Abstract:The effect of yttrium and mischmetal(MMs) on the as-cast and solid solution treated structures of Mg-Al alloys with different Al-contents was investigated. The results show that the MMs in Mg-Al alloy existed in rod Al₄(Ce, La)compound while Y in Mg-Al alloy in polygonal Al₂Y compound. The amount of Mg₁₇Al₁₂ in Mg-Al alloy is decreased with increasing Y or MMs addition, and Mg₁₇Al₁₂  intermetallic compound is changed from continuous network to discontinuous one. The Al₄(Ce, La) and Al₂Y compounds are not dissolved into Mg-Al alloy matrix during solid solution treatment so that their high heat stability can be exhibited. The experiment of mechanical properties indicate that elongation and impact toughness of the Mg-Al-Y alloy with polygonal Al₂Y compound are higher than those of Mg-Al-MMs alloy with rod Al₄(Ce, La) compound

Key words: alloy; yttrium and mischmetal; Mg-Al structure and property; microprobe