Sideways extrusion is an advanced technology for one-step production of curved profiles eliminating the need for subsequent bending processes. Its effectiveness in controlling the bending curvature of symmetric products has been well established in prior research. However, there is no report on the effect of asymmetric product shape on bending curvature and still lacking quantitative analysis of welding quality and microstructure of the extrudate for the sideways extrusion, limiting its application scope. In this study, an asymmetric Z-shape aluminium profile was manufactured using sideways extrusion at different speeds and the corresponding numerical simulation was conducted to analyse the extrudate shape, welding quality, microstructural and mechanical properties. The bending mechanism of extrudate, resulting from the non-uniform metal flow during extrusion, was identified. The curvature radius was found to depend on the average exit velocity and the velocity gradient along the transverse direction both of which increase with increasing extrusion speed. Improvements in welding quality and increased recrystallisation fraction during extrusion were quantitatively predicted using developed subroutines and these predications aligned well with the results from post-extrusion examination. In addition, tensile test results differed for profile sections extruded at different speeds, which were attributed to the combined effect of welding quality, work hardening, recovery and continuous dynamic recrystallisation.

Hybrid metal/metal composites are attracting great attention globally for low-carbon manufacturing because they can be ultra-light and have a good combination of mechanical and other desired properties. The application of hybrid metal/metal curved composite profiles to replace traditional curved sections can give full play to the advantages of composite materials. To examine the feasibility of forming such profiles, an aluminium/magnesium metal hybrid curved section was manufactured using a newly developed differential velocity sideways extrusion (DVSE) process. A bimetallic billet comprising a magnesium cylinder enclosed by an aluminium tube was extruded using different speed settings on the two extrusion punches to give precisely controlled radii of curvature in the product. The mechanics of deformation were studied using practical experiments and process modelling, and the microstructural and mechanical properties of the extruded section were determined. It has been demonstrated that the DVSE process with appropriately chosen punch speed settings transforms an initially straight billet with its magnesium core and aluminium cladding into a curved extrudate comprising two discrete magnesium cores surrounded well by aluminium, with a harder surface layer. A monotonic relationship is found between the curvature and the ratio between the speeds of the two punches. The DVSE process induces grain refinement in both the aluminium and magnesium layers with respect to the initial billet. In the aluminium layers, continuous dynamic recrystallisation is the dominant grain refinement mechanism, whereas in the magnesium layers, the fine grains are {1012} tension twins. The present study shows the potential of the novel DVSE process for the production of variable-curvature hybrid metal/metal composites with a good combination of desired properties.

A novel process for fabricating cross-sectional shapes of curved profiles in industrial applications, two-billet differential velocity sideways extrusion (DVSE), is proposed in this study. The feasibility of the process is demonstrated by fabricating solid bars of the aluminium alloy AA1070 through the solid-state welding of two billets at elevated temperature. Microstructural examination has shown that the weld formed between the two billets consists of an unsound area in the dead metal zone within the die and a sound bonding area in the welding zone. Along the welding path, the effective and normal strains gradually increase while the shear strain decreases, leading to the transformation of grains from equiaxed to bamboo-like structures and increases in the hardness, average grain size, and fraction of low angle grain boundaries. The shear strength of the welded extrudate is larger than that of the material without welding. The effective strain in the welding zone is larger than that in other zones. Increasing the temperature or speed of extrusion decreases the unsound bonding area length and the shearing angle, thus improving the uniformity of distribution of the shear strain. The grain diameter is refined from -500 pm in the initial billet to -47 pm in the welding zone of the extrudate formed at 0.05 mm/s and 450 ?. The hardness of the extrudate formed at 400 ?C and 0.1 mm/s is -19 % larger than that of the initial billet, and is decreased by decreasing the extrusion speed or increasing the temperature.

Extruded profiles/sections are increasingly used in the transport industry for lightweight structures. In this paper, a wide thin-ribbed aluminium profile with asymmetric Z-shape, was manufactured by a novel sideways extrusion process proposed by the authors. A comparative study was conducted by utilising the direct/forward extrusion process at the same extrusion temperature and speed, in which the different process mechanics, resulting microstructures and mechanical properties of profiles have been investigated by experiments and finite element modelling. It was revealed that, compared with sideways extrusion, although the design of a die pocket in forward extrusion induces preform and avoids the use of the large-diameter billet and extrusion container/press needed for extruding wide profiles, it requires a greater extrusion force due to work-piece upsetting necessary to fill the die pocket and leads to a lower effective strain in the profile rib. EBSD characterisation of the regions with an equal effective strain indicated that an increased shear strain is more efficient for obtaining fine grains with a higher average misorientation angle. In the same region of the profile rib made from the two different processes, sideways extrusion results in greater grain refinement due to greater effective strains, and a slightly greater texture intensity was found due to the intensive shear deformation. Tensile tests on formed profiles revealed that sideways extrusion leads to a higher yield strength (YS) and ultimate tensile strength (UTS) but a relatively lower elongation to failure, due to the combined effects of grain refinement, GND and texture intensity enhancement. Compared with the billet, the profile formed by forward and sideways extrusion has a YS increased by about 60% and 79% respectively, and an UTS increased by about 74% and 80% respectively in the extrusion direction, demonstrating an advantage of the sideways extrusion process in improving material strength under the same extrusion condition.

Differential velocity sideway extrusion (DVSE) process is a cutting-edge technology to manufacture curved profiles with solid or hollow cross-sections. Extrusion welding is inevitable to form hollow cross-section profiles during DVSE. In the present work, two billets (AA1070) were welded into a bar in the chamber of an extrusion die through DVSE. The material flow behaviour, grain structure and its development in the extruded bar were studied. Based on material flow behaviour, the flow plane of material in the chamber of extrusion die can be divided into metal dead zone (MDZ), shearing intensive zone (SIZ), and metal flow zone (MFZ, including the welding zone). A sound weld without any bonding interface can be obtained by DVSE welding at 500 ℃ and 0.1 mm/s. Before material arrives at the exit of extrusion die, banded structures form along the metal flow direction with the increase of deformation and the mean grain size continually decreases due to dynamic recrystallisation (DRX). Grains significantly grow after exiting from the extrusion die.