Progress in Strengthening and Toughening Mechanisms of Heterogeneous Nanostructured Metals
LU Lei(), ZHAO Huaizhi
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Cite this article:
LU Lei, ZHAO Huaizhi. Progress in Strengthening and Toughening Mechanisms of Heterogeneous Nanostructured Metals. Acta Metall Sin, 2022, 58(11): 1360-1370.
Heterostructured metals typically exhibit excellent mechanical properties, such as high strength, plasticity, and fracture toughness, which are not present in conventional homogeneous materials. This is primarily due to the synergistic effects arising from the interactions between the internal components including the stress/strain gradients, geometrically necessary dislocations, and unique interfacial behavior. This study focuses on two typical heterogeneous nanostructures (laminated and nanotwinned) by reviewing the recent progress in their strengthening and toughening mechanisms. The analysis highlights the effects of the properties and sizes of the individual components, interfaces, and loading directions on the macroscopic strengthening and toughening behavior.
Fund: National Natural Science Foundation of China(51931010);National Natural Science Foundation of China(92163202);Key Research Program of Frontier Science and International Partnership Program, Chinese Academy of Sciences(GJ-HZ2029);Liaoning Revitalization Talents Program(XLYC1802026)
About author: LU Lei, professor, Tel: (024)23971939, E-mail: llu@imr.ac.cn
Fig.1 Microstructures and engineering stress-strain curves of laminated Cu/Cu4Zn and Cu/Cu32Zn, or nanotwinned Cu samples (GNT—gradient nanotwinned, HNT—homogeneous nanotwinned) (a, b) microstructures of laminated Cu/Cu4Zn (a) and Cu/Cu32Zn (b) with layer thickness (λ) of 19 μm[33] (c, d) tensile engineering stress-strain curves of freestanding Cu, Cu4Zn, and Cu32Zn samples (c), and laminated Cu/Cu4Zn, Cu/Cu32Zn with different layer thicknesses (d) (Inset in Fig.1c shows work-hardening rate vs true strain of freestanding Cu, Cu4Zn, and Cu32Zn)[33] (e-g) schematics of microstructures of three sandwiched nanotwinned Cu samples (GNT-??, GNT-??, and GNT-??) (e), and their engineering stress-strain curves (f) and work hardening rate (Θ) vs true strain curves (g) in comparison to their HNT components[34]
Fig.2 Sampling schematic diagram, cross-sectional microstructures, and stress-strain curves of DPD Cu (DPD—dynamic plastic deformation)[45] (a) schematic of the tensile specimens in the DPD disc and their orientations relative to the twin boundaries (TBs), i.e., parallel, normal, and 45° inclined to TBs, hereafter referred to as sample-P, sample-N, and sample-I, respectively (b, d) typical cross-sectional microstructures of DPD Cu, showing the nanotwins (NT) in the form of bundles embedded in a matrix of nanograins (NG) (c) tensile engineering stress-strain curves for the DPD processed heterogeneous nanostructured Cu and the coarse-grained (CG) Cu serve as a counterpart for comparison (e-g) local strain fields in sample-P (e), sample-N (f), and sample-I (g) at applied strain of 1.0%. The nanotwinned regions are denoted as NT, where the underscore indicated the direction parallel to TBs. The black dash lines indicate the position of the NT/NG interfaces. The tensile axes (TA) are represented by the double-headed arrows
Fig.3 Toughening mechanisms recorded in laminated materials with different cracking orientations relative to the heterointerfaces (a-e), EBSD and SEM images of the Al-7075/Al-1050 laminate (f-h) (a-c) crack arrester orientation with both crack plane and crack growth direction perpendicular to the interfaces, where the crack deflection, delamination, or crack bridging may be activated (d, e) crack divider orientation with the crack plane perpendicular to the interfaces while the crack growth direction parallel to the interfaces, where the delamination may be developed (f, g) EBSD maps show the microstructure of the Al-7075/Al-1050 laminate[54] (h) SEM image of a Charpy fractured sample of the Al-7075/Al-1050 laminate tested in crack arrester orientation[54]
Fig.4 Microstructure and fracture toughness of nanolayered metals[60] (a, b) microstructures and corresponding SAED patterns (insets) of Cu/Nb (a) and Cu/Zr (b) nanolayered films (c) dependence of fracture toughness (KIC) on the thickness of Cu layer (hCu) for the Cu/Nb and Cu/Zr films (dots and left y-axis), and the calculated normalized KIC (lines and right y-axis) at different normalized cohesive strengths (σc / μ, where σc is cohesive strength and μ is the shear modulus of Cu layer)
Fig.5 Schematic illustration of the CT specimens and their orientations, J-integral resistance(J-R) curves, and schematic illustrations of the failure process for the DPD Cu samples[16] (CT—compact tension) (a) schematic illustration of the CT specimens and their orientations in the DPD disc. The CT specimens were labeled with two-letter codes based on the crack plane orientation and crack growth direction with respect to the TBs inside the NTBs, i.e., parallel (P), normal (N), and 45° inclined (I) to the TBs, respectively; i.e., P-P, N-N, I-I and N-P, where the first letter designates the orientation of the expected crack plane with respect to the TBs, while the second letter designates the crack propagation direction with respect to the TBs (b) J-R curves (c-f) schematic illustration of the failure process under different cracking orientations (The insert SEM image in Fig.5e shows a micro-crack (indicated by the white arrow) initiated at the NT/NG interface)
Meyers M A, Mishra A, Benson D J. Mechanical properties of nanocrystalline materials [J]. Prog. Mater. Sci., 2006, 51: 427
doi: 10.1016/j.pmatsci.2005.08.003
3
Xie J J, Wu X L, Hong Y S. Shear bands at the fatigue crack tip of nanocrystalline nickel [J]. Scr. Mater., 2007, 57: 5
doi: 10.1016/j.scriptamat.2007.03.027
4
Kumar K S, Suresh S, Chisholm M F, et al. Deformation of electrodeposited nanocrystalline nickel [J]. Acta Mater., 2003, 51: 387
doi: 10.1016/S1359-6454(02)00421-4
5
Farkas D, Van Petegem S, Derlet P M, et al. Dislocation activity and nano-void formation near crack tips in nanocrystalline Ni [J]. Acta Mater., 2005, 53: 3115
doi: 10.1016/j.actamat.2005.02.012
6
Pippan R, Hohenwarter A. The importance of fracture toughness in ultrafine and nanocrystalline bulk materials [J]. Mater. Res. Lett., 2016, 4: 127
pmid: 27570712
7
Wu X L, Zhu Y T. Heterogeneous materials: A new class of materials with unprecedented mechanical properties [J]. Mater. Res. Lett., 2017, 5: 527
doi: 10.1080/21663831.2017.1343208
8
Lu K. Making strong nanomaterials ductile with gradients [J]. Science, 2014, 345: 1455
doi: 10.1126/science.1255940
pmid: 25237091
9
Cheng Z, Zhou H F, Lu Q H, et al. Extra strengthening and work hardening in gradient nanotwinned metals [J]. Science, 2018, 362: eaau1925
doi: 10.1126/science.aau1925
10
Calcagnotto M, Adachi Y, Ponge D, et al. Deformation and fracture mechanisms in fine- and ultrafine-grained ferrite/martensite dual-phase steels and the effect of aging [J]. Acta Mater., 2011, 59: 658
doi: 10.1016/j.actamat.2010.10.002
11
Park K, Nishiyama M, Nakada N, et al. Effect of the martensite distribution on the strain hardening and ductile fracture behaviors in dual-phase steel [J]. Mater. Sci. Eng., 2014, A604: 135
12
Ma X L, Huang C X, Moering J, et al. Mechanical properties of copper/bronze laminates: Role of interfaces [J]. Acta Mater., 2016, 116: 43
doi: 10.1016/j.actamat.2016.06.023
13
Wang Y M, Chen M W, Zhou F H, et al. High tensile ductility in a nanostructured metal [J]. Nature, 2002, 419: 912
doi: 10.1038/nature01133
14
Zhu Y T, Wu X L. Perspective on hetero-deformation induced (HDI) hardening and back stress [J]. Mater. Res. Lett., 2019, 7: 393
doi: 10.1080/21663831.2019.1616331
15
Wu X L, Yang M X, Yuan F P, et al. Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility [J]. Proc. Natl. Acad. Sci. USA, 2015, 112: 14501
doi: 10.1073/pnas.1517193112
16
Zhao H Z, You Z S, Tao N R, et al. Anisotropic toughening of nanotwin bundles in the heterogeneous nanostructured Cu [J]. Acta Mater., 2022, 228: 117748
doi: 10.1016/j.actamat.2022.117748
17
ASTM. Standard test method for measurement of fracture toughness [S]. West Conshchocken: American Society of Testing and Materials, 2015
18
Smith D L, Hoffman D W. Thin-film deposition: Principles and practice [J]. Phys. Today, 1996, 49: 60
Bakonyi I, Péter L. Electrodeposited multilayer films with giant magnetoresistance (GMR): Progress and problems [J]. Prog. Mater. Sci., 2010, 55: 107
doi: 10.1016/j.pmatsci.2009.07.001
21
Fang T H, Li W L, Tao N R, et al. Revealing extraordinary intrinsic tensile plasticity in gradient nano-grained copper [J]. Science, 2011, 331: 1587
doi: 10.1126/science.1200177
pmid: 21330487
22
Wu X L, Yang M X, Yuan F P, et al. Combining gradient structure and TRIP effect to produce austenite stainless steel with high strength and ductility [J]. Acta Mater., 2016, 112: 337
doi: 10.1016/j.actamat.2016.04.045
23
You Z S, Qu S D, Luo S S, et al. Fracture toughness evaluation of nanostructured metals via a contactless crack opening displacement gauge [J]. Materialia, 2019, 7: 100430
doi: 10.1016/j.mtla.2019.100430
24
Luo S S, You Z S, Lu L. Intrinsic fracture toughness of bulk nanostructured Cu with nanoscale deformation twins [J]. Scr. Mater., 2017, 133: 1
doi: 10.1016/j.scriptamat.2017.01.032
25
Ashby M F. The deformation of plastically non-homogeneous materials [J]. Philos. Mag., 1970, 21: 399
26
Fleck N A, Muller G M, Ashby M F, et al. Strain gradient plasticity: theory and experiment [J]. Acta Metall. Mater., 1994, 42: 475
doi: 10.1016/0956-7151(94)90502-9
27
Gao H J, Huang Y G. Geometrically necessary dislocation and size-dependent plasticity [J]. Scr. Mater., 2003, 48: 113
doi: 10.1016/S1359-6462(02)00329-9
28
Mughrabi H. On the role of strain gradients and long-range internal stresses in the composite model of crystal plasticity [J]. Mater. Sci. Eng., 2001, A317: 171
29
Mughrabi H. The effect of geometrically necessary dislocations on the flow stress of deformed crystals containing a heterogeneous dislocation distribution [J]. Mater. Sci. Eng., 2001, A319-321: 139
30
Wu H, Fan G H. An overview of tailoring strain delocalization for strength-ductility synergy [J]. Prog. Mater. Sci., 2020, 113: 100675
doi: 10.1016/j.pmatsci.2020.100675
31
Yang M X, Pan Y, Yuan F P, et al. Back stress strengthening and strain hardening in gradient structure [J]. Mater. Res. Lett., 2016, 4: 145
doi: 10.1080/21663831.2016.1153004
32
Wang Y F, Yang M X, Ma X L, et al. Improved back stress and synergetic strain hardening in coarse-grain/nanostructure laminates [J]. Mater. Sci. Eng., 2018, A727: 113
33
Cao Z, Cheng Z, Xu W, et al. Effect of work hardening discrepancy on strengthening of laminated Cu/CuZn alloys [J]. J. Mater. Sci. Technol., 2022, 103: 67
doi: 10.1016/j.jmst.2021.06.043
34
Wan T, Cheng Z, Bu L F, et al. Work hardening discrepancy designing to strengthening gradient nanotwinned Cu [J]. Scr. Mater., 2021, 201: 113975
doi: 10.1016/j.scriptamat.2021.113975
35
Lu K, Lu L, Suresh S. Strengthening materials by engineering coherent internal boundaries at the nanoscale [J]. Science, 2009, 324: 349
doi: 10.1126/science.1159610
pmid: 19372422
36
Lu K, Yan F K, Wang H T, et al. Strengthening austenitic steels by using nanotwinned austenitic grains [J]. Scr. Mater., 2012, 66: 878
doi: 10.1016/j.scriptamat.2011.12.044
37
Xiong L, You Z S, Qu S D, et al. Fracture behavior of heterogeneous nanostructured 316L austenitic stainless steel with nanotwin bundles [J]. Acta Mater., 2018, 150: 130
doi: 10.1016/j.actamat.2018.02.065
38
You Z S, Luo S S, Lu L. Size effect of deformation nanotwin bundles on their strengthening and toughening in heterogeneous nanostructured Cu [J]. Sci. China Technol. Sci., 2021, 64: 23
doi: 10.1007/s11431-020-1584-6
39
Yan F K, Liu G Z, Tao N R, et al. Strength and ductility of 316L austenitic stainless steel strengthened by nano-scale twin bundles [J]. Acta Mater., 2012, 60: 1059
doi: 10.1016/j.actamat.2011.11.009
40
Zhang Y, Tao N R, Lu K. Mechanical properties and rolling behaviors of Nano-grained copper with embedded nano-twin bundles [J]. Acta Mater., 2008, 56: 2429
doi: 10.1016/j.actamat.2008.01.030
41
Yan F, Zhang H W, Tao N R, et al. Quantifying the microstructures of pure cu subjected to dynamic plastic deformation at cryogenic temperature [J]. J. Mater. Sci. Technol., 2011, 27: 673
doi: 10.1016/S1005-0302(11)60124-2
42
Yan F K, Tao N R, Archie F, et al. Deformation mechanisms in an austenitic single-phase duplex microstructured steel with nanotwinned grains [J]. Acta Mater., 2014, 81: 487
doi: 10.1016/j.actamat.2014.08.054
43
Li Q, Yan F K, Tao N R, et al. Deformation compatibility between nanotwinned and recrystallized grains enhances resistance to interface cracking in cyclic loaded stainless steel [J]. Acta Mater., 2019, 165: 87
doi: 10.1016/j.actamat.2018.11.033
44
You Z S, Li X Y, Gui L J, et al. Plastic anisotropy and associated deformation mechanisms in nanotwinned metals [J]. Acta Mater., 2013, 61: 217
doi: 10.1016/j.actamat.2012.09.052
45
Zhao H Z, You Z S, Tao N R, et al. Anisotropic strengthening of nanotwin bundles in heterogeneous nanostructured Cu: Effect of deformation compatibility [J]. Acta Mater., 2021, 210: 116830
doi: 10.1016/j.actamat.2021.116830
46
Ritchie R O. The conflicts between strength and toughness [J]. Nat. Mater., 2011, 10: 817
doi: 10.1038/nmat3115
pmid: 22020005
47
Lesuer D R, Syn C K, Sherby O D, et al. Mechanical behaviour of laminated metal composites [J]. Int. Mater. Rev., 1996, 41: 169
doi: 10.1179/imr.1996.41.5.169
48
Hunt W H, Osman T M, Lewandowski J J. Micro- and macrostructural factors in DRA fracture resistance [J]. JOM, 1993, 45(1): 30
49
Dehm G, Jaya B N, Raghavan R, et al. Overview on micro- and nanomechanical testing: New insights in interface plasticity and fracture at small length scales [J]. Acta Mater., 2018, 142: 248
doi: 10.1016/j.actamat.2017.06.019
50
Liu B X, Huang L J, Rong X D, et al. Bending behaviors and fracture characteristics of laminatedductile-tough composites under different modes [J]. Compos. Sci. Technol., 2016, 126: 94
doi: 10.1016/j.compscitech.2016.02.011
51
Pippan R. The crack driving force for fatigue crack propagation [J]. Eng. Fract. Mech., 1993, 44: 821
doi: 10.1016/0013-7944(93)90208-A
52
Wang Y Q, Fritz R, Kiener D, et al. Fracture behavior and deformation mechanisms in nanolaminated crystalline/amorphous micro-cantilevers [J]. Acta Mater., 2019, 180: 73
doi: 10.1016/j.actamat.2019.09.002
53
Ohashi Y, Wolfenstine J, Koch R, et al. Fracture behavior of a laminated steel-brass composite in bend tests [J]. Mater. Sci. Eng., 1992, A151: 37
54
Cepeda-Jiménez C M, García-Infanta J M, Pozuelo M, et al. Impact toughness improvement of high-strength aluminium alloy by intrinsic and extrinsic fracture mechanisms via hot roll bonding [J]. Scr. Mater., 2009, 61: 407
doi: 10.1016/j.scriptamat.2009.04.030
55
Venkateswara Rao K T, Yu W K, Ritchie R O. Cryogenic toughness of commercial aluminum-lithium alloys: Role of delamination toughening [J]. Metall. Trans., 1989, 20A: 485
56
Liu L, Yu Q, Wang Z, et al. Making ultrastrong steel tough by grain-boundary delamination [J]. Science, 2020, 368: 1347
doi: 10.1126/science.aba9413
pmid: 32381592
57
Cepeda-Jiménez C M, Pozuelo M, García-Infanta J M, et al. Influence of the alumina thickness at the interfaces on the fracture mechanisms of aluminium multilayer composites [J]. Mater. Sci. Eng., 2008, A496: 133
58
Kum D W, Oyama T, Wadsworth J, et al. The impact properties of laminated composites containing ultrahigh carbon (UHC) steels [J]. J. Mech. Phys. Solids, 1983, 31: 173
doi: 10.1016/0022-5096(83)90049-2
59
Lee S, Oyama T, Wadsworth J, et al. Impact properties of a laminated composite based on ultrahigh carbon steel and brass [J]. Mater. Sci. Eng., 1992, A154: 133
60
Zhang J Y, Zhang X, Wang R H, et al. Length-scale-dependent deformation and fracture behavior of Cu/X (X = Nb, Zr) multilayers: The constraining effects of the ductile phase on the brittle phase [J]. Acta Mater., 2011, 59: 7368
doi: 10.1016/j.actamat.2011.08.016
61
Nasim M, Li Y C, Wen M, et al. A review of high-strength nanolaminates and evaluation of their properties [J]. J. Mater. Sci. Technol., 2020, 50: 215
doi: 10.1016/j.jmst.2020.03.011
Zhang J Y, Liu G, Zhang X, et al. A maximum in ductility and fracture toughness in nanostructured Cu/Cr multilayer films [J]. Scr. Mater., 2010, 62: 333
doi: 10.1016/j.scriptamat.2009.10.030
64
Qin E W, Lu L, Tao N R, et al. Enhanced fracture toughness and strength in bulk nanocrystalline Cu with nanoscale twin bundles [J]. Acta Mater., 2009, 57: 6215
doi: 10.1016/j.actamat.2009.08.048
