispersed or body-centered cubic solids due to their differ- ent activation stresses for dislocation motions. The deformation mechanism changes from dislocation-dominated to grain-boundary-dominated as / increases. The results explain the recent alloy experiments and provide a route to exceed the maximum strength of polycrys- tals. Besides ay, the ductility and elastic moduli are similarly measured in the broad (D.I) space. The ductile and brittle regimes in the (D.I) space exhibit distinct fracture morpholo- gies. Properly thickening grain boundaries can avoid the strength-ductility trade-off. These novel results in the (D.I) space can guide the fabrication of crystalline-amorphous compos- ites with outstanding mechanical properties.
546 $a English
590 $a School code: 1223
650 4 $a Mechanical properties. $3 3549505
650 4 $a Single crystals. $3 3681642
650 4 $a Grain boundaries. $3 748639
650 4 $a Ductility. $3 3681454
650 4 $a Yield stress. $3 3561163
650 4 $a Glass. $3 550838
650 4 $a Stress-strain curves. $3 3560389
650 4 $a Point defects. $3 874426
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650 4 $a Deformation. $2 lcstt $3 3267001
650 4 $a Alloys. $3 654175
650 4 $a Boundary conditions. $3 3560411
650 4 $a Shear strain. $3 3681605
650 4 $a Atoms & subatomic particles. $3 3560412
650 4 $a Materials science. $3 543314
690 $a 0794
710 2 $a Hong Kong University of Science and Technology (Hong Kong). $e degree granting institution. $3 3814653
720 1 $a Han, Yilong $e degree supervisor.
720 1 $a Sun, Qingping $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-06B.
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791 $a Ph.D.
792 $a 2024
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31810332