TABLE OF CONTENTS By the term substructure we will understand, as it was pointed out in Section 2.1, the internal structure of dendritic cells of (Al) solid solution. For casting aluminum alloys it is studied insufficiently. A significant part of the experimental studies in this field is related to single crystals, most often of pure metals with small amounts of admixtures and/or alloying elements (see, e.g., [148 155]). At the same time, conditions of solidification of polycrystalline industrial alloys differ significantly from those in which single crystals are grown. Correspondingly, the substructure of such alloys also must be different.
Fine structure of metals and alloys exerts a very strong influence upon their properties. By the same token it may be stated that the properties of casting aluminum alloys also should depend, to a certain degree, upon their substructure.
In 1940s Bochvar formulated an important hypothesis, according to which even crystals of Al-based solid solution that look completely homogeneous under a microscope, in reality possess a certain substructure forming due to the dendritic nature of their growth [156]. At the same time Bochvar clearly identified the need for direct studies of dendrite microstructure using electron microscopes [156, 157]. In this section we describe the results of systematic XRD and electron microscopy studies of the role and influence of alloying and solidification conditions upon the dislocation structure inside dendritic cells of aluminum solid solution and also its decomposition after cooling and solidification (see mostly [122, 158 161]).
