Al–Mg–Si alloys are suitable materials for automotive body application because of a good formability, a good corrosion resistance and a satisfactory strengthening. However, it is well known that when some kinds of Al–Mg–Si alloy sheets are stretched along the transverse direction, rope-like profiles (ridging/roping) parallel to the rolling direction develop on the surface. The purpose of this study is to clarify the ridging development in Al–Mg–Si alloy (6111 aluminum alloy). The effect of thermo-mechanical treatment on ridging development was investigated by 3D profile microscope and SEM/EBSD method. Rope-like profiles tended to develop remarkably in the hot-rolled and intermediate-annealed sheets. In highly ridging developed sample, there were many bands of cube-oriented grains (cube bands). Therefore, in this study, the cube-oriented grain formation process was also investigated by SEM/EBSD and TEM observation. Microstructure observations revealed that cube-oriented grains formed during the hot rolling process could remain due to rod-like precipitates in grain. And then, these cube-oriented grains were grown along the rolling direction during the intermediate annealing. Crystal orientation analysis shows the stored energy of the cube-oriented grains in the cold rolled sheet was lower than that of other-oriented grains. Therefore, we concluded that cube bands are preferentially formed during solutionized treatment.
In the production of cups or containers by conventional deep drawing, the limiting drawing ratio obtained during the first drawing is very minimal. Therefore, to make deep cups, redrawing or ironing in one or more subsequent stages is necessary. An innovative method of producing very deep cups by employing a developed blank was previously proposed. In this method, the drawing resistance of the blank is reduced drastically, and so deep cups can be obtained at the first drawing. However, the drawn cup has seams in the side wall. To make an airtight cup, the seams must be joined. In this study, a new method of forming deep cups by using the developed blank was investigated. The developed blank is drawn with a punch, and friction stir welding (FSW) is conducted simultaneously to join the seams formed in the side wall. A rotation probe is put on the flange contact point and friction heat is generated, thus joining the seam parts. The experimental results show that the production of a very deep and airtight cup in a single process can be successfully accomplished with this proposed method.
In this paper, the phenomenon of intergranular fracture in a peak-aged Al–6.7%Zn–2.8%Mg–0.4%Cu alloy has been investigated by an electron backscattered diffraction (EBSD) technique and the effect of crystallographic orientation on the crack propagation was clarified. Individual grain boundaries were divided into four groups based on their difference in Schmidt factor (S.F.) and stress transfer factor (Nij). The difference in S.F. higher than 0.05 corresponds with the groups A and B and lower that 0.05 is characteristic for the groups C and D. Nij factor higher than 0.5 is specific for the groups A and C and the groups B and D having this factor lower than 0.5. It has been found that grainboundary fracture occurs at the boundaries belonging to the group D in 46% of all cases, in 24% corresponding with the group B and in 23% with the group C. Preferential deformation in the vicinity of grainboundaries belonging to the group B has been also verified by an atomic force microscopy (AFM) technique as the same as a case in the peak-aged Al–Mg–Si alloy.