Study on the Microstructure and Property of Al-4.5Mg-0.7Mn-0.1Zr-Er

　　Study on the Microstructure and Property of Al-4.5Mg-0.7Mn-0.1Zr-Er
　　In this thesis, Al-4.5Mg-0.7Mn-0.1Zr alloy containing different percent of Er were prepared with Metallurgy cast processing. By means of hardness measurement , tensile properties measurement, optical microscopy(OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), effects of Er on microstructure and mechanical properties of Ball Neodymium Magnets Al-4.5Mg-0.7Mn-0.1Zr alloy under different states (as-cast, homogenize -ed, hot-rolled, cold-rolled, annealed) were investigated. The existing forms and interactions between Er and other alloying elements in Al-4.5Mg-0.7Mn-0.1Zr alloy, the strengthening and refining mechanism were profoundly studied, and the effects of Er on corrosion properties of Al-4.5Mg-0.7Mn-0.1Zr alloy were discussed.Research results show that the addition of different content Er was found to improve the mechanical properties (strength and hardness) of Al-4.5Mg-0.7Mn-0.1Zr alloy to different extent.
　　When Er additions were 0.4%, the strength was considerably improved for Al-4.5Mg-0.7Mn-0.1Zr alloy, while the ductility keeps stable or become better. With the increase of Er additions, the strength is hardly influenced and ductility decrease obviously. The primary strengthening mechanisms in Al-4.5Mg-0.7Mn-0.1Zr alloy added Er are fine grain strengthening, solubility strengthening and precipitation strengthening. Of all mentioned three strengthening mechanisms, the precipitation strengthening plays more important role than others.The refinement effect of Er on the microstructure of the as-cast Al-4.5Mg-0.7Mn -0.1Zr alloy became prominent gradually, and the http://www.chinamagnets.biz netlike structure was slowly refined, the dendritic distance and grain size were continually reduced with the increase of Er content. The grain will be refined significantly when Er additions are 0.4%wt or more. The grain fine mechanism is related with the primary Al3Er which was formed during solidification. These primaries (Al3Er) which match very closely to the Al matrix will be able to act as heterogeneous nucleates, so the nucleation ration is improved and the grain is refined.The formation enthalpy between Er and Mg & Er and Mn are lower that between Er and Al, so the existing forms of Er in Al-4.5Mg-0.7Mn-0.1Zr are quite similar to that in Al-5Mg alloy, that is to say, Er is resolved in Al matrix to form solid solution when its content is low (≤0.2%). If the content of Er is higher (≥0.4%), the