Influence of Chemical Composition of Mg Alloys on Surface Alloying by Diffusion Coating

Nanomechanical properties of Mg–Al intermetallic compounds produced by packed powder diffusion coating (PPDC) on the surface of AZ91E

“…In addition there was Zn in the intermetallic layers, with a somewhat higher concentration towards the surface. This was consistent with that previously reported [19]. intermetallic phases are attributed to their stronger atomic bonds, which are considered to be a mixture of metallic and covalent bonds, because the difference in electronegativity (E) between Mg, Al and Zn is small.…”

“…The container was filled about two thirds with the Mg alloy specimens in the Al and Zn powder mixture, topped up with sand, on which was placed a mixture of sand and charcoal to reduce oxidation of the specimens. The PPDC treatment was carried at 413 °C for 18 hours followed by air cooling to room temperature [5,19]. The temperature of 413 °C was selected because this temperature is typical for solid solution heat treatment for AZ91, and the maximum Al concentration could be obtained in the Mg solid solution without melting due to eutectic formation.…”

“…To overcome hot cracking, Zhang and Kelly [18] developed the packed powder diffusion coating (PPDC) technique, and introduced Zn into the Al powder so that a thick alloy layer was produced on an AZ91D alloy substrate after treatment below 430 °C. Hirmke et al [19] The present research to aims to characterise the mechanical properties of these intermetallic phases in-situ in such coatings using nanoindentation.…”

A study of the deformation and failure mechanisms of protective intermetallic coatings on AZ91 Mg alloys using microcantilever bending

“…The density of the precipitates declines within 1 μm of the interface, which is likely attributed to the depletion of Al. The Al depletion is the result of Al diffusion toward the boundary to feed the growth of β-Mg 17 Al 12 layer into the AZ91 substrate [6,13]. Fig.…”

“…A packed powder diffusion coating (PPDC) technique using Al and Zn mixed powders as the diffusion source was successfully applied to obtain thick polycrystalline β-Mg 17 Al 12 and τ-Mg 32 (Al, Zn) 49 intermetallic layers on Mg alloys. This process has proven to be effective at providing protection from both wear and corrosion for Mg alloys [6,13]. The intermetallic layers exhibited high hardness (approximately a fourfold increase over bulk Mg [14]) and the corrosion resistance of both β-Mg 17 Al 12 and τ-Mg 32 (Al, Zn) 49 phases in NaCl solution was found to be one to two orders of magnitude higher than that of AZ91 Mg alloys [6,9,15].…”