After the simulations, it was clear that better forging occurred, unlike the previously-analyzed case, in the front and back zones of the forging. This extensive and uniform forging is possible only in flat anvil forging, where the metal can flow freely in both directions along the z-axis. In the studied cases, such flow feature was absent; thus, the number of forging passes needed to obtain a uniform area of the forging with a higher effective strain value was greater than in the previous tests. It was also observed that some effective strain values were significantly higher than during the previous test. This difference can be explained by the fact that the deeper areas of the forging were not forged well due to the formed cracks in the surface of the material. Casting defects, such as cooling channels, are also related to the deteriorated mechanical properties of forged magnesium alloys. However, in the forged AZ91 BSP samples, only a small number of cooling channels was observed; therefore, such defects do not seem to have generated a significant number of hot spots in the material, since an adequate annealing time was also observed. Therefore, a high-quality and homogeneous microstructure was obtained, which led to good mechanical properties of the samples.
Based on the data in Figure 18c, it can be observed that the overall forging was homogeneous. The analysis of the effective strain distribution in the areas of the forged material shows that the front and back areas of the forged material were of lower effective strain values than the central area of the forging. In addition, the areas along the z-axis of the forging were of higher effective strain values. These areas correspond to the central zone with the maximum effective strain values obtained in the previous test (See Figure 17). The distribution of the calculated effective strain values in the material of the analysed sample of components was homogeneous, which corresponded to the large-scale forging performed in the analysis. In the forged magnesium alloy AZ91 BSP samples, there was an influence of the initial microstructure of the billet samples and the direction of the stresses in different sections of the material during forging on the fracture crack formation. As it can be observed in Figure 18d, the crack occurred in the forge/heat affected zone. d2c66b5586