Numerical and Experimental Investigation on the Surface Defect Generation during the Hot Extrusion of Al6063 Alloy

Abstract

The surface quality control of extruded products is a critical concern in the home appliance manufacturing industry owing to the increasing need for products with a high surface quality, in addition to the essential mechanical properties of the final product. The underlying issue with achieving high-quality extrusion products is that surface defects, especially those resulting in surface gloss differences, called white line defects, are only observed after surface treatment. In this study, we aim to investigate the cause of white line defect generation on the surface of an extruded product. Accordingly, an experimental extrusion program is established using an L-shaped die that has a noticeable change in its bearing length along the inner corner of its cross-sectional profile. Laboratory-scale experiments were performed for the L-shaped extrusion of homogenized Al 6063 alloy at various ram speeds, in order to induce surface defects, considering the production yield rate required for mass production. Subsequently, the microstructural changes near the surface failure region were investigated using an arbitrary Lagrangian–Eulerian (ALE) technique-based thermomechanical finite element (FE) analysis. To scale-up the defect observation method from laboratory-scale to production-scale manufacturing and confirm the reproducibility of the surface defect, scaled-up L-shaped extrusions were performed in an actual industrial production line. Finally, the potential cause of white line defect generation is discussed by comparing the numerical and metallurgical analyses, including the scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) observations.

Highly Efficient Inner Surface Polishing of Fe-Cr-Ni Alloy Cylinder via Isotropically Tuned Electrochemical Etching

“…4 In addition, surface defects generated during the extrusion also worsened the surface roughness. 5 Electric field simulation.-Typically, the as-received surfaces contain protrudes, valleys, and powder particles that affect passivation layer thickness and the local dissolution rate. The as-extruded Fe-Cr-Ni alloy surface exhibits similar features that lead to overall poor morphology, as shown in Figs.…”

“…The inner surface morphologies of the as-extruded cylinders are extremely deteriorated by the surface condition of the die, 3 extrusion parameters such as load, sliding distance, temperature, and pressure, which significantly reinforce plastic deformation 4 and worsen the surface roughness. 5 The high surface roughness of the as-extruded inner surfaces is troublesome for liquid or gas flow and makes them more sensitive to obstruction, corrosion, and mechanical failure. Ramachandran et al 6 discussed that imparting radii with high-quality surfaces improves gas flow and reduces boundary layer turbulence.…”

Influence of Operating Temperature on the Service Life of Aluminum Extrusion Dies

“…A broad discussion of the failure of aluminum extrusion dies has been performed in work by Arif et al [ 12 ]. Research on the impact of speed frames on the surface quality of the extruded aluminum alloy 6063 was carried out in the study by Park et al [ 13 ]. Surface defects occurred only at ram speed of 12 mm∙s −1 .…”