| Microstructural changes in rapidly solidified Mg-Al-Zn-Nd during heat treatment at 100℃, 250℃, 350℃ for 1hr and 24hrs have been investigated by using TEM, EDS, DSC, and X-ray diffraction analysis and hardness measurements. As-extruded Mg-Al-Zn-Nd consists of 1∼2㎛ size fine grains with the homogeneous distribution of 10∼50㎚ size Al₂Nd phase particles and 0.1∼0.3㎛ size quasicrystal-related particles. No microstructural changes occur during heat treatment at 100℃ and 250℃ for 1hr and 24hrs. After heat treatment at 350℃, the Al₂Nd phase particles are still stable, but the quasicrystal-related phase particles are replaced with Al_(11)Nd₃ phase particles. The amount of hardness decrease after heat treatment at 350℃ for 24hrs corresponds to only 10% of the hardness of as-extruded material, which suggests high thermal stability of rapidly solidified Mg-Al-Zn-Nd due to the relatively fine grain size and, particularly, the presence of thermally stable 50㎚ size Al₂Nd phase particles. |
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