Abstract:Severe surface roughening during plastic deforming of aluminum alloy parts can produce “orange peel” defects. To analyze “orange peel” of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoidal specimens were carried out. The tubes with different grain sizes were obtained by spinning and subsequent annealing heat treatment. The macroscopical behavior of surface roughening was characterized by surface roughness Ra using a laser scanning confocal microscope. The corresponding microscopic behavior was reflected by microstructures of specimens and in-situ observation using electron back-scattered diffraction (EBSD). The obtained results show that the surface roughness increased firstly with increasing strain and then decreased slightly. There was a critical strain for aluminum alloy tube, below which “orange peel” defect would not occur. For the tube with a mean grain size of 80, 105, 130 and 175 μm, the critical strains were 10.17%, 5.74%, 3.15% and 1.62%, respectively. Meanwhile, the surface roughening behavior was produced by serious inhomogeneous deformation between grains as strain increased, and was aggravated as the grain size increased due to the larger local deformation in larger grains.

Key words: 6063 aluminum alloy; surface roughening; tensile deformation; spinning; orange peel