Yield surfaces of A5052 aluminum alloy sheets with different tempers are modeled by the simplified identification method using the circumscribing polygon. In this method, a polygon circumscribing the equal plastic work contour is determined by uniaxial tensile, equal biaxial tensile and plane strain tensile tests. Anisotropic yield surfaces of A5052 aluminum alloy sheet are modeled by Yld2000-2d (Barlat et al., 2003) and Yld2004-18p (Barlat et al., 2005) yield functions. Both yield functions can express the inscribed curves of the polygons. The modeled yield surfaces of A5052-O agree with the stress points of the equal plastic work contours measured by the reliable bi-axial tensile tests. The proposed method to identify the yield function is effective for aluminum sheet metal. On the other hand, the two identified yield functions show different in-plane plastic anisotropy in the tension-compression combined stress state. To examine the suitability of identified models, the experiments and numerical analyses of the deep drawing tests are carried out. Comparing the experimental and analyzed results, the predicted ear height of drawn cup using the Yld2004-18p yield function agree with experimental results qualitatively. But the prediction of the ear using the Yld2000-2d cannot express the tendency of the experimental one.
In recent years, it has been reported that intermetallic compound particles can suppress hydrogen embrittlement by hydrogen trapping into them. Some intermetallic particles in aluminum alloys, such as Al7Cu2Fe, have internal hydrogen trap sites and it is proposed that hydrogen embrittlement can be suppressed by preferential hydrogen partitioning to these sites. However, intermetallic compound particles act as fracture origin, and excessive addition degrades the mechanical properties. In this study, we quantitatively evaluated the damage and decohesion behavior of intermetallic compound particles in high-hydrogen 7XXX aluminum alloys by using in-situ synchrotron radiation X-ray tomography. As the results, it has been revealed that hydrogen induced early high-strain localization, and the Al7Cu2Fe particles were damaged in that region due to own brittleness, resulting in early fracture. Hydrogen had no effect on the fracture and debonding behavior of intermetallic compound particles, suggesting that observed brittle fracture of particles is dependent on the mechanical properties of the particles.
The effect of multi-directional forging on the development of texture and increase of hardness was investigated for a commercial A5052 aluminum alloy, which had an initial texture with a major orientation of ｛001｝<100>. Two specimens were prepared: one was obtained via multi-directional forging (MDF) performed four times at a true strain of 0.18 for each forging, while the other was prepared via unidirectional forging (UDF) performed one time at a true strain of 0.72. The specimens obtained via MDF and UDF at the same true strain of 0.72 exhibited the same tendencies in terms of hardness, grain diameter, and Kernel average misorientation (KAM) value. The specimen after undergoing MDF four times had a deformation texture with major and minor orientations of ｛011｝<100> and ｛011｝<110>, respectively. The formation of ｛011｝<100> can be explained using the Sachs model, in which slip systems undergoing maximum resolved shear stress are activated during MDF. Furthermore, it was concluded that the formation of ｛011｝<110> after the specimen underwent MDF four times was caused by the appearance of ｛001｝<110> after performing the MDF of the specimen for three times.
Al-Mg-Ge alloys are considered to exhibit similar aging behavior as Al-Mg-Si alloys, therefore, they have been alternatively used to analyze precipitates in Al-Mg-Si alloys. However, the interactions between solute atoms and vacancies in Al-Mg-Ge alloys are not clear. In this study, the binding energies between solute atoms and between solute atoms and vacancies in Al-Mg-Si and Al-Mg-Ge alloys were investigated using first-principles calculations, and the similarities and differences of biding energy in each alloy were analyzed. Comparing the three-body binding energy, the Mg-Ge-vacancy interaction in the Al matrix was stronger than the Mg-Si-vacancy interaction. The difference in the bond strength could be explained by the difference in the atomic radii against the Al atom. However, the binding energy change with different bond angles was consistent for the Si and Ge cases. These results indicate that similar interactions between solute atoms and vacancies are one of the reasons for the formation of similar precipitates in Al-Mg-Si and Al-Mg-Ge alloys. In addition, the strong interactions between solute atoms and vacancies in Al-Mg-Ge alloys suggest that the clustering occurs more rapidly than in Al-Mg-Si alloys, resulting in a rapid increase of hardness at the early stage of precipitation.