The influences of Al on the microstructural evolution and creep properties of Elektron21 processed by high shearing dispersion techniqueThursday (07.11.2019) 09:35 - 09:55 Part of:
The influences of 0.25% Al on the microstructural evolution and creep properties of Elektron21 alloy were investigated by high-energy X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In the casting process, a high shear dispersion technique (HSDT) was utilized to disperse the 0.25% Al uniformly in the matrix. Compressive creep tests were performed at 240 °C under a stress range of 80-140 MPa. With the addition of Al on Elektron21 by HSDT, its creep resistance was apparently increased by about one order of magnitude than that of Al-free Elektron21.The experimental results show that the addition of Al on Elektron21 using HSDT results in the grain coarsening from 80.1±5.0 to 167.0±5.7 µm. The grain morphology also transformed from equiaxed grains to typical dendrites. Moreover, the morphology of the intermetallics changed from network to compact dendrites and its dendrite arm spacing of primary α-Mg was refined. Al-Zr compound was observed in Al-containing Elektron21 changing from Al2Zr3 to Al2Zr phase and an additional phase Al2Nd occurred owing to the assistance of HSDT. The enhancement on the creep resistance of Elektron21 by HSDT results from the compact dendritic structure of intermetallics in the α-Mg to inhibit the dislocation movement during creep. Besides, HSDT leads to a relative homogeneous distribution of Al2Zr phase and promotes the occurrence of Al2Nd with a high thermal stability, which may play as efficient barriers to hinder the dislocation gliding and therefore improve the creep properties.