The flaky structure in fractures of extruded articles of the D16 aluminum alloy
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We have found that flakiness in fractures of the D16 alloy has the following effects.
The depressions in the fracture coincide with the boundaries of elongated uncrystallized grains.
The flaky structure is particularly manifest when the concentration of ion and silicon in the alloy is low.
The degree of flakiness depends on the diameter of the ingot and on the casting rate.
Heating (homogenization) of ingots and rods decreases the degree of flakiness.
The flaky structure in the fractures of extruded rods of the D16 alloy results from the irregular flow of separate fibers during breaking of the samples, when the ductility of the grain boundaries is low. The irregular flow is due to the heterogeneity of the composition of the alloy in microvolumes (intercrystalline liquation) and is not related to the concentration or distribution of secondary phases.
The presence of rough flakiness in fractures of the D16 alloy does not affect its strength in the transverse or longitudinal directions, but decreases the elongation and the impact strength in the transverse direction.
The flaky structure in fractures of D16 rods can be eliminated or decreased by high-temperature (515°C) homogenization of the ingots or high-temperature treatment of the rods, and also by regulating the concentration of iron and silicon in the alloy.
KeywordsIron Aluminum Silicon Depression Ductility
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