Mechanism of Effects of Rare Earths on Microstructure and Properties at Elevated Temperatures of AZ91 Magnesium Alloy
来源期刊：JOURNAL OF RARE EARTHS2007年第3期
论文作者：Gao Ming Zhang Guoying Wei Dan Zhang Hui
Key words：electronic structure; alloying; grain boundary aggregation; microstructure and properties of magnesium alloy; rare earths;
Abstract: By using real-space recursion method, the energetics of the undoped and Al and/or RE atoms doped 7(1450)<0001> symmetric tilt grain boundaries (GBs) in AZ91 alloys were investigated. Similar calculations were performed on undoped and doped bulk α Mg for comparison. The results showed that Al atoms segregated at GBs in AZ91 alloys. When RE atoms were added, they also segregated at GBs, and their segregation is stronger than Al atoms′. Therefore, RE atoms retard the segregation of Al atoms. Calculations of interaction energy indicated that Al atoms repelled each other, and could form ordered phase with host Mg atoms. On the contrary to the case of Al, RE atoms attracted each other, they could not form ordered phase with Mg, but could form clusters. Between RE and Al, there existed attractive interaction, and this attractive interaction was the origin of Al11RE3 precipitation. Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.
Gao Ming1，Zhang Guoying1，Wei Dan1，Zhang Hui1
(1.College of Physical Science and Technoloy, Shenyang Normal University, Shenyang 110034, China)
Abstract:By using real-space recursion method, the energetics of the undoped and Al and/or RE atoms doped 7(1450)<0001> symmetric tilt grain boundaries (GBs) in AZ91 alloys were investigated. Similar calculations were performed on undoped and doped bulk α Mg for comparison. The results showed that Al atoms segregated at GBs in AZ91 alloys. When RE atoms were added, they also segregated at GBs, and their segregation is stronger than Al atoms′. Therefore, RE atoms retard the segregation of Al atoms. Calculations of interaction energy indicated that Al atoms repelled each other, and could form ordered phase with host Mg atoms. On the contrary to the case of Al, RE atoms attracted each other, they could not form ordered phase with Mg, but could form clusters. Between RE and Al, there existed attractive interaction, and this attractive interaction was the origin of Al11RE3 precipitation. Precipitation of Al11RE3 particles with high melting point and high thermal stability along GB improves high temperature properties of AZ91 alloys.
Key words:electronic structure; alloying; grain boundary aggregation; microstructure and properties of magnesium alloy; rare earths;
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