期刊
INTERNATIONAL JOURNAL OF MINERALS METALLURGY AND MATERIALS
卷 29, 期 8, 页码 1543-1550出版社
SPRINGER
DOI: 10.1007/s12613-021-2391-2
关键词
icosahedral quasicrystal; crystal structure; thermodynamic stability; Mg-Zn-Nd alloys
类别
资金
- National Natural Science Foundation of China [51871143, 11972219]
- Science and Technology Committee of Shanghai [19010500400]
- Shanghai Rising-Star Program [21QA1403200]
- Independent Research Project of State Key Laboratory of Mechanical Transmissions of China [SKLMT-ZZKT-2021M11]
In this study, the Mg40Zn55Nd5 icosahedral quasicrystal (I-phase) structure was observed in an as-cast Mg-58Zn-4Nd alloy using high-resolution electron microscopy. The thermodynamic stability of the quasicrystal was investigated and it was found to decompose into other phases after annealing.
The quasicrystal phase is beneficial to increasing the strength of magnesium alloys. However, its complicated structure and unclear phase relations impede the design of alloys with good mechanical properties. In this paper, the Mg40Zn55Nd5 icosahedral quasicrystal (I-phase) structure is discovered in an as-cast Mg-58Zn-4Nd alloy by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). A cloud-like morphology is observed with Mg41.6Zn55.0Nd3.4 composition. The selected area electronic diffraction (SAED) analysis shows that the icosahedral quasicrystal structure has 5-fold, 4-fold, 3-fold, and 2-fold symmetry zone axes. The thermodynamic stability of the icosahedral quasicrystal is investigated by differential scanning calorimetry (DSC) in the annealed alloys. When annealed above 300 degrees C, the Mg40Zn55Nd5 quasicrystal is found to decompose into a stable ternary phase Mg35Zn60Nd5, a binary phase MgZn, and alpha-Mg, suggesting that the quasicrystal is a metastable phase in the Mg-Zn-Nd system.
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