Acta Metallurgica Sinica (English Letters) ›› 2019, Vol. 32 ›› Issue (2): 178-186.DOI: 10.1007/s40195-018-0819-0

• Orginal Article • Previous Articles     Next Articles

Detailed Structures and Formation Mechanisms of Well-Known Al10RE2Mn7 Phase in Die-Cast Mg-4Al-4RE-0.3Mn Alloy

Qiang Yang1(), Shu-Hui Lv2, Fan-Zhi Meng2, Kai Guan1,4, Bai-Shun Li1,4, Xu-Hu Zhang3, Jing-Qi Zhang3, Xiao-Juan Liu1, Jian Meng1()   

  1. 1 State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
    2 School of Materials Science and Engineering, Changchun University of Science and Technology, Changchun 130022, China
    3 Aerospace Research Institute of Materials and Processing Technology, Beijing 100076, China
    4 University of Sciences and Technology of China, Hefei 230026, China
  • Received:2018-07-05 Revised:2018-08-14 Online:2019-09-19 Published:2019-02-13

Abstract:

The detailed structures and the corresponding formation mechanisms of the well-known Al10RE2Mn7 phase in the conventional die-cast Mg-4Al-4RE-0.3Mn alloy were thoroughly investigated using transmission electron microscopy (TEM). The results indicate that the Al10RE2Mn7 phase ordinarily contains both normal $(11\overline{2} 1)$ twins and orientation twins. Both detailed TEM observations and density functional theory calculations indicate that the Al10RE2Mn7 phase is transferred from the Al8REMn4 phase following an orientation relationship as $[010]_{{{\text{Al}}_{ 8} {\text{REMn}}_{ 4} }} / /[\overline{1} 101]_{{{\text{Al}}_{ 1 0} {\text{RE}}_{ 2} {\text{Mn}}_{ 7} }}$ and $(101)_{{{\text{Al}}_{ 8} {\text{REMn}}_{ 4} }} / /(11\overline{2} 0)_{{{\text{Al}}_{ 1 0} {\text{RE}}_{ 2} {\text{Mn}}_{ 7} }}$. Moreover, forming orientation twins in the Al10RE2Mn7 phase is attributed to the blurry regions at incoherent twin boundaries in the Al8REMn4 phase. Finally, these formed orientation twins result in the $(11\overline{2} 1)$ twins in the Al10RE2Mn7 phase.

Key words: Transmission electron microscopy, Phase transformation, Intermetallic phase, Twin boundary, Orientation relationship