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Accumulative roll bonding (ARB) is a repeated cladding process in which two or more sheets of material are joined together by rolling at temperatures below recrystallization. The present review is focused on ARB of high‐alloy steels, which, among other laminated metal composites (LMCs), deliver the highest mechanical properties. After a brief description of high‐strength steels, history, and state of the art of LMCs, the principal roll bonding mechanism is explained. Further, the methodology of ARB of steels and variable parameters (stacking, temperature, etc.) are discussed. Known examples of steel–steel laminates are summarized with respect to their rolling temperature and mechanical properties. Further, the main toughening mechanisms of steel‐based LMCs are listed. The most promising candidates of high‐alloy steel laminates are presented in more detail. The important deformation mechanisms of twinning‐ and transformation‐induced plasticity (TWIP and TRIP) high‐alloy steels are explained. Microstructural changes and layer bonding as well as mechanical properties and damage behavior of two‐ and four‐layered TRIP/TWIP steel laminates are illustrated, including some specific phenomena, such as deformation lenses. Finally, by summarizing the analyzed data on steel laminates, conclusions and outlook are formulated. [ABSTRACT FROM AUTHOR]

The initial thickness ratio and number of layers of dissimilar metal components greatly influence the impact performance of laminated metal composites. In this paper, positive and lateral impact tests of 5-layer composite sheets with thickness ratios of 3:1, 1.35:1, and 1:2 and 80-layer composite sheets prepared by ARB (accumulative roll bonding) were conducted to study the influences of the thickness ratio and layer number on the impact fracture behavior of composite sheets. The results showed that the higher the proportion of AA7075, the higher the bending strength of the AA6061/AA7075 laminated composite sheet; compared with the 5-layer composite sheet, the side impact performance of the 80-layer composite sheet is obviously improved, and its side impact strength, energy absorbed in the crack initiation stage, and crack propagation stage are better than those of the 5-layer composite sheet. In addition, the toughening mechanism of the 80-layer composite sheet is mainly that the increase in the number of layers makes the cracks deflect more frequently. Under the rapid impact load, the impact energy absorbed by the sample increases with the increase in the number of layers. [ABSTRACT FROM AUTHOR]

Laminated metal composites (LMCs) are a unique composite material and have great application prospects in automobiles, ships, aircraft, and other manufacturing industries. As lightweight materials, the Mg/Al LMCs are expected to combine the advantages of both Mg and Al alloys to broaden their application prospects. Roll-bonding is the most popular process for the fabrication of Mg/Al LMCs due to high production efficiency and good product quality stability. The roll-bonding process involves the deformation of the substrates and the formation of the interfacial diffusion layer. The latter will directly determine the interface bonding strength of Mg/Al LMCs. Bonding strength is very sensitive to the thickness of the reaction layer in the diffusion layer. When the thickness of the reaction layer exceeds 5 µm, the bonding strength decreases sharply. Therefore, controlling the thickness of the reaction layer is very important for the design of rolling parameters. The latest research also showed that the addition of intermediate layer metal and the construction of three-dimensional interfaces can further improve the interface bonding strength. How to apply these methods to roll-bonding is the focus of future research. Recently, a new rolling technique, corrugated roll/plat roll rolling+flat roll/flat roll rolling has been developed to fabricate Mg/Al LMCs. It can effectively promote the deformation of the hard layer and generate a wavy interface, resulting in the enhancement of the bonding quality and rolling quality. In the current review, the effects of rolling parameters and subsequent annealing on the interface structure of Mg/Al LMCs were elaborated in detail. The application of some special rolling techniques in the preparation of Mg/Al LMCs was also summarized. The latest research results on the relationship between interface structure and mechanical properties of Mg/Al LMCs were reviewed. Finally, further research directions in this field were proposed. [ABSTRACT FROM AUTHOR]

Fatigue of metallic components is an important aspect in mechanical engineering. For example, the repeated pressure differences result in the fatigue of the fuselage of aircrafts. These high demands require the application of endurable and lightweight materials. In this context, laminated metal composites produced by the accumulative roll bonding process can fulfill both aspects: outstanding mechanical strength of lightweight materials, due to an ultrafine‐grained microstructure, combined with the possibility to produce fatigue‐resistant materials by varying the stacking order of the laminated metal composites. This work investigates laminated metal composites consisting of aluminum AA2024 and titanium grade 1 layers with different stacking orders in respect to their three‐point bending fatigue properties. Additional finite element method (FEM) calculations of the stress distributions in the laminated metal composites are used to explain the results. The mechanical properties of the laminates with an outer aluminum or titanium layer are discussed based on the investigations of nanohardness and crack propagations. Although maximum bending stresses at the sheet surface of laminates with outer Titanium layer are higher than in monolithic materials, these laminates exhibit good lightweight potentials due to the weight reducing aluminum in inner layers. [ABSTRACT FROM AUTHOR]

Laminated metal composites have become a key strategy for the design and manufacture of metal parts with multiple combinations of excellent properties. This paper utilizes the differences in mechanical properties and recrystallization behavior of component metals to prepare a novel 316 L/(316 L-2.5 wt%Gd)/316 L neutron shielding laminated metal composites (LMCs) through composite rolling and solution treatment processes. LMCs have an excellent combination of properties: high strength (tensile strength: 571.36 MPa), sufficient tensile ductility (fracture elongation: 60 %) and high neutron shielding properties (thermal neutron shielding rate: > 90 %). Specifically, compared to the non-composite 316 L-2.5 wt%Gd neutron shielding material, the strength of the hot-rolled LMCs has increased by 2.0 times, and the elongation at fracture has improved by 3.3 times. After solid solution treatment, the elongation of LMCs is further increased, which is 6 times higher than non-composite 316 L-2.5 wt%Gd neutron shielding materials. The specially designed soft-hard matched 316 L/(316 L-2.5 wt%Gd) heterogeneous interfaces achieved good metallurgical bonding, with significant differences in grain sizes and strains. The main reasons for the enhanced strength and plasticity of LMCs are the geometric constraints caused by the layered structure composed of ductile and brittle metallic components, as well as the back-stress strengthening and strain hardening induced by deformation incompatibility at the heterogeneous interface. • 316 L/(316 L-2.5 wt%Gd) heterogeneous interfaces with different grain sizes and obvious differences in strains were constructed. • Heterogeneous structure and interfacial constraints synergistically enhance the strength and plasticity of 316 L/(316 L-2.5 wt%Gd)/316 L laminated composites. • Provides a promising solution to the difficult problem of mutual constraints between neutron shielding properties and mechanical properties. [ABSTRACT FROM AUTHOR]

The service life of technical components is often limited by the fatigue strength of the deployed materials. The accumulative roll bonding (ARB) process, which has the ability to produce ultrafine‐grained (UFG) laminated metal composites with tailored properties, offers a unique method to significantly enhance the fatigue life of materials that are cyclically loaded in three‐point bending. Detailed microstructural investigations reveal the material‐ and load‐specific deformation and damage mechanisms. Composites that have a sufficiently high difference in strength between the different constituent layers exhibit a significantly impeded crack growth and therefore an extended fatigue life at high stress amplitudes compared with those laminates with a rather similar strength of the different constituents. In the former composites, the fatigue crack is deflected at the material interface as it propagates from the softer to the harder layer. At low stress amplitudes, a prolonged fatigue life of the composites is mainly because of a significantly increased resistance to crack initiation. On the one side, this is as a result of the introduction of an UFG microstructure. On the other side, a load transfer toward stiffer layers in the interior of the composites also accounts for the enhanced fatigue life, if elastically dissimilar materials are combined in the right manner. [ABSTRACT FROM AUTHOR]

In this study, the effect of layer structure on the mechanical behavior of Ti/Al laminated metal composites (LMCs) was explored, focusing on the occurrence of an additional strengthening mechanism introduced by heterogeneous microstructures between constituent layers. Experimental results showed that the change in layer structure parameters and rolling conditions had a significant effect on the microstructure of the Al layer, and the difference in shear strain scale near the interface led to the formation of a grain refinement zone (GRZ) with various microstructural characteristics during dynamic recrystallization. In addition, the recrystallized distribution and texture evolution (i.e., the increasing recrystallized fraction and the intensifying shear texture r-Cube {001} 〈110〉) revealed that the deformation storage energy as the driving force of recrystallization played an important role in the difference in the heterogeneous degree formed in various Ti/Al LMCs. On the other hand, the strength deviation between the experimental strength and the theoretical strength predicted by the rule of mixture can be detected in all LMCs with different thickness ratios after hot rolling, resulting from the pile-up of geometrically necessary dislocations (GNDs) caused by the synergetic deformation induced by mechanical incompatibility between Ti and Al layers during plastic deformation. With a change in the layer structure parameter, a considerable strength deviation in the Ti/Al LMC with a large thickness ratio indicated that the high mechanical incompatibility between the constituent layers was conducive to the enhancement of additional strengthening behavior. • Microstructural evolution and mechanical behavior of Ti/Al LMCs with various layer structures were explored. • The formation of grain refinement zone near the interface with various microstructural characteristics was analyzed • The contribution of interfacial effect introduced by mechanical incompatibility on properties were investigated. [ABSTRACT FROM AUTHOR]

The layer thickness has been reported to play a crucial role in laminated metal composites (LMCs). In this work, Al/Ti/Al LMCs with varying Ti layer thickness but a constant number of interface were fabricated by hot rolling and annealing to explore the effect of layer thickness on the enhanced strength and ductility. Ex-situ electron backscatter diffraction (EBSD) and digital image correlation (DIC) techniques were used to reveal the plastic deformation mechanisms. With the decrease of the Ti layer thickness, the extra strength and elongation caused by the layered structure increase continuously until the layer thickness is reduced to ∼0.6 mm. When the best combination of strength and elongation is achieved, the width of the interface affected zone (IAZ) in the Ti layer reaches ∼0.3 mm, which is roughly half of the layer thickness of the Ti layer. Within the IAZ of the Ti layer, more pyramidal and basal slips are activated compared with that in the central part, which contributes to the increase of strain delocalization efficiency. In addition, the geometrically necessary dislocations (GNDs) also exhibit gradient distribution following the strain gradient, resulting in hetero-deformation induced (HDI) strengthening and hardening. This work further enriches the knowledge of achieving excellent strength-ductility synergy in LMCs. [ABSTRACT FROM AUTHOR]

Although laminated metal composites fabricated by accumulative roll bonding (ARB) undergo kink-band formation, there are no guidelines for optimizing their fabrication to avoid necking and shear localization without post-annealing. The necking of the composite layers during rolling generates non-uniformities that may degrade the mechanical performance of the composite. This paper proposes a model for laminated metal composites that aims to quantitatively assess and predict necking based on the work-hardening of each layer. Cu–Al-, Cu–A5052-, and Cu–A5083-laminated metal composites were fabricated using ARB at room temperature (~300 K) without post-annealing, and they were subjected to mechanical and microstructural analyses. A normalized neck amplitude was introduced as a new parameter that accurately predicted the degree of necking observed experimentally. Another new parameter, an instability index , was introduced to frame the necking criterion of the hard layers. A plastic instability criterion framed based on the new parameters accurately predicted the degree of necking in the hard layers of the as-prepared laminated metal composites. These findings may be applied to guide the fabrication of metal composites of any composition using the ARB process. [Display omitted] • Laminated metal composites (LMCs) were fabricated using ARB without post-annealing. • Normalized neck amplitude can assess the experimentally observed degree of necking. • Instability index predicts the necking of the hard layers in the LMCs. • These two parameters aid in framing plastic instability criterion for LMCs. • The findings are instrumental in fabricating stable LMCs using ARB. [ABSTRACT FROM AUTHOR]

Improving the strength and ductility of magnesium (Mg) alloys is a popular area of research. Many studies have indicated that laminated metal composites can be used to simultaneously yield excellent properties of all their constitutive metals. In this study, laminated Mg/Zr (AZ31/Zr702/AZ31) composites were fabricated by hot rolling-induced bonding. An Mg plate was used as the initial wedge component to obtain a wide range of rolling reductions (40%–70%) in a given Mg/Zr composite, and its microstructures and mechanical properties were then characterized. The results show that rolling reduction greater than 40% was needed to achieve a well-bonded interface for Mg/Mg (AZ31/AZ31) and Mg/Zr composites when rolled at 400 °C. With increasing rolling reduction, the strength of the Mg/Zr composite (∼180 MPa) showed no prominent change, and was higher than that of Mg/Mg composites (∼150 MPa) fabricated by using the same bonding process. In addition, the Mg/Zr composite had significantly higher bonding strength (∼6 N/mm) and ultimate peel strength (∼9 N/mm) than the Mg/Mg composites (∼2.5 N/mm and ∼3 N/mm). Finite element simulations were also used to examine the underlying strengthening mechanisms of the composites. The results here contribute to research on the strengthening and toughening of Mg alloys as well as the fabrication of laminated metal composites. [ABSTRACT FROM AUTHOR]

The effects of changing the test temperature from room temperature to 373 or 398 K on the fatigue crack propagation of 6090/SiC/25p-6013 and 7093/SiC/25p-7093 laminates tested in the crack arrestor orientation was investigated. The fatigue crack propagation behaviour of the individual monolithic and discontinuously reinforced aluminium alloy (DRA) layers was additionally compared to that of the laminates. The fatigue behaviour of the laminates was significantly different than that of the individual layers and was affected by changes in the test temperature as well as by a thermal exposure to high temperatures (e.g. 373 or 398 K) before testing at 298 K. Significant changes in the crack velocity also occurred upon traversing from one layer to another for the fatigue tests conducted at high temperature, or after exposure to high temperature. [ABSTRACT FROM AUTHOR]

The effect of processing variables on the growth of a titanium aluminide layer produced from elemental titanium and aluminum foils was examined, with the intention of yielding a titanium–titanium aluminide composite structure. To produce the intermetallic phase in situ, two processing techniques were employed, diffusion bonding and combustion synthesis. Microstructural examination of the titanium aluminide layer revealed striking similarities in the resulting morphology yielded by both processing techniques, in particular for those samples diffusion annealed at lower temperatures (615 °C and below) and those reacted by combustion synthesis. In both cases, an exothermic chemical reaction was responsible for aluminide formation in specimens, and in those samples processed by diffusion bonding, this reaction was observed to be rate controlled by a diffusion mechanism. Chemical analysis of the product aluminide showed the layers to be composed completely of a single phase, TiAl3, which is believed to be the result of thermodynamic stability of this phase relative to other stable equilibrium phases in the titanium aluminum system. The results of these experiments are discussed with a view of utilizing these processes to optimize the mechanical behavior of titanium aluminide by incorporating it into a laminated metal composite. [Copyright &y& Elsevier]

Laminated metal composites are a promising design since the hybrid design enables superior and tailorable material properties compared with bulk material. The article introduces for the first time, laminated metal composites consisting of multiple bilayers of alternating layers of ductile and high-strength steel processed by wire arc additive manufacturing (WAAM). The layup of the laminated metal composites is built up by alternating deposits made of ductile steel and high-strength steel type wires. Governing parameters in the fabrication process affecting the material properties, such as dilution, are discussed. Enhanced material properties of the laminated metal composites fabricated by WAAM are investigated under static tensile, impact and tension-tension high-cycle-fatigue loading and compared to the relating homogenous weld metal. Potential reasons for the retardation of crack propagation in laminated metal composites fabricated by WAAM compared to findings in roll-bonded laminated metal composites are discussed. WAAM is conducted by a collaborative robot providing a high level of flexibility in respect to geometry and scalability. Tailorability of material properties through WAAM-fabricated laminated metal composites adds an important layer of flexibility which has not been explored yet. [ABSTRACT FROM AUTHOR]

In the present work, laminated Cu/Ni samples reinforced by graphene film with various thicknesses were produced via electrophoretic depositing graphene oxide (GO) on Cu foil by controlling deposition voltage, and the effect of thickness of graphene film on strengthening Cu/Ni multilayer composites were investigated in detail. Microstructural examination revealed that the fragments of graphene film were dispersed at the interface between Cu and Ni layer after hot rolling, with a range of thickness from 0.76 to 5.13 μm. The graphene film showed an excellent strengthening effect in the composites regardless of their thickness according to the tensile testing. However, the toughing effect achieved optimal as the thickness of 4.12 μm. The role of deposited graphene film played in determining the load transfer and optimizing the interface was discussed. Graphene film with appropriate thickness can effectively inhibit the severe asymmetric diffusion behavior of Cu and Ni elements, which plays an important role in strengthening and toughening clad interfaces by inhibiting the formation of Kirkendall voids. This study provides novel insights into understanding the strengthening and toughing behaviors of graphene reinforced multilayer composites, which can be developed into a technical strategy for fabricating high performance laminated metal matrix composites. [ABSTRACT FROM AUTHOR]

Multilayer metal composites have great application prospects in automobiles, ships, aircraft and other manufacturing industries, which reveal their superior strength, toughness, ductility, fatigue lifetime, superplasticity and formability. This paper presents the various mechanical properties, deformation characteristics and strengthening–toughening mechanisms of laminated metal matrix composites during the loading and deformation process, and that super-high mechanical properties can be obtained by adjusting the fabrication process and structure parameters. In the macroscale, the interface bonding status and layer thickness can effectively affect the fracture, impact toughness and tensile fracture elongation of laminated metal matrix composites, and the ductility and toughness cannot be fitting to the rule of mixture (ROM). However, the elastic properties, yield strength and ultimate strength basically follow the rule of mixture. In the microscale, the mechanical properties, deformation characteristics, fracture behavior and toughening mechanisms of laminated composites reveal the obvious size effect. [ABSTRACT FROM AUTHOR]

This study presents a method to obtain aluminum alloy laminated composites with high yield strength and good ductility through a multiscale coarse/ultrafine-grained design, which are fabricated by accumulative roll bonding (ARB) and subsequent annealing treatment. Experimental results showed that an outstanding combination of strength and ductility was achieved in 1100/7075 Al alloy laminated composites after annealing at 300 °C for 60 min. Deviation between experimental and predicted results from stress-strain curves indicated that an extra strengthening effect was present in the laminated metal composites. Moreover, to analyze the effect of the magnitude of mechanical incompatibility on the mechanical properties during deformation, laminated metal composites with constituent layers possessing different flow properties were comparatively studied. Laminated metal composites with multiscale grain size distributions were obtained using different rolling strain paths and annealing treatments, which was attributed to differences in the recrystallization of constituent metals. It was determined that cross rolling, compared with direct rolling, gave rise to more effective improvements in the mechanical properties after annealing treatments due to higher mechanical incompatibility across the interface. For the Al alloy laminated composites, the difference in flow properties between the constituent layers plays an important role in additional interfacial strengthening by appropriate collocation of component strengths. During tensile deformation, a high density of geometrically necessary dislocations (GNDs) was distributed in the interface of the soft layer due to the mechanical incompatibility across the interface. The high yield strength with a multiscale interfacial structure is attributed to the back stress strengthening associated with the formation of GNDs and the good ductility results from the high strain hardening rate during plastic deformation. [ABSTRACT FROM AUTHOR]