scispace - formally typeset
Journal ArticleDOI: 10.1016/J.MSEA.2021.140830

Enhancing strength-ductility synergy of carbon nanotube/7055Al composite via a texture design by hot-rolling

S. Bi1, S. Bi2, Z.Y. Liu1, B.L. Xiao1  +5 more
Abstract: The limited ductility of carbon nanotubes reinforced Al matrix (CNT/Al) composites hinders their engineering applications, which is an urgent problem to be solved. Herein, texture optimization through hot-rolling was employed to improve the strength-ductility of the CNT/7055Al composites. Microstructural examinations indicate that the composite subjected to extrusion (CNT/7055Al-E) had a bimodal structure with the coarse and ultrafine grains. The composite subjected to extrusion followed by hot-rolling (CNT/7055Al-ER) exhibited a uniform ultrafine grain structure. No further structure damage or aggregation was detected for the CNTs after hot-rolling. The texture analysis demonstrates that the CNT/7055Al-E had a fiber texture, while the CNT/7055Al-ER had a plate texture including {011} , {113} and {215} components with higher texture intensity. Compared with the CNT/7055Al-E, the CNT/7055Al-ER increased twofold in elongation with a slight decrease in strength, which was attributed to the favorable grain orientations, the increased proportion of low angle grain boundaries, as well as the fine and densely distributed precipitates. Further, the mechanical property anisotropy of the composite was weakened after hot-rolling due to the elimination of coarse grain bands.

... read more

Topics: Texture (crystalline) (57%), Grain boundary (54%), Composite number (51%) ... read more
Citations
  More

6 results found


Journal ArticleDOI: 10.1016/J.CARBON.2021.08.034
S. Bi1, S. Bi2, Z.Y. Liu1, B.L. Xiao1  +5 moreInstitutions (2)
30 Oct 2021-Carbon
Abstract: Understanding the fatigue behavior of Carbon nanotube (CNT) reinforced Al composites (CNT/Al) was of critical importance, for their further application in the aerospace industry. Although CNT could improve the fatigue performance, the fatigue behavior of CNT/Al composites with different structure (e.g. bimodal structure) under different fatigue conditions was still in lacking. In this study, the tension-tension/tension-compression fatigue behaviors of bimodal structure CNT/7055Al composites consisting of ultra-fine grain (UFG) zones rich of CNTs and coarse grain (CG) bands free of CNTs, were investigated and the corresponding damage mechanisms were analyzed. Results indicated that dislocation cells, tangles and subgrains were observed in the CGs, while no obvious dislocation configuration was detected in the UFGs after 107 fatigue cycles. Under the tension-tension fatigue condition, the fatigue strength of the composites was increased from 350 MPa to 400 MPa by load transfer effect of CNTs at 107 cycles. However, CNTs failed to improve the fatigue strength under the tension-compression fatigue condition due to the failure of the UFG zones rich of CNTs resulting from the high stress amplitude. It was found that strain localization in the CGs was the principal damage mechanism of CNT/7055Al composites.

... read more

Topics: Fatigue limit (63%)

1 Citations


Journal ArticleDOI: 10.1016/J.COMPOSITESB.2021.109094
K. Ma1, K. Ma2, X. N. Li2, Kun Liu1  +4 moreInstitutions (2)
Abstract: Heterogeneous structure consisting of brittle-zones (BZs) rich of carbon nanotubes (CNTs) and ductile-zones (DZs) free of CNTs, was an effective way to improve the strength-ductility of CNT reinforced Al (CNT/Al) composites. Two heterogeneous CNT/2009Al composites with coarse grain (CG, ~2 μm) DZs or ultra-fine grain (UFG, ~500 nm) DZs were fabricated and achieved enhanced strength-ductility. However, the heterogeneous composite with CG DZs had a lower high-cycle fatigue strength as well as fatigue strength/tensile strength ratio than the uniform composite, while the heterogeneous composite with UFG DZs exhibited the increased fatigue strength and the same level of fatigue strength/tensile strength ratio compared to the uniform composite. It was found that the improved fatigue properties for the heterogeneous composite with the UFG DZs could attribute to two reasons. Firstly, the UFG for the DZs significantly increased the strength of DZs, which effectively reduced the strain localization in the DZs. Secondly, the dislocations piling up at the grain boundaries of the BZs, as well as the stress concentration at the boundaries between the DZs and BZs were relieved due to the coordinated micro-strain for the heterogeneous structure. This provided a simple strategy for the structural design of heterogeneous composites with high fatigue strength.

... read more

Topics: Ultimate tensile strength (54%), Fatigue limit (52%), Stress concentration (52%) ... read more

1 Citations


Journal ArticleDOI: 10.1016/J.JMAPRO.2021.09.003
Abstract: In the present work, a novel hybrid manufacturing process is established to develop high performance AA6063/SiC nano-composite sheets. The novel hybrid manufacturing process consists of cryorolling (CR) followed by warm rolling (WR). The resultant effect of the hybrid processing route on the mechanical properties, strain hardening ability, microstructural evolution and age hardening response was studied in detail. The outcomes of the hybrid processing route showed a significant enhancement in strength of CR + WR nano-composites. The improvement in strength of CR + WR is due to the combined effect of increased dislocation density, dynamic recovery, grain refinement, and aging treatment. Imparting of optimum age hardening (A) treatment (150 °C for 4 h) to CR + WR nano-composite resulted in significant enhancement of strength-ductility combination which is found to be highest among the published literature on AA6XXX/SiC composites. The mechanical properties of peak aged CR + WR composites are also found to be higher than that of CR (90% cryorolled +Peak aged)) nano composite. The scientific knowhow and governing mechanisms were established to understand the potential of hybrid manufacturing process on significant enhancement of mechanical properties and age hardening response on AA6063/SiC nano-composites.

... read more


Book ChapterDOI: 10.1007/978-3-030-79165-0_5
28 Jun 2021-
Abstract: Carbon nanotube reinforced aluminum matrix composites are considered a promising solution for applications that require high specific mechanical properties. Even though there are numerous methods for their manufacturing, these are frequently based on powder metallurgy approaches, limiting the fabrication of components with significant volumes and complex shapes. Casting, as a manufacturing technique, is regarded as the most appropriate route to obtain complex-shaped components with a relative high microstructural quality. These techniques to obtain Al-CNT cast components is still challenging due to the agglomeration, lack of dispersion, reduced bonding and density of the CNTs in Al. To address these issues, CNTs are usually pre-processed by ball-milling with Al powder to promote bonding and disperse the reinforcement, however, these techniques are not really beneficial to casting approaches due to the increase of Al2O3 content that do not disperse within the Al alloy melts. This study proposes the use of Al spheres (~1 mm) in these ball milling techniques to prevent significant plastic deformation, the formation of Al flakes and the increase in Al2O3 content. It is shown that CNTs may be dispersed and bonded to the Al sphere surfaces. Results suggest that this is a promising novel technique to allow a successful implementation of casting-based routes to fabricate high-volume and complex-shaped Al-CNT components.

... read more

Topics: Casting (59%), Powder metallurgy (51%)

Journal ArticleDOI: 10.1016/J.CARBON.2021.07.042
Pu Bowen1, Xiang Zhang1, Dongdong Zhao1, Chunnian He1  +4 moreInstitutions (1)
15 Oct 2021-Carbon
Abstract: Achieving uniform reinforcement dispersion and strong interfacial bonding remains challenging to increase the strengthening efficiency in advanced metal matrix composites (MMCs). In this work, we report the prominent strengthening efficiency in graphene nanosheet reinforced Al matrix (GNS/Al) composites fabricated via hybrid deformation combining hot extrusion and multi-pass hot rolling (MPHR). Results show that most GNS-rich zones in extruded GNS/Al composites were eliminated by MPHR, leading to an even layer-distribution of GNSs aligning along the Al grains, which initiates grain recrystallization and promotes dislocation accumulation for a high strain hardening of the composites. Moreover, the shear stress induced by MPHR was revealed to exfoliate overlapped GNSs to attach with Al and enhance the formation of boundary-like defects/disorders at the edge of GNSs, which promotes Al–C interdiffusion and generates the typically infiltrated Al-GNS interfaces featured by transition zones. Such unique interface structure exhibits a high interfacial shear strength, enabling the effective load transfer between GNSs and Al. It is confirmed that the fine distribution of GNS and robust Al-GNS interfacial cohesion contribute to the remarkable strengthening efficiency of GNSs. The present work paves a new way to disperse GNSs and tune interface structures for enhancing mechanical performance of Al matrix composites.

... read more


References
  More

55 results found


Journal ArticleDOI: 10.1016/0001-6160(53)90006-6
G.K Williamson1, W.H Hall1Institutions (1)
01 Jan 1953-Acta Metallurgica
Abstract: Methods of analysis previously used in the interpretation of line broadening are discussed and are shown to be inadequate; more reliable methods being outlined. An analysis of published results using one of these methods suggests that the observed effects can be attributed to simultaneous small particle size and strain broadening. Measurements of the changes in intensity distribution have been made, using a Geiger counter spectrometer, in the spectra of cold worked aluminium and wolfram. The line breadths may be attributed to simultaneous small particle size and strain broadening, the latter predominating, particularly at the higher Bragg angles, and it is shown that the observed effects are produced by dislocations or some similar structural fault. The observed rise in the breadths of the high angle lines from annealed materials suggests that some dislocations remain after annealing. Fourier analysis of the line shapes in general merely confirm the results of the analysis of the line breadths, but in the case of the recovered specimens it suggests that the dislocations form into walls (“polygonization”).

... read more

6,769 Citations


Journal ArticleDOI: 10.1038/NMAT4089
Ulrike G. K. Wegst1, Hao Bai2, Eduardo Saiz3, Antoni P. Tomsia2  +1 moreInstitutions (3)
01 Jan 2015-Nature Materials
Abstract: Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.

... read more

2,288 Citations


Journal ArticleDOI: 10.1016/J.MSER.2013.08.001
Sie Chin Tjong1, Sie Chin Tjong2Institutions (2)
Abstract: One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.

... read more

Topics: Carbon nanotube metal matrix composites (61%), Carbon nanotube (61%), Nanocomposite (56%) ... read more

686 Citations


Journal ArticleDOI: 10.1016/J.ACTAMAT.2004.06.017
Yonghao Zhao1, Xiaozhou Liao1, Z. Jin2, Ruslan Z. Valiev3  +1 moreInstitutions (3)
06 Sep 2004-Acta Materialia
Abstract: Microstructures and mechanical properties of equal-channel angular pressing (ECAP) processed and naturally aged ultrafine grained (UFG) and coarse grained (CG) 7075 Al alloys as well as their evolutions during annealing were investigated After the same natural aging, the tensile yield strength, ultimate strength, and microhardness of the UFG samples were 103%, 35%, and 48% higher, respectively, than those of the CG samples, because of higher densities of Guinier–Preston (G–P) zones and dislocations in the UFG sample Upon annealing, the microhardness of the UFG sample decreased gradually, while a hardening peak appeared for the CG sample The peak was caused by the precipitation hardening of the metastable η′ phase For the UFG sample, the precipitation hardening was overcompensated by the significant decrease of microstrain (dislocation density) upon annealing, resulting in a lack of precipitation hardening peak Differential scanning calorimetry indicates that the ECAP process only accelerated the phase precipitations, but did not change the sequence of phase precipitation This study shows that severe plastic deformation has the potential to significantly improve the mechanical properties of age-hardening Al alloys

... read more

655 Citations


Journal ArticleDOI: 10.1002/ADMA.200600310
Yonghao Zhao1, Xiaozhou Liao2, Sheng Cheng3, En Ma3  +1 moreInstitutions (3)
05 Sep 2006-Advanced Materials
Abstract: In this paper we report a strategy to simultaneously increase the ductility and strength of bulk nanostructured materials. By engineering very small second-phase particles into a nanostructured Al alloy matrix, we were able to more than double its uniform elongation, while further gaining rather than sacrificing its yield strength. The simultaneous enhancement of ductility and strength is due to the increased dislocation accumulation and resistance to dislocation-slip by second-phase particles, respectively. Our strategy is applicable to many nanostructured alloys and composites, and paves a way for their large-scale industrial applications. The material used in this model study is 7075 Al alloy. The alloy was solution-treated to obtain a coarse-grained (CG) solid solution. The CG sample was immediately cryogenically rolled to produce nanostructures with an average grain size of ca. 100 nm (designated as NS sample). The NS sample was then aged at low temperature to introduce very small secondphase particles (designated as NS+P sample). The engineering stress–strain curves of these samples are compared in Figure 1a. The 0.2 % yield strengths (marked by circles) of the CG, NS, and NS+P samples are 145 MPa, 550 MPa, and 615 MPa, respectively. Therefore, the low-temperature aging enhanced the yield strength of the NS sample by 12 %. The uniform elongation (marked by the symbol on the curves in Fig. 1a) was determined by the Considere criterion (Eq. 1) governing the onset of localized deformation [8]

... read more

Topics: Yield (engineering) (55%), Ductility (51%)

622 Citations