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Talita A. Vida,Crystopher Brito,Thiago S. Lima,José E. Spinelli,Noé Cheung,Amauri Garcia 한국물리학회 2019 Current Applied Physics Vol.19 No.4
Zn-Mg alloys are considered to have potential application in bone implants, since both metals are biocompatible and have biodegradable characteristics. Adding Mg to Zn can boost mechanical and corrosion resistances. However, the literature is very limited on quantifying the interrelation of solidification parameters, microstructural features and mechanical/corrosion properties of Zn-Mg alloys. The present study examines the interrelations of alloy Mg content, macrosegregation effects, morphology and scale of the matrix and eutectic phases, nature of intermetallics and tensile and corrosion properties of near-eutectic Zn-Mg alloys. The alloys samples are obtained by unsteady-state directional solidification resulting in a wide range of solidification thermal parameters and microstructures. We examine microstructural features of both dendritic and complex regular eutectic phases. It is shown that the eutectic exhibits a bimodal pattern with neighboring areas of coarse and fine lamellae. Experimental growth laws relating the primary, secondary and eutectic spacings to the solidification cooling rate and growth rate are proposed. Hall-Petch type equations are derived expressing tensile strength and elongation to dendritic and eutectic spacings. Electrochemical parameters determined by polarization curves during corrosion tests and SEM analyses of corroded areas have shown that the alloy having an essentially eutectic microstructure is associated with better corrosion resistance.
Adilson V. Rodrigues,Thiago S. Lima,Talita A. Vida,Crystopher Brito,Amauri Garcia,Noé Cheung 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.5
Al–Cu–Ni alloys are of scientifi c and technological interest due to high strength/high temperature applications, based on thereinforcement originated from the interaction between the Al-rich phase and intermetallic composites. The nature, morphology,size, volume fraction and dispersion of IMCs particles throughout the Al-rich matrix are important factors determiningthe resulting mechanical and chemical properties. The present work aims to evaluate the effect of the addition of 1wt%Ni intoAl–5wt%Cu and Al–15wt%Cu alloys on the solidification rate, macrosegregation, microstructure features and the interrelationsof such characteristics on tensile and corrosion properties. A directional solidification technique is used permitting awide range of microstructural scales to be examined. Experimental growth laws relating the primary and secondary dendriticspacings to growth rate and solidification cooling rate are proposed, and Hall–Petch type equations are derived relating theultimate tensile strength and elongation to the primary dendritic spacing. Considering a compromise between ultimate tensilestrength and corrosion resistance of the examined alloys samples from both alloys castings it is shown that the sampleshaving more refined microstructures are associated with the highest values of such properties.