Papers by Keyword: Accumulative Roll Bonding (ARB)

Abstract: Lamellar bands are the primary structural features in accumulative roll bonding (ARB) of sheet metals. The structural refinement in ARB sheets occur by forming a dense distribution of lamellar band boundaries. The lamellar band boundaries initiate as low angle interfaces, parallel to the existing lamellar band boundaries, irrespective of the crystallographic orientations of the parent lamellar bands. From an extensive investigation it was found that the transverse directions across the lamellar band boundaries are rotated by an angle equal to their misorientations. Such a phenomenon is not sustained when the boundaries turn to high angle.

Abstract: An Ultrafine grain (UFG) microstructure is developed on the sheet of Al-2.4wt%Cu-0.3wt%Si alloy after three passes of accumulative roll bonding (ARB) process. The detailed of the microstructural features and phases at different strain condition has been studied by transmission electron microscopy (TEM). Observation indicates at the possibility of dynamic recovery and recrystallisation during the ARB processing itself. The material becomes ultrafine grains after three passes of ARB itself with the formation of dynamically recrystallised grains all over the sample. TEM evidence is presented in support of this proposal.

Abstract: In this paper, accumulative roll bonding (ARB) has been used to prepare the Al/Mg alloy multilayer structure composite materials with 1060Al sheet and MB2 sheet. The evolution of microstructure of the cladding materials during ARB processes was observed by optical microscope, scanning electron microscopy, and micro-hardness was measured by micro-hardness tester. The results show that a multilayer structure material of Al/Mg alloy with excellent bonding characteristics and fine grained microstructure was prepared by ARB processes. With the ARB cycles increasing, Mg alloy layer in multilayer composite material was necked and fractured, and the hardness of the Al and Mg alloy was increased. Average grain size was less than 1μm after ARB4 cycles.

Abstract: Microstructural evolution of a copper alloy processed by accumulative roll-bonding (ARB) was investigated by EBSD analysis. The grains became thinner and elongated to the rolling direction with increasing the number of ARB cycles. The subdivision of the grains to the rolling direction actively begins to occur after 5 cycles of the ARB, resulting in formation of ultrafine grains with small aspect ratio. After 8 cycles, the ultrafine grained structure with the average grain diameter of 250nm developed in almost whole regions of the sample. In addition, the fraction of high-angle grain boundaries increased with the number of ARB cycles and reached about 0.7 after 8 cycles. The texture development of the ARB processed samples was different depending on the number of ARB cycles and the positions in the thickness.

Abstract: Usually the heat treatment in the cyclic ARB passes is indispensable to reduce work-hardening effects and improve interface bonding quality. The possibility of accelerating grain refinement of aluminum sheets with a dimension of 300 mm×50 mm×1 mm is investigated during the ARB process at room temperature, in which the samples are rotated by 180 degree around normal plane axis perpendicular to the rolling plane between the adjacent cycles. By means of optical microscopy and transmission electron microscopy, it shows that the bonding interfaces can not obviously observed after five cycles, and grains are refined to be ~0.5 μm. Tensile tests show the ARB samples exhibit strain hardening behavior after yielding without a sudden fracture even up to seven cycles of ARB. The softening behavior and enhanced ductility was explained by dynamic recovery, the recrystallization process and even abnormal large grains.

Abstract: With the increase of interest in using ultra-fine and nano-grained metals for structural purposes, the need to build on the knowledge pool regarding the response and behaviour of those metals under a mechanical load becomes more vital. However, it is well known that, especially for this type of materials such as the ECAPed and ARBed materials, the thermo-mechanical history affects the mechanical behaviour of the product strongly. Although ECAP and ARB are different techniques under the category of severe plastic deformation, similarities in their cyclic deformation response is observed from time to time. Specifically, the microstructural mechanisms involved in accommodating cyclic plastic strain in these two types of materials is seemingly comparable. The similarities arise from the similar microstructures in the majority of the volume of the bulk. In this report, the cyclic deformation response, and the related microstructural mechanisms of ECAPed copper will be discussed first and those of ARBed second. A comparison between ECAPed copper and ARBed copper will then be performed. Furthermore, the differences due to the unique features of ARBed material will be discussed. Lastly, the reasons behind the observed similarities in cyclic deformation behaviour and the related micro-mechanisms for metals process with the two different techniques will also be explored.

Abstract: Sliding wear behavior of severely deformed 6061 aluminum alloy sheets by accumulative roll bonding (ARB) process subjected to dry sliding wear at different loading and sliding velocities was investigated using a pin on disc wear machine. The sheets were processed up to five ARB cycles in order to induce a high strain (~ 4.0) to the samples. EBSD results showed that after five cycles of ARB, sheets were found to contain ultra-fine grains with high fraction of high angle grain boundaries. Wear was continuously monitored by measuring the weight losses and morphologies of worn surfaces by scanning electron microscope (SEM), and a model for the wear of the ARB-processed samples was proposed.

Abstract: Various different severe plastic deformation processes (SPD) have been developed to produce ultra-fine grained (UFG) materials during the last two decades. One very important material property that the UFG materials should have for structural materials application is good wear resistance. This review paper presents some recent work related to the wear resistance of materials processed by SPD, in particular for alloys processed by using equal-channel angular pressing (ECAP) and accumulative roll-bonding (ARB).

Abstract: Dispersed nanoparticles are introduced from stabilized suspensions during the accumulative roll bonding process in aluminium AA1050A by air gun spraying up to a final volume fraction of 0.1 % after eight cycles. Additional strengthening caused by particle insertion is observed and strongly depends on the suspension medium and stabilizing agent as both influence interfacial bonding of the particles to the matrix. The particle insertion furthermore results in reduced peel strength of the sheets irrespective of particle material and size caused by a reduction of effective metal to metal bonding area during rolling through the presence of the particles.

Abstract: In the present research, the microstructural features of ultrafine grained Cu-30 Zn alloy via ARB at room temperature were investigated by X-ray diffraction peak profile analysis. The character of dislocations was determined by analyzing the dislocation contrast factors. The average contrast factors for the different reflections obtained by determination of the type of dislocations and Burgers vectors in crystals. Also, using the modified Williamson–Hall and Warren–Averbach procedure size parameters, the effective outer cut-off radius and density of dislocations were determined. Assuming that the grain size distribution is log-normal, the median and the variance of the size distribution of sub grains were obtained. It was found that the crystallite size is reduced substantially, while the dislocation density increases up to 2 cycles of ARB. After 2nd cycle, dislocation density decreases. This is attributed to the occurrence of dynamic restoration process which takes place during next ARB cycles.