Roll-bonding Technique Research Articles

Fracture Toughness, Mechanical Properties and Bending Behavior of AA1050/ Mg AZ31B Sheets Fabricated by an Accumulative Roll Bonding Technique

Fracture Toughness, Mechanical Properties and Bending Behavior of AA1050/ Mg AZ31B Sheets Fabricated by an Accumulative Roll Bonding Technique

Does VIMC-FMC work well on highly ductile bimetal joints? An investigation on mixed mode I/II fracture of AA1050/Cu bimetal weakened by U-notches

In this study, it is attempted to check if the virtual isotropic material concept (VIMC), originally suggested for fiber-reinforced composite laminates, can be used as an appropriate simplifying tool in fracture estimation of notched bimetals. First, the aluminum alloy AA1050 and the copper are cladded together using the roll-bonding technique. Then, several U-notched bimetal specimens are manufactured to perform fracture tests under mixed mode I/II loading conditions. Due to the highly ductile behavior of the AA1050/Cu bimetal, the fictitious material concept (FMC) is adopted to equate the bimetal with a fictitious material having perfectly linear elastic behavior with the aim to avoid the elastoplastic fracture analysis. Finally, the VIMC and FMC are coupled with three famous brittle fracture models, i.e., the U-notch maximum tangential stress (UMTS), U-notch mean stress (UMS), and U-notch strain energy density (USED) criteria, for predicting the experimentally measured strength of the notched bimetal specimens. The results indicate that the maximum discrepancy between the theoretical predictions and the experimental results in all the combined failure criteria is less than 8%. Therefore, the VIMC-FMC combination is found to be quite effective as a converter to solve the complex problem of highly ductile fracture of notched inhomogeneous anisotropic bimetals under mixed mode I/II loading using only the linear elastic analysis of the fictitious homogeneous isotropic plates. Also, found in this research is that not only VIMC works well on fiber-reinforced composite laminates, but also on bimetal joints.

Notch strength evaluation for highly ductile Al/Cu bi-metal fabricated by the roll-bonding technique under pure mode I and pure mode II loading conditions

In this work, the aluminum alloy AA1050 and copper sheets are cladded together using the roll-bonding technique to make rectangular bi-metallic joints. To examine the notch strength of this bi-metal under quasi-static loading, central slits with two U-shaped ends are introduced into the bi-metal. The slit orientation angle is adopted such that for horizontal slit, the notched rectangular specimen experiences pure mode I loading. However, when the slit orientation angle changes to about 67 degrees, which is obtained by the finite element (FE) analysis, the U-ends of the slit are subjected to pure mode II loading. Considering three different notch tip radii, two loading conditions, and three replicates for each test configuration, totally 18 U-notched specimens are produced and tested with the goal to measure the notch strength of bi-metal experimentally. According to the experimental observations, the bi-metal joint is perfect such that crack initiates from the notch in the whole thickness, proposing that the whole bi-metal joint can be considered as a single bulk material. Based on these observations and thanks to the virtual isotropic material concept (VIMC), the AA1050/Cu bi-metal is firstly equated with a virtual bulk material having homogeneous and isotropic behavior. Secondly, due to highly ductile behavior of the bi-metal joint proven by the associated tensile stress–strain curve, the fictitious material concept (FMC) is used to equate the virtual isotropic material obtained from the previous step having elastoplastic behavior with a fictitious material having perfectly linear elastic behavior. Finally, the VIMC and FMC are linked to the U-notch maximum tangential stress (UMTS), U-notch mean stress (UMS), and U-notch strain energy density (USED) criteria to predict the notch strengths of the bi-metal joint experimentally measured. With always higher than 92% accuracy for all VIMC-FMC-UMTS, VIMC-FMC-UMS, and VIMC-FMC-USED combined criteria, it is shown that the two-level strategy of material simplification, i.e., VIMC-FMC, is quite successful to be combined with different brittle fracture criteria for predicting the notch strength of AA1050-Cu bimetals under both pure tensile and pure in-plane shear modes of loading.

Fabrication of Two Layers Al/Cu Metal Composite by Roll Bonding Technique

The sheet metal of two-layer composite (Al/Cu) is considered as one of the most important products used in different engineering applications. The roll bonding technique (RBT) is an active process to fabricate the metal composite due to the occurrence of high deformation that leads to layers bonding together. In this study, Al8112 and pure Cu were selected as the metals to create a sheet composite (Al8112/Cu) by employing RBT on the basis of one cycle at various thickness reductions (R%; 45%, 50%, 55%, and 60%) and bonding temperatures (T; 300 °C, 400 °C, and 450 °C). The microstructure behaviour was examined to check the overlap bonding area for the composite layers. Vickers microhardness and tensile tests were also performed to measure the hardness, yield strength, and tensile strength. The results revealed that the R% had a strong effect on the interface bonding zone and hardness. It also had a significant effect on yield and tensile strength. However, T had a small effect on the hardness and a disparate effect on the yield and tensile strength.

Morphology and properties of diamond-copper/steel matrix abrasive composites prepared by roll-bonding technique

Diamond-copper/steel matrix abrasive composites were prepared by the roll-bonding technique. Firstly, the effects of the roll-bonding technical parameters (including sintering parameters, rolling parameters, and the component content) on the interfacial bonding strength in the composites were researched. Then, the surface macroscopic characteristics of the composites and the microstructures of the bonding interfaces were observed. The static compressive strength of the diamonds in the composites and the grinding performance of the composites were measured. Finally, the mechanisms for the effects of the roll-bonding technical parameters on the interfacial bonding strength were explored. The results showed that with increasing those parameters, the interfacial bonding strength between diamonds and the matrices displayed an initial increase and then a significant decrease. Furthermore, the optimal interfacial bonding strength (11.4 kN/m) and an excellent grinding performance (abrasive ratio of 23.2) were obtained from the diamond-steel matrix composites containing 10 vol% binder and 25% concentration of diamonds, when sintered at the temperature of 900 °C for holding time of 30 min and cold rolled at the reduction rate of 70%. The composites prepared with the optimum technical parameters had acceptable surface smoothness. In addition, the diamonds could be dispersed homogeneously in the matrices and firmly adhered to the substrates. When the diamond concentration was 25% in cold-rolling, the diamond-steel matrix composites showed better grinding performance. By improving the pressure condition of metallurgical bonding between diamonds and metal matrices from static pressure to rolling dynamic pressure, the sintering condition of temperature and holding time can be reduced and shortened, and the sintering condition effect on the interfacial bonding can be weaken. Thus, the application of the roll-bonding technique to the preparation of diamond-metal matrix composites could effectively avoid the thermal damage of diamonds caused by sintering process.

Comparative Study of the Planar Uniformity of the Mechanical Properties of the AA1050 Strips Processed by Conventional and Cross Accumulative Roll-Bonding Techniques

In this research, a modified method of the conventional accumulative roll-bonding (ARB) process, named cross accumulative roll-bonding (CARB), was applied on an AA1050 strip for up to 13 cycles. The planar uniformity of the mechanical properties in the products of ARB and CARB processes has not been investigated yet. This article aims to compare the planar inhomogeneity of the tensile properties in different directions of the rolling plane of the ARB- and CARB-processed specimens. For this purpose, uniaxial tensile tests were performed in the rolling, transverse, and diagonal directions of the products. Furthermore, Vickers microhardness was used to investigate the hardness distribution throughout the thickness of specimens. The results revealed that the CARB process exhibited higher tensile strength, elongation, and hardness with more homogeneous distribution of the hardness and particularly better planar uniformity of the tensile properties compared with the conventional ARB process.

A top–down approach for the preparation of bulk layered metal/organic hybrid material

Although the potential of layered metal/organic hybrid material has long been recognized, manufacturing analogous materials in large-scale remains extremely difficult owing to the lack of a suitable fabrication process. Here, a top–down approach that combines accumulative roll bonding technique with selective etching and vacuum impregnation process was first developed to fabricate bulk layered Ta/polymer hybrid material with controlled layer thickness (h) of 100 μm ≥ h ≥ 1 μm. This approach can be generalized to fabricate other layered metal/polymer hybrid material with a large number of material combinations and a wide range of layer dimensions. This kind of material, which is comprised of hard and soft phases arranged in complex hierarchical architectures, has potential for application as lightweight and energy absorption structural materials.

Structure and mechanical properties of Ni/Ti multilayered composites produced by accumulative roll-bonding process

This research studies the structure and mechanical properties of Ni/Ti multilayered composites produced from commercial pure Ni and Ti foils by accumulative roll-bonding technique. To investigate these properties, scanning electron microscopy, Vickers microhardness, and uniaxial tensile tests were conducted at different processing cycles. Studies showed that in terms of structure, Ni and Ti layers maintain their continuity even up to 10 cycles of accumulative roll-bonding. Moreover, the energy-dispersive spectroscopy in scanning electron microscopy detected no deformation induced diffusion or reactive interfacial zones. It was found that by increasing the accumulative roll-bonding cycles, tensile and yield strengths as well as the hardness of the composite enhance and the total elongation reduces continuously.

Fine Texture Enhancement of Al-Mg-SC alloy by Using Cross Accumulative Roll Bonding Technique

Aluminum alloys were as a rule used to fabricate in a few car and aviation parts. Al-Mg-Sc combination sheets were prepared a couple of cycles of Cross accumulative roll bonding (CARB) & similarly of accumulative roll bonding (ARB). In these two procedures Micro-structural advance have been occurring. It was clearly observed microstructure depicted by checking electron microscopy (SEM). In the midst of these both the system, Al-Mg-Sc alloys was adequately made with no disfigurement. In the midst of CARB process, Reinforcement (Mg, SC) particles reliably scattered inside Al system differentiated and similarly examined Al-Mg-Sc alloys in ARB process. In these two procedures, to incorporating of minor Sc in Al-Mg was extended hardness and besides it credited to the fine surface development. TEM imaging demonstrates development of fine hastens shaped inside grid in CARB contrast and ARB amid heat treatment. The Al-Mg-Sc alloy hardness was evaluated with using a Vickers hardness analyzer.

Roll Bonding Properties of Al/Cu Bimetallic Laminates Fabricated by the Roll Bonding Technique

Roll bonding (RB) of bimetal laminates is a solid phase method of bonding and has been widely used in the manufacturing of layered strips. This process is widely used for brazing sheet for automotive, aerospace, vessel, and electrical industries. In this study, 1-mm bimetallic aluminum 1050 and pure copper (Al/Cu) laminates were produced using the roll bonding (RB) process. The RB process was carried out with thickness reduction ratios of 10%, 20%, and 30%, separately. Particular attention was focused on the bonding of the interface between Al and Cu layers. The optimization of thickness reduction ratios was obtained for the improvement of the bond strength of bimetallic laminates during the RB process. Also, the RB method was simulated using finite element simulation in ABAQUS software. Finite Element (FE) simulation was used to model the deformation of bimetallic laminates for various thickness reduction ratios, rolling temperatures, and tensile stresses. Particular attention was focused on the rolling pressure of Al and Cu layers in the simulation. The results show that the stress distribution in the bimetal Al/Cu laminates is an asymmetrical distribution. Moreover, the bonding strength of samples was obtained using the peeling test. Also, the fracture surface of roll bonded samples around the interface of laminates after the tensile test was studied to investigate the bonding quality by scanning electron microscopy (SEM).

Bifurcation in deformation behavior of Cu and Ta by accumulative roll-bonding at high temperature

Cu and Ta are co-deformed at 673K by the accumulative roll-bonding technique up to 8 passes. At an equivalent von Mises strain (ɛvm) of ~2 the deformation is bifurcated into shear accommodated by the ‘soft’ Cu, and plane-strain by the ‘hard-but-ductile’ Ta. This is attributed to transitions occurring collectively at ɛvm ~2 in crystallographic texture, partitioning of recovery and recrystallization, and the nature of interfaces as elucidated by orientation relations, Hall-Petch behavior and manifestation of instabilities at higher strain.

Investigation of Bonding Behavior of AA1050/AA5083 Bimetallic Laminates by Roll Bonding Technique

In this study, 1-mm AA1050/AA5083 bimetallic laminates were produced using roll bonding (RB) process. The RB process was carried out with thickness reduction ratios of 25, 50 and 75%, separately. Finite element simulation was used to model the deformation of bimetallic laminates for various experimental conditions. Particular attention was focused on the bonding of the interface between AA1050 and AA5083 layers in the simulation. The optimization of thickness reduction ratios was obtained for improvement of the bond strength of bimetallic laminates during RB process. During the simulation, the mean equivalent strain at the interface zone between the layers was found to reach the maximum value with a high quality bond for the sample produced with 75% of thickness reduction. Moreover, the fracture surface of samples around the interface of laminates after the tensile test was studied to investigate the bonding quality by scanning electron microscopy.

Electrochemical Evaluation of Lead Base Composite Anodes Fabricated by Accumulative Roll Bonding Technique

Accumulative roll bonding is used for the first time in lead systems to fabricate advanced lead base composite anodes. For this purpose, Ag as the most common and effective additive, Co as the best metallic immiscible substitution for Ag, and MnO2 as the ceramic and electrocatalytic agent have been used as additives to produce anodes. The accumulative roll bonding processed sheets have been fabricated under determined conditions. The electrochemical properties of the prepared samples are investigated by Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, Polarization tests, electrowinning tests, and Scanning Electron Microscopy. The results indicate that the ARB-processed composite lead sheets can be perfectly used as novel developed anodes. The advantages include 5.51 times increase of current density, in the Pb-pct0.5Ag 9-pass sample compared to pure lead anode, decreased charge transfer resistance from 56.31 (Ω cm2) in pure lead anode to 17.5 (Ω cm2) in the Pb-pct2MnO2 8-pass sample (72 pct lower), and decreased oxygen evolution potential from 1.95 (V/SHE) in pure lead anode to 1.77 (V/SHE) in the Pb-pct2MnO2 8-pass sample (0.18 (V/SHE) lower). Electrowinning tests results reveal Pb-2 pctMnO2 8-pass showed best anodic performance withsignificant lower compared corrosion rate (75 pct), product and electrolyte contamination, slime formation, energy consumption and higher Zn deposit and energy conservation (to 294 kWh/t-Zn). Finest Zn deposit morphology (effective reduced grain size corresponding to smoothness and compaction) has been supplied by Pb-2 pctMnO2 8-pass sample resulted from enhanced growth rate of Zn in lack of Pb contaminations that could act as suitable nucleation sites.

Emergence of stable interfaces under extreme plastic deformation

Atomically ordered bimetal interfaces typically develop in near-equilibrium epitaxial growth (bottom-up processing) of nanolayered composite films and have been considered responsible for a number of intriguing material properties. Here, we discover that interfaces of such atomic level order can also emerge ubiquitously in large-scale layered nanocomposites fabricated by extreme strain (top down) processing. This is a counterintuitive result, which we propose occurs because extreme plastic straining creates new interfaces separated by single crystal layers of nanometer thickness. On this basis, with atomic-scale modeling and crystal plasticity theory, we prove that the preferred bimetal interface arising from extreme strains corresponds to a unique stable state, which can be predicted by two controlling stability conditions. As another testament to its stability, we provide experimental evidence showing that this interface maintains its integrity in further straining (strains > 12), elevated temperatures (> 0.45 Tm of a constituent), and irradiation (light ion). These results open a new frontier in the fabrication of stable nanomaterials with severe plastic deformation techniques.

Mechanical Property and Fracture Behavior of Al/Mg Composite Produced by Accumulative Roll Bonding Technique

The Al/Mg laminated composite was fabricated by an accumulative roll bonding (ARB) technique using Al-1100 and Mg-AZ31 at 573 K. Tensile properties along rolling direction under different ARB cycles were evaluated at the ambient temperature. The tensile strength of the Al/Mg composite increased gradually till three ARB cycle and then decreased after the fourth ARB cycles. Scanning electron microscopy (SEM) was used to investigate the microstructure evolution and the failure mechanism. The Al/Mg interface with interface angles between 30° and 35° has minimum tensile strength. A higher or lower interface angle improves the tensile strength, and the interface angle can be reduced by increasing the number of cycles in the ARB process. Thus, the crack at the coarse intermetallic compounds and rupture of the Al layer after fourth cycle caused the premature failure of the specimens during the tensile test.

Titanium for Non-Aerospace Applications

The titanium industry has been on quite a ride over the past 5 years. In 2007, a boom in sponge and primary metal production capacity was fueled by the prospects of continued strong economic growth. Airframe production and global industrial expansion drove this recovery and growth after the very hard post-9/11 years. Then the global economic crisis hit in 2008 with its well-known effects on most every industrial sector. The titanium industry was particularly rocked by this crisis as the timing coincided with delays in the introduction of new airframe programs that had been eagerly anticipated for some time. These new products promised to revolutionize the industry that is so key to titanium producer’s businesses. Unfortunately, the downturn hit at just the time a large amount of new sponge capacity was due to come on line. Orders, deliveries, and inventories went into a slide. Even with a worldwide recovery still on shaky ground, the huge spike in airframe production, both legacy and new design, has turned things around in a hurry. Significantly, major industrial construction projects are also helping to add to the bright times ahead for titanium. In this issue, we take a look at areas other than the traditional aerospace applications that could provide major markets in the future to help add new dimensions and depth to the world titanium story. Everyone can agree that if titanium is going to reach its potential in the future, it will be because innovative processing in both primary metal production and product development drive a major reduction in the final cost of useful articles. Thankfully, while the worldwide titanium business has been restive at best over the last few years, researchers have been hard at work around the globe looking at the entire titanium value chain and working constantly toward the goals that have seemed to be so close yet so far away for decades. The articles that follow provide a glimpse of how innovative thinking in diverse areas like steelmaking, biomaterials, and transportation/industrial use might be used in innovative ways. Sachdev et al. present a well-developed overview of past and present use of titanium in automotive applications, and they trace the processing routes both current and emerging that could be used to meet the cost challenges that restrict the use of the metal in that market. This article is significant in that it not only details the places that titanium has been successful in automobiles in the past, but also it examines the use of new routes to break down barriers that currently exist to high-volume use of titanium. Peter et al. report on the development of titanium sheet processing from powder precursors. The article shows how the use of roll compaction and various postprocessing routes holds the potential for making affordable titanium sheet that could potentially enter the industrial and transportation markets in high volumes. Affordable powder processing has long been known as a viable route to making titanium products, and this report shows that a pathway exists to making mill products meeting commercial material specifications. Cojocaru et al. show that ultra-fine microstructures and strong texture intensities can be produced in Ti-25Ta-25Nb alloy using an accumulative rollbonding technique with stacked sheets. This severe plastic deformation process, combined with other thermo-mechanical treatments, can produce materials with high anisotropy for use in biomedical implant applications. Ferrotitanium is an important deoxidizing and alloying addition to modern micro-alloyed steels that are key to reducing vehicle weight in steel body and suspension structures. Jayashree Mohanty from the Raman College of Engineering reports on experiments carried out to validate the production of ferrotitanium using electrolytic reduction processing directly from titania slag. On a final personal note, this will be the last issue of JOM for which I will act as the advisor to the JOM, Vol. 64, No. 5, 2012

Microstructural Characteristics of Accumulative Roll-Bonded Ni-Al-Based Metal-Intermetallic Laminate Composite

The present investigation is an attempt to develop metal-intermetallic laminate composites based on Ni-Al system. In this study, Ni sheets and Al foils have been used for the development of Ni-Al laminate using accumulative roll-bonding technique at 773 K. The laminate composites were then subjected to the controlled annealing to affect reactive diffusion at the Ni/Al interface leading to intermetallic compound formation. The accumulative roll-bonded laminates showed good bonding of layers. Annealing treatment at 773 K led to formation of reaction product and maintained the interface integrity. A qualitative compositional analysis at the interfaces reflected the formation of Al-Ni compounds, and a gradual compositional gradient also across the interface. This process seems to be of promise so far as the continuous production of large scale metal-intermetallic laminate composites is concerned.

Interface Effects on the Quasi-Static and Impact Toughness of Discontinuously Reinforced Aluminum Laminates

Trilayer laminates consisting of two layers of aluminum alloy 7093 surrounding one layer of 7093/SiC/15p were produced via two roll-bonding techniques as well as by adhesive bonding. The effects of systematic changes in interface characteristics (i.e., weak bond via roll bonding with a thin ductile interlayer material, stronger bond via roll bonding without a thin ductile interlayer, and strongest bond via adhesive bonding with a semibrittle material) on the subsequent laminate toughness was studied. The fracture resistance of the laminates and the constituent materials was examined via instrumented Charpy notched impact testing in the crack-arrester orientation as well as by fracture-toughness testing of bend bars tested in the crack-divider and the crack-arrester orientations. The notched impact resistance of the trilayer crack-arrester laminates was found to be greater than both monolithic 7093/SiC/15p and 7093 samples of similar global thickness. The laminated structure promoted crack arrest, deflection, and large-scale deformation of the unreinforced layers, producing R-curve behavior. The tendency for interface delamination was predicted and confirmed based on recent mechanics-based analyses. The trilayer laminate structures tested in the crack-divider orientation exhibited a greater R-curve than either of the 7093/SiC/15p or 7093 samples tested at similar global thickness. Both types of roll-bonded laminates (i.e., stronger interface and weak interface containing a thin metal interlayer) exhibited a greater enhancement in Charpy impact toughness and mode I fracture toughness than did the adhesively bonded (i.e., semibrittle interface) laminates. These relative improvements in toughness were rationalized by estimating the contributions to energy absorption by the delamination and crack bridging in these systems and by the effects of the interface type on these processes. These results are generally relevant to the performance of these materials under impact and under certain blast loading and penetration situations.

Processing Ti-Al-Nb Composite Sheet Materials Using Cold Roll Bonding and Reaction Annealing

Multi-layered composite sheet materials with nominal composition of Ti-46Al-9Nb (at.%) were successfully processed from Ti, Al and Nb elemental foils using the cold roll bonding technique. To promote the formation of intermetallic compounds in these composites, annealing at 600°C was employed for specimens subjected to various amounts of reduction. The microstructures and phases that formed after cold rolling, the first annealing stage, and the second annealing stage were characterized using scanning electron microscopy (SEM) equipped with an energy dispersive x-ray spectrometer (EDS), transmission electron microscopy (TEM), and x-ray diffraction (XRD). Good bonding was achieved for all rolled samples with a threshold reduction in thickness of about 35% in the first rolling pass. No new phases were formed in the cold rolling stage. Annealing stage did promote the formation of the TiAl3 and NbAl3 phases at the interfaces.

Thermal performance of automotive aluminium plate radiator

The thermal performance of an automotive radiator plays an important role in the performance of an automobile’s cooling system and all other associated systems. For a number of years, this component has suffered from little attention with very little changing in its manufacturing cost, operation and geometry. As opposed to the old tubular heat exchanger configurations used in automotive radiators, plate heat exchangers currently form the backbone of today’s process industry with their advanced performance reaching levels the designers of tubular heat exchangers can only dream of. The aluminium roll-bonding technique widely used in manufacturing the cooling compartments for domestic refrigeration units is one of the cheapest methods for heat exchanger manufacturing. Using this technique, it is possible to manufacture a wide range of heat exchanger configurations that can help augment heat transfer whilst reducing pressure drops. CFD results obtained for a patterned plate heat exchanger using the CFD code FLUENT show tremendous levels of possible performance improvement on both sides of the heat exchanger. For the internal flow, heat transfer augmentation caused by the repetitive impingement against the dimple obstructions renders such geometries equal to those of aerospace industry pin-fins whilst lowering pressure drops due to the wider cross-sectional areas. For the external flows, the wider and wavy nature of the surface area increases heat transfer leaving the addition of extra surface roughness add-ons as an option.