A micromechanical model for heterogeneous nanograined metals with shape effect of inclusions and geometrically necessary dislocation pileups at the domain boundary

Li, Jianjun1,2; Chen, Shaohua3; Weng, George J.4; Lu, Wenjun5

2021-09-01

10.1016/j.ijplas.2021.103024

INTERNATIONAL JOURNAL OF PLASTICITY   影响因子和分区

0749-6419

1879-2154

Heterogeneous nanostructured materials, including metals, alloys, and composites, have attracted significant scientific interest because of their outstanding performance in overcoming the strength-ductility trade-off, enhancing fatigue strength, and reducing friction and wear damage. In this study, we developed a new micromechanical model to predict the overall mechanical response of heterogeneous nanograined metals that consist of plastically deformable soft and hard domains. This dual-domain heterogeneous structure was modeled as a matrix-inclusion system, and the problem was solved through a secant-moduli approach that considered the existence of geometrically necessary dislocation (GND) pileups at the domain boundaries. We assumed that the inclusions are aligned along one direction according to experimental observations. A significant improvement in this development from previous micro-mechanical models was that the hetero-deformation induced extra strengthening inside the plastically deformable inclusions of different shapes due to the GND pileups was taken into account. In this process, the stress-strain responses of the constituent phases of various grain sizes that spanned over four orders of magnitude are also established by the dislocation density-based model. In accordance with Eshelby's equivalent-inclusion principle, the inclusions are taken to be of spheroidal shape, with an aspect ratio (i.e., length-to-diameter ratio, denoted by fi) that could be much larger or smaller than unity. We considered in details the condition that the overall uniaxial tension is applied along the direction of the aligned inclusions, and examined the consequences if the extra strengthening is not considered and if it is considered. It is found that, if extra strengthening was not considered, the inclusion shape had a significant influence on the strain-hardening capability of the heterogeneous metals. The strain-hardening rate increased with increasing fi if fi >= 1, whereas it decreased with increasing fi if fi < 1, which resulted in a maximum strain-hardening rate at fi = 100 and a minimum one at fi = 0.5 among all the aspect ratios considered. Interestingly, the strength-ductility trade-off could be overcome by modulating only the shape of the inclusions. In contrast, if extra strengthening was incorporated, the variation of the strain hardening rate was reversed because larger fi (as fi >= 1) provided less strain partitioning, lower GND density, and reduced back stress, whereas bigger fi (as fi < 1) yielded higher ones. When the overall uniaxial stress was applied normal to the direction of the aligned inclusions, the fi dependence of the strain-hardening rate was different. Our findings showed that the tuning of inclusions shape, extra strengthening, grain sizes, and volume fractions of the inclusions circumvented the strength-ductility trade-off and achieved outstanding strength-ductility synergy as demonstrated by the strength-ductility map.

Strengthening mechanisms Constitutive behavior Analytic functions Grain boundaries Extra strain hardening

SCI ; EI

英语

通讯

National Natural Science Foundation of China (NSFC)[11872380] ; Natural Science Foundation of Hunan Province["2019JJ50750","2020JJ3043"]

Engineering ; Materials Science ; Mechanics

Engineering, Mechanical ; Materials Science, Multidisciplinary ; Mechanics

WOS:000671112000001

PERGAMON-ELSEVIER SCIENCE LTD

ENGINEERING

Web of Science

1.Cent South Univ, Sch Mech & Elect Engn, Lushan South Rd 932, Changsha 410083, Hunan, Peoples R China
2.Cent South Univ, State Key Lab High Performance Complex Mfg, Changsha 410083, Hunan, Peoples R China
3.Beijing Inst Technol, Inst Adv Struct Technol, Beijing 100081, Peoples R China
4.Rutgers State Univ, Dept Mech & Aerosp Engn, New Brunswick, NJ 08903 USA
5.Southern Univ Sci & Technol, Dept Mech & Energy Engn, Shenzhen 518055, Peoples R China

Li, Jianjun,Chen, Shaohua,Weng, George J.,et al. A micromechanical model for heterogeneous nanograined metals with shape effect of inclusions and geometrically necessary dislocation pileups at the domain boundary[J]. INTERNATIONAL JOURNAL OF PLASTICITY,2021,144.

Li, Jianjun,Chen, Shaohua,Weng, George J.,&Lu, Wenjun.(2021).A micromechanical model for heterogeneous nanograined metals with shape effect of inclusions and geometrically necessary dislocation pileups at the domain boundary.INTERNATIONAL JOURNAL OF PLASTICITY,144.

Li, Jianjun,et al."A micromechanical model for heterogeneous nanograined metals with shape effect of inclusions and geometrically necessary dislocation pileups at the domain boundary".INTERNATIONAL JOURNAL OF PLASTICITY 144(2021).