Evolution of LPSO phase and properties of Mg-Y-Gd-Zn-Zr alloy at different aging temperatures

doi:10.13251/j.issn.0254-6051.2024.09.016

Abstract

Abstract: The microstructural evolution of the Mg-6Y-3Gd-3Zn-0.5Zr alloys in the as-cast, solid solution and aging states and its influence on the mechanical properties were investigated by using OM, SEM, XRD, TEM and property testing methods. The results show that the as-cast alloy consists of dendritic α-Mg matrix with a continuous network of 18R-LPSO and Mg₂₄(Gd, Y, Zn)₅ mixed phases at the grain boundaries. After solid solution treatment, the most of Mg₂₄(Gd, Y, Zn)₅ phase and part of the 18R-LPSO phase are dissolved back into the matrix. A large amount of lamellar 14H-LPSO and Mg₃(Y, Gd) and Mg₅(Y, Gd) phases are precipitated in the matrix after aging at 250 ℃ and 300 ℃. Only 14H-LPSO phase is precipitated in the crystals after aging at 400 ℃. The tensile strength and elongation of the as-cast alloy are 222.7 MPa and 4.1%, respectively. The strength of the alloy decreases and the elongation increases slightly after aging. The alloy peak aged at 400 ℃ shows the greatest decrease in strength due to the large number and size of 14H-LPSO precipitated in the crystals, and the tensile strength decreases by 39 MPa compared with that of the as-cast state.

Key words: Mg-Y-Gd-Zn-Zr alloy, LPSO phase, heat treatment, mechanical properties

CLC Number:

TG156.92

Ren Guangxiao, Wang Chao, Cao Xijuan, Wang Kai, Wang Hongxia, Cheng Weili, Niu Xiaofeng. Evolution of LPSO phase and properties of Mg-Y-Gd-Zn-Zr alloy at different aging temperatures[J]. Heat Treatment of Metals, 2024, 49(9): 96-102.

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