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By using CeO2particles instead of part of Al2O3particles as filler, the CeO2was successfully entrapped into the outer layer of the chromizing coatings on the as-deposited nanocrystalline (NC) and microcrystalline (MC) Ni films using a conventional pack-cementation method at 800 °C. For comparison, chromizing was also performed under the same condition on MC Ni film using Al2O3as filler without CeO2particles. SEM/EDX and TEM results indicate that the refinement of Ni grain and CeO2entrapped into the chromizing coatings refine the grain of the chromizing coating. Oxidation at 900 °C indicates that compared with the CeO2-free chromizing coating, the CeO2-dispersed chromizing coating exhibits an increased oxidation resistance. For the CeO2-dispersed chromizing coating, the refinement of Ni grain size significantly decreases the transient-oxidation scaling rate of the chromizing coatings. Together with this, the CeO2-dispersed chromizing coating formed on NC Ni exhibits a better oxidation resistance.

Reactive reactive element oxide RexOy (Re=Ce, Y)-modified aluminide coatings were developed by aluminizing the as-codeposited Ni-RexOy composite film using pack cementation method at 1100℃ for 4 h. By comparison, aluminizing was also performed with the same condition on an as-deposited Ni film without RexOy particles. SEM/EDAX and TEM results indicated that the co-deposited CeO2 or Y2O3 particls were homogeneously dispersed in the finer-grain nanocrystalline Ni grains. The cyclic oxidation in air at 900℃ indicated that the RexOy -modified aluminide coatings were profoundly spallation resistance as compared to the RexOy -free coatings due to the formation of a continuous adherent α-Al2O3 scale.

The solidification microstructure and the microhardness of Al-11Mg-4.5Zn alloy under high pressure were researched by optical microscope, scanning electron microscope (SEM), X-ray diffraction(XRD) and microhardness tester. The results revealed that high pressure solidification refined the dendrite structure, and made the primary dendrite arms grow long. The alloy all consisted of α-Al phase and Mg32(Al, Zn)49 phase whether under normal pressure or high pressure solidification conditions. However, the morphology of the Mg32(Al, Zn)49 phases changed from fork-like of normal pressure to the graininess of high pressure, the size of them reduced, and that of the amount decreased. Furthermore, the solid solubility of Mg and Zn in α-Al phase increased comparing with those of normal pressure, and they were the largest at 4GPa high pressure, reaching 11.37% and 4.15%, respectively. The microhardness of Al-Mg-Zn alloy had an increment with the pressure increasing.

Reactive reactive element oxide RexOy (Re=Ce, Y)-modified aluminide coatings have been developed by the first step of co-electrodeposition of Ni with CeO2 or Y2O3 particls on pure Ni and the subsequent step of diffusional aluminizing on electrodeposited Ni-CeO2/or Y2O3 composite films using pack cementation method at 1100OC for 4 hr. By comparison, aluminizing was also performed with the same condition on an as-deposited Ni film without RexOy particles. The oxidation in air at 900OC indicated that the RexOy (Re=Ce, Y)-modified aluminide coatings were profoundly oxidation resistance as compared to the RexOy (Re=Ce, Y)-free coatings. The effect of CeO2 or Y2O3 on the oxidation behavior is discussed in detail.