Micro/Meso-Scale Equal Channel Angular Pressing of Al 1070 Alloy: Microstructure and Mechanical Properties

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JMEPEG https://doi.org/10.1007/s11665-020-05090-4

Micro/Meso-Scale Equal Channel Angular Pressing of Al 1070 Alloy: Microstructure and Mechanical Properties Walaa Abdel-Aziem, Atef Hamada, Takehiko Makino, and Mohsen A. Hassan (Submitted May 30, 2020; in revised form July 18, 2020) In the present study, Al 1070 alloy pins were processed via micro/meso-scale equal channel angular pressing (channel diameter 1.5 mm, the smallest channel diameter has ever been achieved in mesoscale), up to four passes at room temperature. The microstructure characteristics, i.e., grain size, and misorientation angle distributions were analyzed by high-resolution electron backscatter diffraction on the transverse plane for the ECAPed samples. Tensile properties for such small processed pins were measured by constructed micro/ meso-scale tensile machine. The gauge length and the gauge diameter were 2 mm and 1.5 mm, respectively. After the fourth ECAP pass, the results revealed that the microstructure was refined remarkably from 15.5 lm (the initial undeformed sample) to nearly 1.9 lm due to the gradual transformation of the lowangle grain boundaries into high-angle grain boundaries as a result of the occurrence of grain subdivision. Micro/meso-scale ECAP does a significant enhancement in the ultimate tensile strength by 63%, whereas the ductility decreased after the fourth ECAP pass by 47.3% and this is supposed to be ascribed to the continuous decrease in subgrain size. The above results prove that the ECAP process has the potential for obtaining fine grains and improving material tensile properties even in micro/meso-scale. Keywords

boundaries, characterization, EBSD, ECAP, microstructure, refinement, strength, subdivision

1. Introduction Recently, the ubiquitous trend toward microtechnology has been increased tremendously to meet the demand of microparts in various engineering applications such as biomedicals, consumer electronics, robotics and communication devices. Micro/meso-scale is one of the promising microtechnologies which deals with the product miniaturization with a small or microscopic scale to fabricate very small complex metallic parts through plastic deformation of materials. However, the theory of micro/mesoforming processes differs from those in the macroscale due to the occurrence of size effect (Ref 1-7). Thus, when the part is miniaturized in its geometric dimensions, some intrinsic dimensions of the deformed material including the grain size and the surface roughness cannot be scaled down with the geometric ones (Ref 2, 8-10). Such difference influences the materialÕs deformation behavior due to the decrease in the number of defects and/or the number of grains that can lead to failure probability during fabrication of microparts (Ref 2). Vollertsen et al. (Ref 7, 11, 12) and Geiger Walaa Abdel-Aziem, Department of Mechanical Design and Production Engineering, Faculty of Engineering, Zagazig University, P.O. Box 44519, Zagazig, Egypt; Atef Hamada, University of Oulu, Kerttu Saalasti Institute, Pajatie 5, 85500 Nivala,

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