Specific Features of Microstructural Evolution During Hot Rolling of the As-Cast Magnesium-Rich Aluminum Alloys with Add
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e used in almost in all present-day products,[1–4] while flat-rolled aluminum products are the most frequently produced industrial semifinished products.[5] The major goal in producing flat-rolled aluminum is to obtain flat-rolled products with preset mechanical properties, as required by the specific end use. The specified set of mechanical properties can be achieved by managing the microstructure and substructure sizes and controlling the aluminum sheet and coil texture.[6] This task can be achieved by E.V. ARYSHENSKII is with the Samara State Aerospace University, Samara National Research University, Moskovskoye Shosse 34, Samara, Russia, 443086 and also with TU Bergakademie Freiberg, Institut fu¨r Metallformung, Bernhard-von-Cotta-Str. 4, 09599 Freiberg, Germany. Contact e-mail: [email protected] J. HIRSCH is with the Samara State Aerospace University, Samara National Research University and with the Hydro Aluminium Rolled Products GmbH, Research and Development, 53117 Bonn, Germany and also with Aluminium Consulting, 53639 Ko¨nigswinter, Germany. S.V. KONOVALOV is with the Samara State Aerospace University, Samara National Research University. U. PRAHL is with the TU Bergakademie Freiberg, Institut fu¨r Metallformung. Manuscript submitted January 9, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
employing the correct thermomechanical practices during the flat-rolled plate and sheet fabrication,[7–14] where the microstructural evolution is controlled during each stage of the sheet processing. The microstructural evolution resulting from a previous stage (e.g., the evolution of grain sizes, main texture orientations, second-phase particle volume fractions) will always have an immediate effect on the next stage results. Therefore, the microstructural evolution should be managed during early processing, such as during the as-cast structure deformation. The as-cast ingot microstructure differs from the microstructure observed in the subsequent stages of the plate and sheet rolling, in which coarser initial grain sizes are typical, compared to those observed in the finishing stages of sheet and strip production. The fine grain structure observed in subsequent stages is associated with longer intergrain boundaries and, hence, a higher stored nonequilibrium grain boundary energy.[15] In addition, a long intergrain boundary leads to a larger number of new structure nuclei and, hence, a more intensive recrystallization process. On the other hand, research shows that intermetallic ‘‘constituent’’ particles gradually decrease in size (due to crushing) during hot rolling.[16] Thus,
these particles initially have larger sizes, which allows more for the PSN (particle stimulated nucleation) mechanism to be triggered more efficiently.[6,7,15] Therefore, the microstructure that forms during the early stages of the thermomechanical treatment differs from that observed during the subsequent stages. Multiple studies have addressed the texture, structure, and substructure evolution issues as a function of the thermomechanical treatments.[
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