open access

https://hdl.handle.net/2115/75126

Formation of LPSO Phases in As-Cast Mg-Al-Zn-Gd Quaternary Alloys

日本語

formation type

2019-08-01

日本金属学会

Journal of the Japan Institute of Metals and Materials

83(8)

257-263

Mg alloys with long period stacking ordered (LPSO) phases are categorized into two types. Mg alloys where the LPSO phase forms in as-cast state are categorized as Type I, while those where the LPSO phase does not appear in as-cast state but forms during heat treatment are categorized as Type II. However, the origin of the formation type of Mg alloys with LPSO phases still remains poorly understood. In the present study, three different Mg85(Al, Zn)6Gd9 quaternary alloys were prepared to elucidate the dominant factors that determine the formation type of Mg alloys with LPSO phases. The α-Mg, Al2Gd, Mg3Gd and LPSO phases were characterized in the as-cast quaternary alloys by microstructural observation, composition analysis and crystal structure analysis by using electron probe microanalysis and X-ray diffraction. It indicates that all the quaternary alloys are categorized as Type I even though the original two ternary Mg85Al6Gd9 and Mg85Zn6Gd9 alloys are categorized as Type II. The crystal structure of the LPSO phases observed in the as-cast alloys is considered to be 18R with dilute solute elements. The amount of the LPSO phases in the as-cast state increases with increasing the Zn content in the alloys. It is considered to be the cause of destabilization of the primary crystallized Al2Gd phase by the addition of Zn and hence relative stabilization of the LPSO phases. It is thus concluded that the relative phase stability in the vicinity of the LPSO phase is considered to be crucial for determination of the formation type of Mg alloys with LPSO phases.

学術雑誌論文

Version of Record

0021-4876

1880-6880

AN00062446