5/5/2023 0 Comments Multipass propRecently, one SPD, called caliber rolling, showed advantages for mass production of bulk materials with an ultra-fine grain (UFG) in not only traditional steel but also non-ferrous metals (i.e., Al, Mg alloys). So, the driving force of this study is to develop a new approach to fabricating bulk pure Al with high strength. Although the above-mentioned SPD technologies can greatly improve the mechanical properties of pure Al, it also presents some disadvantages, such as complicated operation, harsh experimental conditions with high costs, and unsuitable for large-scale production in actual. , 8 passes of equal channel angular pressing (ECAP) remarkably refined the grain size of pure Al sheet below 500 nm with about 80% HAGBs, which also showed a high hardness value of 58 Hv. used high-pressure torsion (HPT) technology to decrease grain size and increase the misorientation to form HAGBs of pure Al, when the temperature and the equivalent strain were 773 K and 99, the grain size decreased to about 1 μm and the maximum hardness increased to 54 Hv, respectively. Due to the cost and operability of the experiment, it is not applicable in mass production. investigated extruded pure Al under low temperature using liquid nitrogen, the grain size can be reduced to 400 nm, and the TYS under this circumstance was increased to 168 MPa (or 56 Hv). studied the accumulative roll bonding (ARB) of pure Al and obtained TYS of 114 MPa after 6 passes, the enhanced mechanical property resulted from the synergy effect of both grain boundary strengthening and dislocation strengthening. The RS was presented to lead to a significant decrease in grain size and introduced about 70% Low-angle grain boundaries (LAGBs). explored the rotary swaging (RS) deformation of pure Al and found that when the true strain was 3, the tensile yield strength (TYS), and ultimate tensile strength (UTS) are 8 and 2 times that of the non-deformed sample, respectively. Thus, the control of grain boundary (GB) seems one of the effective methods for developing materials with excellent mechanical properties. As the deformation progresses, the dislocation density increases and it gradually evolves into the high-angle grain boundaries (HAGBs). After SPD, continuous dynamic recrystallization (CDRX) occurs, resulting in a mosaic-like structure or a cell block construction retarded by a dislocation wall. The grain size of UFGed material can reach even the nanometer level, which in turn, fine-grain strengthening can be obtained. Usually, the SPD refers to applying a large plastic strain at a certain temperature, changing the microstructure of the material to improve its mechanical properties, and finally obtaining an ultrafine-grained (UFGed) microstructure. To meet the increasing toughness requirements of structural materials, severe plastic deformation (SPD) technology is introduced to greatly improve the strength of materials. Aluminum (Al) and its alloys are widely used due to their high strength, good formability, and corrosion resistance. Nowadays, the researchers in automotive and aerospace fields are eager to develop high-performance structural metals, in which lightweight alloys become an important choice for such applications. The highest tensile yield strength (TYS), ultimate tensile strength (UTS) and elongation (El.) of caliber rolled pure Al (116 MPa, 135 MPa, and 17%, respectively) can be achieved after 13 rolling passes, which mainly attributed to grain refinement. Moreover, the initial cubic texture rotated to the brass component and finally changed to a mixture of Cube and Brass types. The dislocation density increased and it gradually evolved into the high-angle grain boundaries (HAGBs). In addition, due to the dynamic recrystallization (DRX), the average grain size reduced from 1 mm to 14 µm with the increase in rolling passes. As the number of rolling passes increased, the overall temperature, effective stress, and strain gradually increased, while the maximum rolling force decreased. The finite element modeling (FEM) simulation was performed to explore the changes in rolling force, effective stress and strain, and temperature under various rolling passes. The paper presents the microstructure and mechanical property of pure aluminum (Al) fabricated by multi-pass caliber rolling at room temperature.
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