Title: Packed powder diffusion coating of pure aluminium after surface nanocrystallisation

Authors: H-W. Chang, M-X. Zhang

Addresses: Division of Materials, School of Engineering, The University of Queensland, St Lucia, QLD 4072, Australia. ' Division of Materials, School of Engineering, The University of Queensland, St Lucia, QLD 4072, Australia

Abstract: Surface Mechanical Attrition Treatment (SMAT) effectively activates the surface of pure Al and, therefore, lowers the subsequent Packed Powder Diffusion Coating (PPDC) treatment temperature from 600 °C to 560 °C. Although the nanocrystalline grains generated by SMAT in the top surface layer are coarsened during the subsequent heating, the higher volume fraction of grain boundaries associated with the smaller grains formed through recrystallisation within the SMAT affected zone lead to fast atomic diffusion in the PPDC process. Up to 1400 μm thick surface alloyed layer, of which the micro-hardness is 6-10 times higher than the pure Al substrate, can be obtained through PPDC treatment at 560 °C for 24 h after SMAT for 30 min.

Keywords: powder package alloying; surface nanocrystallisation; aluminium alloys; surface mechanical attrition treatment; SMAT; packed powder diffusion coating; PPDC treatment; atomic diffusion; microhardness.

DOI: 10.1504/IJSURFSE.2009.024366

International Journal of Surface Science and Engineering, 2009 Vol.3 No.1/2, pp.125 - 134

Available online: 01 Apr 2009 *

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