It is known in cold rolled 3104 aluminum alloy sheets that ears on a cup are formed by deep drawing in 0° and 180° against the rolling direction. Previous reports discussed the relationship between crystallographic texture on original sheet and the ears, however, significant correlation wasn’t necessarily observed between anisotropy of the mechanical property and the ears. In order to know the mechanism of ear forming by deep drawing, texture development by deep drawing should be considered. In the present work, development of deformation texture in cold rolled 3104 aluminum alloy sheets by deep drawing was measured by X-ray diffraction method and then analyzed. Major orientations found in the deformation texture by deep drawing were similar to rolling texture, however, intensities of the Goss and Cu components were especially increased. Lattice rotation by deep drawing was estimated by analyzing orientation distribution function (ODF) and the crystallographic mechanism of the texture development was discussed.
An Al–7.3 mass%Mg-based alloy with high strength and good hot rollability was developed by addition of grain boundary strengthening element. We predicted that Fe is the most effective element for grain boundary strengthening at 773 K from first-principles calculations. Then, an Al–7.3%Mg–62 ppmFe alloy and Al–7.3%Mg–124 ppmFe alloy were developed. Grain boundary analysis by HAADF-STEM revealed that added Fe segregated at grain boundaries in the Al–111 ppmFe alloy. The Al–7.3%Mg–62 ppmFe alloy and Al–7.3%Mg–124 ppmFe alloy exhibited good workability without crack by intergranular fracture, whereas an Al–7.3%Mg alloy exhibited poor workability with crack by intergranular fracture at 298–623 K. Also, the Al–7.3%Mg–124 ppmFe alloy showed the best workability, and when the Fe concentration was below the solid solubility limit, the workability improved as the amount of Fe added increased. We succeeded in developing a high strength Al–7.3%Mg–124 ppmFe alloy with good workability.
Deformation behavior of a 5000-series aluminum alloy sheet under biaxial stress is precisely measured for linear stress paths, using servo-controlled biaxial tensile tests with cruciform specimens. Successive contours of plastic work in stress space and the directions of the plastic strain rates are precisely measured and compared with those calculated using the Yld2000-2d (Barlat et al., 2003) and Yld2004-18p (Barlat et al., 2005) yield functions. Both yield functions successfully reproduce the successive work contours and the directions of the plastic strain rates of the test material. In order to check the effect of the yield functions on the enhancement of the predictive accuracy of forming simulations a finite element analysis of hole expansion forming is performed using the yield functions. The calculated thickness strain distributions are compared with experimental ones. The prediction by the Yld2004-18pyield function using solid elements had the closest agreement with the experimental data by considering the drawbead forming process and the material deformation behavior passing over the draw-bead during the hole expansion forming process.
Magnesium has the lowest density among the engineering metallic materials and significant weight reduction can be achieved if magnesium alloys are used in automobiles, trains, airplanes, etc. However, they have some practical limitations in mechanical properties and corrosion resistance compared with other metallic materials. Generally, grain refinement is an effective way for enhancing the strength of metallic materials, and it has been reported that the grain refinement is very effective to strengthen the magnesium alloys. In this study, the influence of grain size on the tensile properties of three magnesium alloys has been investigated using specimens having grain sizes ranging from 100 nm to 100 µm. The grain size was changed by heat treatment after HPT processing, and the tensile tests have been made at an initial strain rate of 1.0×10−4 s−1. The grain refinement is effective for strengthening in the coarse-grained samples in which grain size is larger than 3 µm, but its effect decreases significantly in the fine-grained samples in which grain size is below 3 µm. This difference in effect of grain refinement has been discussed in relation to deformation mechanism.