Research on Grain Refinement Mechanism of 6061 Aluminum Alloy Processed by Combined SPD Methods of ECAP and MAC

Abstract

Equal channel angular pressing (ECAP) and multi-axial compression deformation (MAC) are severe plastic deformation (SPD) processes that produce bulk nanostructured materials with ultrafine grains. The grains could be observably refined by multi-pass of ECAP and MAC. This research proposed new routes of cyclic equal channel compression (CECC), which combines ECAP and MAC to increase the mechanical properties of 6061 aluminum alloy. The tests, which are conducted through electron backscattered diffraction (EBSD) and transmission electron microscope (TEM), were performed on the grain size, recrystallization distribution, misorientation distributions, dislocations, and secondary phase distributions of CECC-processed 6061 aluminum alloys on the purpose of exploring the mechanism of grain refinement. MEM is the short form for the CECC processing route of MAC + ECAP + MAC, which is one ECAP pass between two MAC passes. The tests results showed that the average grain size could reach to as much as 1.1 μm after two MEM deformation circles named MEM-MEM, with the non-annealing average grain size being 21 μm and recrystallization annealed average grain size being 28 μm. The dislocation cells, which could be transformed into sub-grains with the increase of the strain, were formed by the slip and the accumulation of dislocations. The secondary phase was Mg2Si, which could prevent the refined grains from growing up again by pinning at the grain boundaries. Above all, the dislocation proliferation and secondary phases will both lead to the grain refinement.

Advances in surface modification of tantalum and porous tantalum for rapid osseointegration: A thematic review

“…One of these is severe plastic deformation (SPD), a technical method to prepare ultra-fine grain (<1 μm) materials by introducing large strain variables in the process of deformation. Compared with the conventional plastic deformation method, the SPD mostly produces larger deformation through strain accumulation, which can effectively refine the metal and obtain sub-micron or even nanometer-scale grains ( Zhang et al, 2018 ). Accumulative roll bonding (ARB), high-pressure torsion (HPT), and equal channel angular pressing (ECAP) are common SPD technologies.…”

Effect of Al-5Ti-0.25C-0.25B and Al-5Ti-1B Master Alloys on the Microstructure and Mechanical Properties of Al-9.5Si-1.5Cu-0.8Mn-0.6Mg Alloy

“…Amongst the cast aluminum alloys, in a variety of situations, Al-Si alloys find widespread usages, such as the production of automotive engine pistons, cylinder blocks, car chassis, wheels, and other components [ 1 , 2 , 3 , 4 , 5 , 6 ]. The Al-9.5Si-5Cu-0.8Mn-0.6Mg alloy is obtained by melting and casting before extrusion, during which time problems such as the segregation of alloy elements, developed dendrites, and coarse brittleness often occur, giving rise to a decrease in the alloy’s mechanical properties [ 7 ]. According to the grain refinement view, the Sr modification of eutectic silicon can optimize the alloy properties and improve its machinability and serviceability.…”

The Influence of the Proportions of Titanium and Boron in the Al and AlSi7-Based Master Alloy on the Microstructure and Mechanical Properties of Hypoeutectic Silumin, AlSi7Mg

“…The process of the chemical modification of hypoeutectic silumins was described in 1921 [41]. Since then, a lot of works have been written showing the influence of various elements, chemical compounds [42][43][44][45] and the technological processes [46][47][48][49][50][51][52][53][54][55][56][57] on the microstructure and mechanical properties of the tested silumins. Unfortunately, despite such a significant amount of research, it has not been possible to clearly identify the mechanisms causing microstructure refinement and increases in mechanical properties.…”