Improvement in corrosion resistance of Mg_(97)Zn_(1)Y_(2)alloy by Zr addition

Magnesium alloys,known for their exceptional lightweight properties,have presented challenges in various applications due to their limited corrosion resistance.In this study,the corrosion resistance of Mg_(97)Zn_(1)Y_(2)magnesium alloys was enhanced by incorporating Zr elements into the Mg_(97)Zn_(1)Y_(2)matrix,which is distinguished by long periodic stacking ordered(LPSO)phases.Results show that Mg_(97)Zn_(1)Y_(2)-xwt.%Zr(x=0,0.1,0.3,0.6)alloys containing Zr exhibit reduced hydrogen evolution rates and decreased corrosion levels compared with that without Zr,when immersed in a 3.5wt.%NaCl solution.Addition of 0.3wt.%Zr results in the most significant improvement,with a corrosion rate as low as 2.261 mL·cm^(-2),representing an 86%reduction from 16.438 mL·cm^(-2)of the base alloy.Furthermore,alloys with Zr additions demonstrate a more positive corrosion potential and lower corrosion current density than does the matrix alloy(64.92μA·cm^(-2)).The lowest corrosion current density,21.61μA·cm^(-2),occurs with the addition of 0.3wt.%Zr.The introduction of Zr induces a change in the microstructure of the LPSO phases,increasing the charge transfer resistance within the alloy and thus effectively improving its corrosion resistance.

Aging kinetics of 14H-LPSO precipitates in Mg-Zn-Y alloy

Alloys with long-period stacking ordered structures(LPSO)have good properties and are highly regarded.Mg-Zn-Y alloy containing LPSO phase was prepared by the traditional casting method,and the aging heat treatment was performed at different temperatures and times.The microstructure and phase constitutions of the alloy were observed by means of optical microscopy and scanning electron microscopy methods.Results show the microstructure of as-cast Mg95.5Zn1.5Y3 mainly consists ofα-Mg,W phases and LPSO phases.During the aging treatment,fine lamellar-shaped 14H-LPSO phase is formed at the grain boundaries and precipitates from the supersaturated magnesium matrix,and the volume fraction increases as the aging time increases.By controlling the aging time,Mg-Zn-Y alloys with different volume fractions of 14H-LPSO phase were prepared.The aging kinetics equation of the 14H-LPSO phase is summarized,that is f=1-exp(-0.2705 t 0.6368).The phase transformation mechanism of 14H-LPSO in Mg95.5Zn1.5Y3 alloy can be described as the change of dislocation energy.

Corrosion and chemical behavior of Mg_(97)Zn_(1)Y_(2)-1wt.%SiC under different corrosion solutions

To explore the corrosion properties of magnesium alloys, the chemical behavior of a high strength Mg_(97)Zn_(1)Y_(2)-1 wt.%Si C alloy in different corrosion environments was studied. Three solutions of 0.2 mol·L^(-1) NaCl, Na_(2)SO_(4) and NaNO_(3) were selected as corrosion solutions. The microstructures, corrosion rate, corrosion potential, and mechanism were investigated qualitatively and quantitatively by optical microscopy(OM), scanning electron microscopy(SEM), immersion testing experiment, and electrochemical test. Microstructure observation shows that the Mg_(97) Zn_(1)Y_(2)-1 wt.%Si C alloy is composed of α-Mg matrix, LPSO(Mg_(12) ZnY) phase and Si C phase. The hydrogen evolution and electrochemical test results reflect that the Mg_(97)Zn_(1)Y_(2)-1 wt.%SiC in 0.2 mol·L^(-1) Na Cl solution has the fastest corrosion rate, followed by Na_(2)SO_(4) and NaNO_(3) solutions, and that the charge-transfer resistance presents the contrary trend and decreases in turn.