The effect of plating temperatures between 60 and 90 • C on structure and corrosion resistance for electroless NiWP coatings on AZ91D magnesium alloy substrate was investigated. Results show that temperature has a significant influence on the surface morphology and corrosion resistance of the NiWP alloy coating. An increase in temperature will lead to an increase in coating thickness and form a more uniform and dense NiWP coatings. Moreover, cracks were observed by SEM in coating surface and interface at the plating temperature of 90 • C. Coating corrosion resistance is highly dependent on temperature according to polarization curves. The optimum temperature is found to be 80 • C and the possible reasons of corrosion resistance for NiWP coating have been discussed.
The Al9Si0.3Fe0.15Mn alloy was chosen as the base alloy, 0.2Mo and 0.2Zr were added in combination (0.2Mo+0.2Zr) to the base alloy to maintain the ductility and improve the strength in tensile properties. The 0.2Mo+0.2Zr addition alloy showed improvement in both ultimate tensile strength (• UTS ) (160 MPa) and fracture strain (¾ f ) (7.1%) at the as-cast conditions, compared with those (145 MPa, 6.1%) of the base alloy. The increment in the • UTS and ¾ f by 8% and 14%, respectively, was obtained by 0.2Mo+0.2Zr addition. The eutectic ¡-Al with the smallest minimum nanoindentation hardness (H IT, min ), showing high Al or low "Mk e¡ due to heavy micro-segregation existed as a continuous phase in the 0.2Mo+0.2Zr addition alloy led to improvement in ductility. The size of the cell structure caused by the dense tangles of dislocations was about 250 nm, which corresponded to a similar size to the high Al or low "Mk e¡ regions in the 0.2Mo+0.2Zr addition alloy. It was found on the basis of improvement in tensile properties that both usage of the gravity casting method and the addition of Mo and Zr, suggested the possibility for the as-cast application because the eutectic Si particles were refined, and the eutectic ¡-Al phase was characterized by high Al content or low "Mk e¡ region caused by micro-segregation of the Mo and Zr atoms. The inhomogeneity eutectic grains including IMCs acted as the harmonic structure for the improvement in both strength and ductility.
Al1.5 mass%Mn was chosen as the base alloy, and 1.0 and 3.3Si were added to the base alloys, keeping the same values in the "Mk of sorbital energy level as those of Al1.5Mn0.8 and 2.4Mg alloys with superior tensile properties for as-cast applications. The Si addition or increment in the base alloy showed strengthened tensile behavior of the 0.2% proof stress (• 0.2 ) of 67 MPa and ultimate tensile strength (• UTS ) of 160 MPa, although there was reduced in fracture strain (¾ f ) to 9%. The increase and decrease in flow stress and strain, respectively, resulted from the increment in degree of solid solution strengthening by the increase of "Mk of the alloys. There was a good linear relationship between the nanoindentation hardness or rate of elastic deformation work in the ¡-Al phase and • 0.2 of the alloys. The dislocation density of Al1.5MnxSi alloys increased linearly as the "Mk-magnitude increased, compared with that of the base alloy. The behavior in the flow stress variation qualitatively agreed with that of dislocation density. There was a linear relationship between the lattice constant and Mk ¡ in Al1.5MnSi/Mg alloys. As the Mk ¡ changed, the • 0.2 of the alloys also increased and its increment rate was similar in both Si and Mg addition alloys. It may be considered that the trend of change in the lattice constant, • 0.2 , work hardening amount and dislocation density was predominantly consistent with that in the Mk ¡ or "Mk ¡ showing the indication of solid solution hardening level of the ¡-Al phase, and the effect of difference of third elements such as Si and Mg on their mechanical properties could be ignored in tensile examination procedures in this study.
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