Fabrication of High-Strength Lightweight Metals for Armor Applications

Report No. ARL-TR-8800
Authors: Vladimir M Segal, Phillip J Young, Laszlo J Kecskes, Vincent H Hammond
Date/Pages: September 2019; 54 pages
Abstract: This report describes the post-construction modification of the large-scale tooling necessary for the equal channel angular extrusion (ECAE) processing of lightweight structural alloys of AA5083 and AZ31. The "semicontinuous" (sc) ECAE process was successfully demonstrated at a 60- x 60- x 10-cm scale for both alloy systems. However, subsequent conventional rolling operations could not be completed due to failure of the as-rolled billets by "alligatoring". Instead, a roll-forging process was developed to roll the as sc-ECAE processed billets to a 1-inch final thickness. The evolution of the microstructure and properties was also analyzed for the AA5083 and AZ31 alloys, as model materials representing, respectively, the structural refinement under severe plastic deformation by strain-induced formation of sub-grain boundaries and by dynamic recrystallization. For AA5083, the microstructure after sc-ECAE is composed of ultrafine sub-grains that were further transformed into sub-micrometer grains during subsequent rolling. The preliminary solution treatment of AA5083 was found to be an important stabilizing factor in achieving high mechanical properties. For the AZ31 alloy, optimized sc-ECAE resulted in remarkable structural refinement and well-balanced properties with a low number of passes. However, additional rolling in this case led to a degradation of the structure and properties. In the latter part of the project, the key components for transitioning the sc-ECAE process into a semi- to fully automated forging press manufacturing line were identified and their pertinent aspects described.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2019