English abstract
The aim of this study is to recycle AZ31 (UNS M11311) magnesium alloy chips by solidstate recycling (SSR) approach utilizing a severe plastic deformation technique. The equal
channel angular pressing (ECAP) as a severe plastic deformation technique is used to
consolidate the AZ31 chips into bulk material. ECAP was originally used to process bulk
materials to enhance their mechanical properties due to its large imposed strain. Hence,
it is recently used to successfully consolidate metallic powder and chips. In addition to the
successful overcoming of the environmental, economical, and technical issues of
recycling Mg alloy using conventional remelting process, starting with chips with
different orientation during SSR process might result in material with weaker
crystallographic texture and hence lower anisotropy. In the current study the quality of
consolidation is investigated as a function of ECAP passes. Detailed metallographical,
chemical and mechanical characterization as well as texture simulation were carried out
on the recycled AZ31 samples.
The AZ31 Mg alloy chips have been successfully recycled using one and two ECAP
passes following route A in which the billet is continuously processed without rotation
between successive passes. The degree of consolidation quality was found to be highly
dependent on the number of ECAP passes. The density of recycled material was
significantly improved by increasing the number of passes. Furthermore, the hardness of
solid state recycled AZ31 materials was found to be higher than those of the starting cast
AZ31 and it increases with increasing number of passes. The breakage of oxide layers
around the chips boundaries and the distribution of the oxide particles within the matrix
have caused particles dispersion strengthening and hence increased in hardness. The
texture evolution of solid state recycled AZ31 after one pass and two passes was
successfully predicted using a visco-plastic self-consistent (VPSC) crystal plasticity
model. It was found that the recycled AZ31 samples using ECAP developed strong texture
despite the starting random texture. The recycled AZ31 exhibited a strong basal texture
that was further strengthened after the second ECAP pass following route A.
