امين روزبه

Nowadays, due to the effect of reducing the weight of vehicles in the emission of less carbon dioxide gas, many efforts have been made to use metals with low density. Magnesium and its alloys have advantages such as low density and high specific strength and disadvantages such as low corrosion resistance and low ductility at ambient temperature. In order to develop the applications of magnesium alloys, its joint with aluminum alloys is used. Here, the behavior of the interface created by roll bonding, the determination of the mechanical properties, and the forming limit of Al/Mg two-layer sheet have been investigated experimentally and numerically. In this regard, samples of Al/Mg composite sheet were prepared in two reduction ratios of 40% as the lowest reduction ratio to establish a bonding between aluminum and magnesium and 55% to compare the two reduction ratios. Numerical analysis of the forming limit was done by considering the properties of the diffusion layer at the interface and with the help of the cohesive zone model. The obtained results made it clear that the use of the aforementioned model is able to predict the mechanical characteristics and the forming limit of aluminum/magnesium two-layer composite with a great accuracy; In such a way that the maximum and minimum difference in the comparison between the numerical and experimental results in all limit strains in the Nakazima test is 6.67% and 1.1%, respectively. The results of parametric studies indicate that with the increase of the friction coefficient, the aluminum layer in contact with the punch, and the decrease of the thickness of the layers, the forming limit drops significantly. The eva‎luation of the mechanical properties test shows that with the increase of the reduction ratio (in making the sheet with one pass), the yield strength, ultimate tensile strength, elongation, and FLD0 have decreased by 28%, 23%, 27% and 10%, respectively. In addition, it can be observed that in high reduction ratios, fabricating sheets with two passes and changing the direction of loading in the cross-rolling mode compared compared with the single-pass mode enhances the ultimate tensile strength, composite sheet strain and FLD0 by 15%, 30% and 16% respectively. Therefore, due to the reduction of normal anisotropy, cross rolling has a very good potential for improving the forming limit in the manufacturing of thin sheets.

كامپوزيت آلومينيوم/منيزيوم , پيوند نوردي , فصل مشترك پيوندي , عمليات حرارتي آنيل , دياگرام حد شكل‌دهي , المان محدود

Aluminum/magnesium composite , Roll bonding , Bonded interface , Annealing heat treatment , Forming limit diagram , Finite Element

Amin Roozbeh

Dr. Sedighi