OBRABOTKAMETALLOV technology Vol. 25 No. 3 2023 performed in two passes, where the first pass was equal to 45 %, and the second one corresponded to the target final reduction (from 55 to 75 %). The authors experimentally determined that bonding between aluminum alloys occurs when the thickness reduction ε is not less than 45 %. This observation is consistent with the literature. For example, in [6], it was established that a thickness reduction of at least 40 % is required for joining sheets from commercially pure aluminum. Results and discussion Fig. 2a, b shows the shape change of the coordinate grid, which characterizes the flow of the middle layer during rolling with a reduction of 45 and 75 %, respectively. The coordinate grid was built in the central longitudinal section with a cell size of 0.5 × 0.5 mm. From the shape change of the grid, one can note that the near-surface layers of the D16 alloy flow in the longitudinal direction more intensively than the central layers of the alloy during rolling. At higher reduction ratio, as shown in fig. 2b, there is a more intensive elongation of the near-surface layers of the D16 alloy compared to the central ones. а b Fig. 2. Shape change of the central layer grid under rolling with thickness reduction ratio of 45 % (a) and 75 % (b) Fig. 3 shows the flow of metal to the exit from the deformation zone. One can note that there is a curvature of the flow velocity vectors surface of the metal layers with a lag in the flow of the central layer of D16 alloy compared to the outer layers from AMg3 alloy. In other words, the metal of the central layer is displaced toward the entrance to the deformation zone due to its lower deformation resistance. Based on this, it is obvious that the law of constancy of second volumes is not fulfilled with the corresponding distortion of the coordinate grid. To evaluate the strain inhomogeneity in the cross section of the rolled composites, the effective strain ei was measured along the line shown schematically in fig. 2. The effective strain ei was calculated as per the equation ( ) ( ) ( ) 2 2 2 1 2 2 3 3 1 2 3 i e e e e e e e = − + − + − , where e1–e3 are the principal strains. The measurement results are presented as a graph in fig. 4, where the relative thickness of the laminated
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