In order to improve the corrosion and mechanical properties of AM50 magnesium alloy, 1 wt.% Gd was used to modify the AM50 magnesium alloy. The microstructure, corrosion and mechanical properties were evaluated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, electrochemical and mechanical stretch methods. The results indicated that β-Mg17Al12 phase decreased and Al2Gd3 and Al0.4GdMn1.6 phase existed after Gd addition. Because of the Gd addition, the grain of AM50 magnesium alloy was refined significantly, which improved the tensile strength of AM50 magnesium al-loy. The decreasing ofβ phase improved the corrosion resistance of the magnesium alloy. The fracture mechanism of the Gd modified AM50 magnesium alloy was quasi-cleavage fracture. The corrosion residual strength （CRS） of AM50 magnesium alloy was im-proved after 1 wt.% Gd addition.
Microstructures and mechanical properties of extruded Mg-2Sn-xYb(x=0,0.1,0.5 at.%)sheets were investigated.The grain size of as-cast Mg-2Sn alloy is significantly reduced with increasing Yb concentration.In addition toα-Mg and Mg_(2)Sn phase,some fine Mg_(2)(Sn,Yb)particles are observed in as-cast Mg-2Sn-0.5Yb alloy,but these fine particles are not observed in as-cast Mg-2Sn-0.1Yb alloy due to a high solubility of Yb in Mg matrix.Tensile tests demonstrated that extruded Mg-2Sn-0.5Yb sheet exhibited the highest tensile strength and available elongation to failure at room temperature,while extruded Mg-2Sn-0.1Yb alloy exhibited the highest tensile properties at 100°C and 200°C.The difference in the tensile properties of extruded sheets mainly arises from the different strengthening roles of grain refinement,solid solution strengthening and precipitation strengthening of particles.
Effects of cold rolling deformation on the microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel （HNASS） are investigated. Microstructure characterization shows that 70% cold rolling deformation results in significant refinement of the microstructure of this steel, with its average twin thickness reducing from 6.4 μm to 14 nm. Nanoindentation tests at different strain rates demonstrate that the hardness of the steel with nano-scale twins （nt-HNASS） is about 2 times as high as that of steel with micro-scale twins （mt-HNASS）. The hardness of nt-HNASS exhibits a pronounced strain rate dependence with a strain rate sensitivity （m value） of 0.0319, which is far higher than that of mt-HNASS （m = 0.0029）. nt-HNASS shows more significant load plateaus and a higher creep rate than mt-HNASS. Analysis reveals that higher hardness and larger m value of nt-HNASS arise from stronger strain hardening role, which is caused by the higher storage rate of dislocations and the interactions between dislocations and high density twins. The more significant load plateaus and higher creep rates of nt-HNASS are due to the rapid relaxation of the dislocation structures generated during loading.
