Abstract
SPD (several plastic deformations) methods make it possible to obtain an ultrafine-grained structure (UFG) in larger volumes of material and thus improve its mechanical properties. The presented work focuses on the structural and mechanical changes of aluminium alloy AlMgSi0.5 (EN AW 6060) during processing by repeated extrusion through the ECAP rectangular channel. After a four-pass extrusion, the samples’ microstructures were observed using an optical microscope, where refinement of the material grains was confirmed. Tensile tests determined the extrusion forces and allowed interpretation of the changes in the mechanical properties of the stressed alloy. The grain size was refined from 28.90 μm to 4.63 μm. A significant improvement in the strength of the material (by 45%) and a significant deterioration in ductility (to 60%) immediately after the first extrusion was confirmed. The third pass through the die appeared to be optimal for the chosen deformation path, while after the fourth pass, micro-cracks appeared, significantly reducing the strength of the material. Based on the measurement results, new analytical equations were formulated to predict the magnitude or intensity of the volumetric and shape deformations of the structural grain size and, in particular, the adequate increase in the strength and yield point of the material.
Highlights
In the range of grain sizes d−1/2 < 880 m−1/2, the values are consistent with relation (2), but at smaller grain sizes, the constant ky reached negative values. These results indicate a transition from hardening to softening of the material and an inverse Hall–Petch effect with much larger values than for the intermediate grain size transition
Aluminium alloy AlMgSi0.5 (EN AW 6060) is a medium-strength, heat-treatable alloy with a strength slightly below 6005 A
The first sample from each pair was used for metallographic examinations and the second for the determination of mechanical properties
Summary
The demand for more sophisticated materials is growing rapidly. one of the objects of current research in the field of advanced materials is the continuous improvement of their design to improve their physical, chemical, and mechanical properties leading to their use in high-end applications. Modifying the microstructure of a material is an effective method of tailoring its properties to achieve specific improvements in material properties In this paradigm, refining the grain size of crystalline materials to produce ultrafine-grained (UFG) or nanocrystalline (NC) materials has been shown to be an effective technique to increase their strength [1–3]. Such a refined microstructure can be achieved by processes involving severe plastic deformation (SPD) or compacting ultrafine powders or nanoparticle-sized powders from bulk materials using various powder metallurgy processes Research in this area has been growing rapidly over the last decade, with the main objectives being to increase the productivity of the processes and to understand the deformation mechanisms of these materials better [4–6]
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