Microstructural Evolution at Micro/Meso-Scale in an Ultrafine-Grained Pure Aluminum Processed by Equal-Channel Angular Pressing with Subsequent Annealing Treatment

Abstract

Micro-forming with ultrafine-grained (UFG) materials is a promising direction for the fabrication of micro-electro-mechanical systems (MEMS) components due to the improved formability, good surface quality, and excellent mechanical properties it provides. In this paper, micro-compression tests were performed using UFG pure aluminum processed by equal-channel angular pressing (ECAP) with subsequent annealing treatment. Microstructural evolution was investigated by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results show that microstructural evolutions during compression tests at the micro/meso-scale in UFG pure Al are absolutely different from the coarse-grained (CG) materials. A lot of low-angle grain boundaries (LAGBs) and recrystallized fine grains are formed inside of the original large grains in CG pure aluminum after micro-compression. By contrast, ultrafine grains are kept with few sub-grain boundaries inside the grains in UFG pure aluminum, which are similar to the original microstructure before micro-compression. The surface roughness and coordinated deformation ability can be significantly improved with UFG pure aluminum, which demonstrates that the UFG materials have a strong potential application in micro/meso-forming.

Effect of Grain Size on Formability and Deformation Mechanism of High‐Purity Aluminum during Micro‐Embossing Process at Elevated Temperature

“…Saotome et al investigated the effect of grain size on filling behavior during embossing process and found that the finer grain provided better filling ability. Similar phenomenon was also proved to be valid for the pure Al, pure Cu, pure Ni, and magnesium alloy . Thus, it was confirmed that grain size effect would influence the forming behavior during micro‐embossing and UFG‐grained materials were of better formability.…”

“…High purity (99.999%) aluminum was applied as an initial material. The equal‐channel angular pressing (ECAP) for pure Al was carried out at room temperature and the corresponding process parameters were provided by the previous research . After 8 ECAP passes, UFG pure Al with an average grain size of approximately 1 μm was obtained.…”

Preparation and Mechanical Behavior of Ultra-High Strength Low-Carbon Steel

“…The methods of severe plastic deformation (SPD) are an effective means of grain refinement [1][2][3][4], which have been widely used in the preparation of ultra-high strength materials. The SPD methods mainly include cold rolling [5,6], equal channel angular pressing (ECAP) [7][8][9], high-pressure torsion (HPT) straining [10,11], accumulative roll-bonding (ARB) [12][13][14], multidirectional forging (MDF) [15][16][17], etc. Valiev et al [18,19] reported the preparation and application of bulk nanostructured materials from SDP.…”

Innovative Applications of Ultrafine-Grained Materials

“…Meanwhile, there is an obvious transition from nonuniform deformation to uniform deformation after micro-compression testing with decreasing of grain size as shown in Figure 8a-e. The nonuniform deformation can be improved significantly, and the compressed specimens using UFG pure Al are cylindrical with a smooth surface as shown in Figure 8d and e [77,78]. Research on the micro-extrusion of UFG aluminum showed that the material flow became more uniform because more grains were deformed during micro-extrusion [79].…”