Accumulative Roll Bonding Cycles Research Articles

Fabrication of Al–2 vol% Al2O3/SiC hybrid composite via accumulative roll bonding (ARB): An investigation of the microstructure and mechanical properties

An Al/Al2O3/SiC hybrid metal matrix composite was fabricated by accumulative roll bonding (ARB). A mixture of Al2O3 and SiC (2vol%) powders was poured between four Al layers during the first two ARB cycles. The process was continued up to eight cycles without adding the powders in subsequent cycles. For comparison, non-reinforced (monolithic) Al was also processed by ARB under the same conditions. At the initial stages, particle free zones as well as particle clusters were observed on the microstructure of the composite. After eight ARB cycles, a composite with a uniform distribution of particles was produced. At this stage, the tensile strength of the hybrid composite and the monolithic Al reaches to about 195MPa and 150MPa, respectively, about 5.3 and 4 times larger than that of annealed Al. The hardness of the composite and the monolithic Al was measured as 83 and 58 VHN, respectively. Fracture surface after tensile testing revealed dimples at some regions after eight ARB cycles.

Comparison of microparticles and nanoparticles effects on deformation texture of steel-based composite and nanocomposite fabricated by the ARB process

In this study, the effect of SiC microparticles and nanoparticles on deformation texture of steel-based composite and nanocomposite fabricated by the accumulative roll bonding (ARB) process was investigated. Textural evolution during the ARB process was evaluated using X-ray diffraction. It was found that the presence of microparticles and nanoparticles in the IF steel matrix changed the intensity of texture components and fibers. There was a texture transition from rolling texture to shear one for pure IF steel, steel-based composite, and steel-based nanocomposite. However, the texture transition occurred in different cycles for these samples. It was realized that recrystallization occurred in pure IF steel, steel-based composite, and steel-based nanocomposite after the third, second, and first ARB cycles, respectively. In addition, occurrence of recrystallization in the steel-based composite and nanocomposite was sooner than in pure IF steel. Finally, it was found that with increasing the number of cycles, the fraction of low misorientation angle grain boundaries decreased and the fraction of high misorientation angle grain boundaries increased.

Effect of stacking fault energy on mechanical properties of nanostructured FCC materials processed by the ARB process

In the present work, the effect of stacking fault energy on the mechanical properties of aluminum, copper, and brass fabricated via the accumulative roll bonding (ARB) process was investigated. Mechanical properties and microstructural evaluation of the samples were evaluated by tensile and hardness tests and also transmission electron microscopy (TEM). It was found that differences in the mechanical properties during the ARB process of aluminum, copper, and brass were completely related to their stacking fault energies (SFEs). The tensile strength of the brass was much higher than that of the copper and aluminum at all ARB cycles. This was attributed to smaller grain size, higher dislocation density and higher twin density of the brass during the ARB process. It was realized that the ductility of the brass was higher than that of the copper for all ARB cycles. This was related to higher twin density in the brass sample. The hardness results were indicated that the saturation of dislocation density that occurred at the second, third, and fifth cycles for aluminum, copper, and brass, respectively. In fact, when the SFE was decreased, the number of ARB cycles for saturation of hardness increased.

Wear behavior of nanostructured Al/Al2O3 composite fabricated via accumulative roll bonding (ARB) process

In the present work, wear behavior of nanostructured aluminum and composite performed by accumulative roll bonding (ARB) process was investigated. The wear characteristics were studied by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Also, transmission electron microscopy (TEM) and crystallographic texture investigations were performed. The results indicated that the ARB process led to the decrease in wear resistance of the monolithic and composite samples compared with as-received aluminum strip. The adhesive, abrasive and delaminating wear mechanisms occurred in the monolithic and composite samples simultaneously. At higher number of ARB cycles, delamination was the dominant wear mechanism. It was found that the surface damage of the composite was more extensive than that of the monolithic sample due to the occurrence of spalling mechanism. It was suggested that the intense Rotated Cube {001}〈110〉 texture component of composite helped to crack nucleation and propagation greatly. The role of delamination and especially, spalling in decreasing the wear resistance of composite was very important such that it eliminated the role of reinforcing particles and grain size on the wear resistance.

An alternative method for manufacturing high-strength CP Ti–SiC composites by accumulative roll bonding process

For the first time, the accumulative roll bonding (ARB) process was used as an effective alternative method for manufacturing Ti–SiC composites and compared with the monolithic ARBed Ti. High-strength monolithic commercially pure titanium (CP Ti) and CP Ti–SiC composites with effective uniform reinforcement distribution were fabricated by this process. The tensile test, Vickers hardness measurements and SEM observations were done for the characterization of materials. A significant increase in yield and tensile strength and a drastic decrease in elongation were observed by applying 8cycles of ARB process. An unexpectedly slight decrease of yield and tensile strength along with elongation was observed after the sixth ARB cycle for the monolithic sample. It was attributed to the weakening of the bond between the titanium layers in the final cycles. Strength of the composite samples was higher than that of the monolithic sample and did not decrease in the final ARB cycles. This was caused by the significantly improved distribution of SiC particles in the titanium matrix.

Hybrid composites produced by anodizing and accumulative roll bonding (ARB) processes

In this study, microstructure and mechanical properties of Al/1.6vol% Al2O3/1.5vol% B4C hybrid composite produced by anodizing and accumulative roll bonding (ARB) processes were investigated. Microstructural observations and fractography were performed by scanning electron microscopy (SEM). Also, the mechanical properties were investigated by tensile and microhardness tests. It was found that with increasing the number of ARB cycles, a better distribution of Al2O3 and B4C particles was obtained in the aluminum matrix. The hybrid composite after the tenth cycle demonstrated a uniform distribution and a strong bonding between the particles and the matrix without any porosity. Furthermore, ARB-processed monolithic and also, the hybrid composite showed much higher tensile strength than the annealed aluminum sample. In addition, elongation of ARB-processed monolithic and also, the hybrid composite was decreased in the first step and then increased as a result of increasing the number of cycles. Moreover, the ARB-processed monolithic and the hybrid composite exhibited higher hardness than the annealed aluminum. Finally, it was realized that the monolithic and hybrid composite samples had a shear ductile fracture, dimples and shear zones. However, the number of sources in the void nucleation of the composite was more than that of the monolithic sample.

Fabrication of nanostructured Al/Cu/Mn metallic multilayer composites by accumulative roll bonding process and investigation of their mechanical properties

Multilayered Al/Cu/Mn composites were produced from aluminum 1100 strips, commercial copper foils and manganese powders, through accumulative roll bonding (ARB). The structural and microstructural evolution of the produced composites was studied by X-ray diffraction and scanning electron microscopy. Also, their mechanical properties at various ARB cycles were studied by microhardness and tensile tests. In this process after nine ARB cycles, a multilayered Al/Cu/Mn composite with homogeneously distributed, fragmented copper layers and Mn powders in the aluminum matrix was produced. Also, it was observed that with increasing strain by progression of the ARB process, the strength and microhardness of the produced composites increased.

Comparison of microparticles and nanoparticles effects on the microstructure and mechanical properties of steel-based composite and nanocomposite fabricated via accumulative roll bonding process

In the present work, a comparison of microparticles and nanoparticles effects on the microstructure and mechanical properties of steel-based composite and nanocomposite fabricated via accumulative roll bonding (ARB) process was studied. The microstructure of the fabricated composite and nanocomposite after fourth cycle of the ARB process exhibited an excellent distribution of SiC micro/nano particles in the IF steel matrix without any porosity. Unlike the nanocomposite, the particle breaking (cracking) was one of the most important phenomena that occurred during ARB process of composite. The findings revealed that with increasing the number of ARB cycles, the tensile strength of the ARB-processed composite and especially nanocomposite improved, but their elongation decreased at first step and then increased at second step. In addition, the ARB-processed composite and especially nanocomposite exhibited a higher hardness than the annealed IF steel so that the hardness values of the composite and nanocomposite were 4.18 and 4.44 times higher than that of the annealed IF steel, respectively.

Microstructure evolution and mechanical properties of Cu/Zn multilayer processed by accumulative roll bonding (ARB)

Cu/Zn multilayer was processed by accumulative roll bonding (ARB) up to eight cycles. The evolution of microstructure and its correlation with mechanical properties was investigated. Necking and rupture of constituents were observed at intermediate cycles. The intermetallic CuZn5, microcracks and Kirkendall porosities were formed during ARB. After eight ARB cycles, a laminated composite with wavy interfaces and lenticular fragments of Cu was produced. The maximum tensile strength was achieved after four cycles, which was about 1.4 times higher than that of pure Cu. The hardness of individual layers increased continually with increasing the ARB cycle. Tensile fracture surfaces reveal dimples in both Cu and Zn at early ARB cycles.

Flow stress analysis of ultrafine grained AA 1050 by plane strain compression test

Plane strain compression (PSC) test was used to study the flow stress of ultrafine grained commercially pure aluminum at large strains. AA 1050 sheets were processed by various Accumulative Roll-Bonding (ARB) cycles up to 10 cycles as the initial specimens for the test. An approach was developed to measure the coefficient of friction and to suppress its effect on the results. It is shown that as a result of having an anisotropy parameter (R-value) of less than one, Von-Mises tensile strengths are significantly higher than PSC strengths. Comparing these strengths, the R-value as an average anisotropy parameter of rolling and transverse directions is estimated for the ARBed sheets, where it is decreased by 6 ARB cycles and increased by the following 8–10 cycles. Estimated R-values are used for drawing the flow curves based on the Hill's 1948 anisotropic plasticity. While the flow curves display a steady state flow stress for all samples, a flow softening is observed at the beginning of the curves for 8 and 10-cycle specimens up to strain of 0.3. It is revealed that despite evidence for shear banding, the softening has a microstructural reason due to different strain rates during pre-straining by ARB and PSC. In other words, since the grain refinement during ARB up to 8 and 10 cycles has exceeded the smallest possible grain size of the PSC test, post-ARB deformation of these two specimens result in a microstructural revolution toward the preferred steady state conditions along with a gradual work softening.

Manufacturing Al/steel multilayered composite by accumulative roll bonding and the effects of subsequent annealing on the microstructural and mechanical characteristics

In this research, multilayered Al/steel composites were produced by accumulative roll bonding (ARB) process using Al-1100 and St-12 sheets up to three cycles. Microstructure and mechanical properties of the Al/steel multilayered composite were studied during various ARB cycles by scanning electron microscopy (SEM), tensile and Vickers microhardness tests. It was observed that after the second ARB cycle, steel layers were necked and fractured and tensile properties decreased dramatically. For this reason, the effects of annealing temperature and time on the mechanical properties of composite were evaluated at the first cycle. The results indicated that generally, strength of Al/steel composite decreased and elongation increased after annealing. However, the strength between 300°C and 400°C is approximately constant. Additionally, the annealing treatment at 500°C dramatically reduced the strength due to the formation of a brittle intermetallic layer with high hardness at the Al/steel interface.

Effect of SiC nanoparticles on the mechanical properties of steel-based nanocomposite produced by accumulative roll bonding process

In the present work, the effect of SiC nanoparticles on the mechanical properties of steel-based nanocomposite produced by accumulative roll bonding (ARB) process was investigated. The microstructure of the fabricated nanocomposites after fourth ARB cycle was exhibited an excellent distribution of SiC nanoparticles in the interstitial free (IF) steel matrix without any porosity. The findings revealed that with increasing the number of ARB cycles, the tensile strength of the ARB-processed pure IF steel and also nanocomposites was improved, but their elongation was decreased at first step and then was increased at second step. The tensile strength of the ARB-processed pure IF steel and nanocomposites was 4.5 and 6times higher than the same value was obtained for annealed IF steel, respectively. In addition, the ARB-processed pure IF steel and nanocomposite was exhibited a higher hardness than the annealed IF steel so that the hardness values of the pure IF steel and nanocomposite were 3.78 and 4.44times higher than that of the annealed IF steel.

Fabrication of Al/Al2O3/TiC hybrid composite by anodizing and accumulative roll bonding processes and investigation of its microstructure and mechanical properties

In the present study, Al/Al2O3/TiC hybrid composite was produced using anodized strips and accumulative roll bonding (ARB) process. Alumina layers with various thicknesses were firstly obtained by anodizing the aluminum strips at different times. The anodized strips were then used along with certain amount of TiC particles (1vol%) as dispersed layer in order to fabricate Al/Al2O3/TiC hybrid composite. The resulting microstructures as well as the corresponding mechanical properties of the composites in different cycles of ARB process were studied. It was found that after one ARB cycle, departing and fracturing phenomena occurred in brittle alumina layer, followed by breaking down the alumina fragments to finer particles as the number of rolling cycles increased. In addition, by applying eight ARB cycles, the distribution of reinforcement particles (Al2O3, TiC) in aluminum matrix became highly uniform. It was shown that the mechanical properties of the hybrid composite such as tensile strength and elongation were enhanced as the number of ARB cycles increased. The results also showed that adding of up to 1.6vol% alumina in aluminum matrix enhanced considerably the yield and tensile strength of hybrid composite, whereas increasing the amount of alumina to 2.1vol% deteriorated the tensile properties. Finally, the fracture surfaces of the samples after the tensile tests showed that the fracture mode of composite was shear ductile rupture.

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.

Evaluation of microstructure and mechanical properties of Al/Al2O3/SiC hybrid composite fabricated by accumulative roll bonding process

In this investigation, a new kind of metal matrix composites with a matrix of pure aluminum and hybrid reinforcement of Al2O3 and SiC particles was fabricated for the first time by anodizing followed by eight cycles accumulative roll bonding (ARB). The resulting microstructures and the corresponding mechanical properties of composites within different stages of ARB process were studied. It was found that with increasing the ARB cycles, alumina layers were fractured, resulting in homogenous distribution of Al2O3 particles in the aluminum matrix. Also, the distribution of SiC particles was improved and the porosity between particles and the matrix was decreased. It was observed that the tensile strength of composites improved by increasing the ARB passes, i.e. the tensile strength of the Al/1.6vol.% Al2O3/1vol.% SiC composite was measured to be about 3.1times higher than as-received material. In addition, tensile strength of composites decreased by increasing volume fraction of SiC particles to more than 1vol.%. Scanning electron microscopy (SEM) observation of fractured surfaces showed that the failure mechanism of broken hybrid composite was shear ductile rupture.

Fabrication of nanoparticle strengthened IF steel via ARB process

Accumulative roll bonding (ARB) process was used in this study as a very effective method for fabrication of the nanoparticle strengthened IF steel. The microstructure of the produced composites after fourth cycle of the ARB process was exhibited a highly-uniform distribution of SiC nanoparticles in the IF steel matrix without any porosity. It was found that when the number of ARB cycles was increased, the tensile strength of the produced composites was improved, but their elongation was decreased at first step and then was increased at second step. The tensile strength of the composite was 6 times higher than that of the annealed IF steel. The findings also revealed that with increasing the number of cycles, first hardness rapidly increased and then dwindled.

Microstructure and Mechanical Properties of AA5005/AA6061 Laminated Composite Processed by Accumulative Roll Bonding

The AA5005/AA6061 laminated composite has been fabricated by the accumulative roll bonding (ARB) using commercial AA5005 and AA6061. In the ARB process, one piece of AA5005 sheet and one piece of AA6061 sheet were stacked together and rolled with a 50 pct reduction without any lubrication. The materials were heated at 473 K (200 °C) for 10 minutes before each rolling process and were deformed up to four cycles to accumulate an equivalent strain of 3.2 and form an AA5005/AA6061 laminated composite. Mechanical properties and microstructure of the laminated composites were tested. The hardness and tensile strength increased, and the grain size reduced with the number of ARB cycles. Ultrafine grains elongated along the rolling direction were developed during the ARB process. The thicknesses of the grains of both the AA5005 and AA6061 layers were less than 200 nm after the fourth cycle. The uniform elongation decreased drastically after the first cycle ARB and stayed almost unchanged after further ARB process. The hardness of the AA5005 layer was slightly lower than that of the AA6061 layer. The microstructures from optical microscope and transmission microscope showed that in the AA6061 layer large precipitates in the micron scale and small particles less than 100 nm were present, whereas in the AA5005 layer there were large scale precipitates, but no small-sized particles.

Accumulative roll bonding of multilayered Cu/Zn/Al: An evaluation of microstructure and mechanical properties

In the present study, multilayer Cu/Zn/Al was processed by accumulative roll bonding (ARB) up to 14 cycles. By using scanning electron microscopy and elemental mapping, necking and rupture of layers upon 4 and 5 cycles were detected. A uniform distribution of fragments was achieved after 14 cycles. The formation of intermetallic CuZn5 after 5 cycles was confirmed by X-ray diffraction. Microcracks were formed due to intermetallic formation at the interface and several cavities were observed in Zn layer. Results showed that the strength increased up to 290MPa after 4 cycles and dropped afterward. Microhardness measurement indicated that hardness of individual layers increased continually with increasing the ARB cycle. Tensile fracture mode for Cu and Al layers was ductile at initial cycles and then changed to brittle at higher cycles. The fracture mode for Zn layer was brittle at all stages.

Microstructural Evolution and Mechanical Property of AA5050 Alloy Deformed by Accumulative Roll Bonding

In this study, ultrafine-grained AA5050 sheets were fabricated by the accumulative roll bonding (ARB) process. Transmission electron microscope observations showed that at the early stage of ARB, the grain size was reduced in the normal direction and became elongated along the rolling direction. The elongated grains were cut out by dense dislocations, which then tangled and condensed, resulting in the formation of dislocation cells. As the deformation proceeded, the dislocation cells evolved to sub-grain boundaries and then grain boundaries. The ultrafine-grained microstructure was obtained via four ARB cycles. The tensile tests at 473 K and 523 K (200 °C and 250 °C) showed large elongations for strain rates of 1 × 103 s−1 and 1 × 104 s−1.

Abnormal Ductility Increase of Commercial Purity Al During Accumulative Roll Bonding

In this paper, sheets of commercial purity Al were fabricated by the accumulative roll-bonding (ARB) method up to six cycles. To increase the shear deformation, no lubricant was used during the ARB processing and the samples were carried out for ARB processing without any preheat treatment. One interesting finding is that the ductility and strength both increased during the first several cycles of ARB processing. It is proposed that the initial rolling texture might play an important part in the subsequent ARB processing since the original Al sheets for ARB processing have not been subjected to any annealing. The microstructures of the specimens after each ARB cycle were investigated by transmission electron microscopy and correlated with the mechanical properties.