Shangming He

Microstructure, Mechanical Properties, Creep and Corrosion Resistance of Mg-Gd-Y-Zr(-Ca) Alloys

The microstructure, mechanical properties, creep and corrosion resistance of Mg-Gd-Y-Zr(-Ca) alloys were studied. Small additions of 0.4-0.6 wt% Ca to Mg-(9-10)Gd-3Y-0.4Zr(wt.%) alloys led to a slight improvement in creep resistance and a remarkable increase in corrosion resistance, but an obvious decrease in elongation to fracture. UTS and TYS of the Mg-Gd-Y-Zr(-Ca) alloys are obviously higher than those of WE54, especially in the temperature range from room temperature to 200 oC. TEM images and corresponding energy dispersive x-ray spectra showed that the Ca element primarily segregated to the grain boundaries and existed in the cuboid-shaped particles with a trace concentration, and the small addition of Ca had no obvious effect on the orientation, morphology, and distribution of β′ phase, which is responsible for the peak hardness in Mg-Gd-Y-Zr alloys.

Effects of Variable La/Ce Ratio on Microstructure and Mechanical Properties of Mg-5Al-0.3Mn-1RE Alloys

Effects of variable La/Ce ratio on microstructure and mechanical properties of Mg-5Al-0.3Mn-1RE alloys were investigated. The results indicated that pure La or pure Ce can improve ultimate strength and yield strength of AM50 effectively without obvious decrease of elongation, and the effect of La is better than that of Ce. However, addition of La and Ce together deteriorates the mechanical properties of AM50, and the valley of mechanical properties mostly appears on La:Ce= 1:1. The existence of coarse skeleton-like phase and less amount of Mg17Al12 phase is responsible for this.

Application of Electrochemical Techniques to Characterization of the Corrosion Behaviors of GW63 Alloys

The corrosion behavior of GW63 (Mg-6wt.%Gd-3wt.%Y-0.4wt.%Zr) alloys in 5% NaCl aqueous solution has been investigated by PARSTAT 2273 instrument. The Open Circuit Potential (ECORR) vs. time curve, cyclic polarization (Pitting Scans) curve and Electrochemical Impedance Spectroscopy (EIS) was measured for the GW63 alloys in as-cast and T6 heat treatment conditions. The EIS results indicated that the tendency of impedance variation for as-cast condition was monotonic decreasing, however, the tendency of variation for T6 condition was not completely monotonic but the total tendency was decreasing. The values of impedance of GW63 alloy at 0.1 Hz are about 103 ohm-cm2 for as-cast and T6 condition.