Forgings in initial state from AZ31 alloy have homogenous microstructure consisting of equiaxial grains
of mean diameter about 11.2÷15.9 μm, which is characteristic for annealed state (table 1). Changes taking place
in initial material microstructure caused by semi-open die forming process shown on the example of forging
with one rib are presented in Fig. 5. For brackets forgings with two ribs, in the analyzed areas, similar structure
views were obtained. In cross sections of the formed forgings, strong localization of strain was observed in the areas
of material flow in the rib area and in the base under rib (areas 1 and 2 which is shown in macro photos in Fig. 4b).
Material in these areas is upset and squeezed up into the open space limited by side tools surfaces. Microscope
observation showed that in the areas 1and 2 very small recrystallized dynamically grains of mean size about
2.8÷4.7 μm, which is connected with localization of strains large values in these areas (Fig. 5a and 5b). In these
areas, recrystallization process is the most advanced. Moreover, in the rib microstructure in the area 1, additional
primary grains of mean size 11.2÷15.9 μm elongated in the strain direction were localize, which shows that
the recrystallization process in this area is not fully finished (Fig. 5a).
Forgings in initial state from AZ31 alloy have homogenous microstructure consisting of equiaxial grainsof mean diameter about 11.2÷15.9 μm, which is characteristic for annealed state (table 1). Changes taking placein initial material microstructure caused by semi-open die forming process shown on the example of forgingwith one rib are presented in Fig. 5. For brackets forgings with two ribs, in the analyzed areas, similar structureviews were obtained. In cross sections of the formed forgings, strong localization of strain was observed in the areasof material flow in the rib area and in the base under rib (areas 1 and 2 which is shown in macro photos in Fig. 4b).Material in these areas is upset and squeezed up into the open space limited by side tools surfaces. Microscopeobservation showed that in the areas 1and 2 very small recrystallized dynamically grains of mean size about2.8÷4.7 μm, which is connected with localization of strains large values in these areas (Fig. 5a and 5b). In theseareas, recrystallization process is the most advanced. Moreover, in the rib microstructure in the area 1, additionalprimary grains of mean size 11.2÷15.9 μm elongated in the strain direction were localize, which shows thatthe recrystallization process in this area is not fully finished (Fig. 5a).
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