Formation of 14H-type long period stacking ordered structure in the as-cast and solid solution treated Mg–Gd–Zn–Zr alloys

• Published in: Journal of materials research 2009-05, Vol.24 (5), p.1842-1854
• Main Authors: Ding, W.J., Wu, Y.J., Peng, L.M., Zeng, X.Q., Yuan, G.Y., Lin, D.L.
• Format: Article
• Language: English
• Subjects: Applied and Technical Physics; Biomaterials; Inorganic Chemistry; Materials Engineering; Materials Science; Nanotechnology; Phase transformation; Second phases
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/jmr.2009.0215

The coherent fine lamellae consisting of the 2H-Mg and the 14H-type long period stacking ordered (LPSO) structure within α′-Mg matrix have been first observed in an as-cast Mg96.32Gd2.5Zn1Zr0.18 alloy. During subsequent solid solution heat treatment at 698–813 K, in addition to the lamellae within matrix, a novel lamellar X phase (Mg–8.37±1.0Zn–11.32±1.0Gd, at.%) with the 14H-type LPSO structure was transformed from the dendritical β phase, and a corresponding time–temperature–transformation (TTT) diagram was established. The 14H-type LPSO structure existing in Mg–Gd–Zn–Zr alloys derives from two variant means: the formation of LPSO structure within α′-Mg matrix and the transformation of the dendritical β phase to a lamellar X phase with the LPSO structure. The alloy solid solution treated at 773 K for 35 h exhibits higher tensile strength and better elongation than the nonheated alloy because of the lamellar X phase with the 14H-type LPSO structure and the 14H-type LPSO structure within matrix.