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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 /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Mechanical Properties of Crystal-Amorphous Composites as a Function of Mean Grain Size and Grain Boundary Thickness // Zhibin Xu.
作者:	Xu, Zhibin,
面頁冊數:	1 electronic resource (81 pages)
附註:	Source: Dissertations Abstracts International, Volume: 86-06, Section: B.
Contained By:	Dissertations Abstracts International86-06B.
標題:	Mechanical properties. -
電子資源:	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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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.
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