The effect of the rare earth element Er on the microstructures and properties of Mg-Al intermetallic were studied in this experiment. Metallographic and X-ray diffraction（XRD） results showed that the microstructures of Mg-Al-Er alloys varied with Er content. The Mg-44Al-0.5Er and Mg-43.8Al-1.0Er alloys were both composed of Mg17Al12 matrix and Al3 Er phase, whereas Mg-43Al-3.0Er and Mg-42Al-5.0Er were composed of Mg17Al12 matrix, Al3 Er phase, and Mg-Mg17Al12 eutectic. The Mg-42Al-5.0Er alloy showed the highest microhardness, and the values remained nearly stable as Er content increased from 1.0 wt.% to 5.0 wt.%. The dispersed second phase Al3 Er caused the grain refinement of the Mg-Al-Er alloy, which was the main reason for the improvement in microhardness. The corrosion resistance of the Er-containing alloys initially increased and then decreased with increasing Er content. All the Er-containing alloys had the ability to suppress hydrogen evolution, which was the main reason for the higher corrosion resistance of the modified alloys than that of the Mg-44.3Al alloy. Considering the higher hardness and dispersity of the Al3 Er phase, Mg-43.8Al-1.0Er exhibited higher wear resistance than the as-cast Mg-44.3Al alloy.
In order to increase the depth or concentration of Ti ion implantation of pure iron, the surface mechanical attrition treatment(SMAT), which can fabricate a nanometer-grained surface layer without porosity and contamination in a pure iron plate, was used before ion implantation. Ti ion was implanted into the SMA treated sample and coarse-grained counterpart by using a metal vapor vacuum arc source implanter. The changing of depth and concentration of Ti was studied in a function of implantation time.By optical microscopy, transmission electron microscopy and X-ray diffraction, the grain size of the nano structured surface was studied. Micro-hardness, friction and wear behavior of nano surface layers were studied. By energy dispersive X-ray spectroscopy and Auger electron spectroscopy, the chemical composition and concentration of Ti ion in the surface implantation layer were studied. Experimental results showed that the concentration of Ti increased dramatically compared with untreated coarsegrained samples, which is attributed to the existence of higher density of defects(supersaturated vacancies, dislocations, non-equilibrium grain boundaries etc.) and compression stress field in the SMA treated nanocrystallined surface layer. The interaction between the defects and the implanted solute atoms leads to the increment of solid solubility. But the implantation depth showed inconspicuous change. It is shown that the ion range is just relevant to the energy and mass of the ion, dose of injection,the mass and density of target material.
Xu LiYanli AnYinghui WeiHuayun DuLifeng HouChunli GuoHongbo QuYide Wang
