Publikacje

Abstract:

Surface layers enriched with zinc were formed on pure magnesium and AZ91 alloy
by heating the specimens in contact with paste containing zinc chloride and potassium
chloride at 440 8C for 2 h, using no protective atmosphere. The study involved
determining the microstructure, phase composition and microhardness of the resulting
layers. During the layer formation process, a transient liquid phase occurred
at the substrate/paste interface. The layers fabricated on both substrates were
about 200 mm in thickness and they were metallurgically bonded to the substrate
material. The same process conditions were used for both types of substrates.
From the experimental data it is clear that the layer fabricated on magnesium differed
in microstructure from that formed on AZ91. The alloyed layer on magnesium
was characterised by dendrites of a solid solution of zinc in magnesium surrounded
by a lamellar eutectoid structure composed of an MgZn intermetallic phase and a
solid solution of zinc in magnesium. In the layer formed on AZ91, aluminium was
detected in all the structural constituents. The layer was composed of a solid solution
of zinc and aluminium in magnesium and Mg17(Al, Zn)12 and Mg5Al2Zn2 intermetallic
phases. The alloyed layers had much higher hardness than the substrate
materials.

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Surface alloying of magnesium and AZ91 by thermochemical treatment in a medium containing zinc chloride and potassium chloride