The formation of quasicrystals and related approximant crystalline phases is studied in the Mg-Al-Zn alloy system by applying mechanical alloying technique. This technique is advantageous over the conventional melt-spinning because of the ease in sample preparation involving only the solid-state reaction. The quasicrystal is formed over a wide composition range. Those formed along the Bergman line corresponding to Mg39.5(All-xZnx)60.5 are found to be metastable and to transform into stable (1/1-1/1-1/1) Frank-Kasper phase by evolving the exothermic peak in the DSC run. Its stability is found to increase with decreasing Al content. On the other hand, those formed in the Mg-rich and 12-15 at.%Al region off the Bergman line are found to transform into the (2/1-2/1-2/1) approximant phase at temperatures exceeding 400°C, which accompanies the endothermic peak in the DSC run. The peritectic reaction is suggested to be involved. The most stable quasicrystal obtained in this experiment is Mg47.5Al15.0Zn37.5
