Effect of Trace Element Er on Al-Mg and Al-Mg-Mn Alloys

Abstract

The behaviors of trace element Er on binary Al-Mg and ternary Al-Mg-Mn alloys have been investigated through optical microscopy, x-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy and transmission electron microscope. It was found that Er additions more than 0.4% (wt%) produced a remarkable refinement in grain size of Al-Mg and Al-Mg-Mn alloys castings. Er can enhance the tensile strength of the two group experimental alloys significantly but not greatly decrease the elongation due to the formation of many fine like spherical and dispersive primary and precipitation Al3Er particles during casting and heating process. Al3Er particles have L12 crystal structure (space group Pm3m) with a lattice parameter of 0.42119nm, and have a coherent relationship with the matrix phase α-Al (mismatch only 4.1%), which can be acted as the heterogeneous nucleus during solidification to increase the rate of nucleation, and the other hands it can strongly pin up dislocations and subgrain boundaries and retard the recrystallization of alloys.