Effect of Y content on microstructure and mechanical properties of Mg-2·4Nd-0·2Zn-0·4Zr alloys

ISSN： 1743-2847

Source： Materials Science and Technology, Vol.29, Iss.2, 2013-02, pp. : 148-155

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Abstract

The effects of yttrium (0, 2·5, 4·0 and 6·0 wt-%) on the microstructures, age hardening behaviours and mechanical properties of the Mg-2·4Nd-0·2Zn-0·4Zr alloys were investigated. The results demonstrated that the Mg-2·4Nd-0·2Zn-0·4Zr alloy was mainly composed of -Mg and Mg₁₂Nd phases. When Y was the added into Mg-2·4Nd-0·2Zn-0·4Zr alloy, Mg₂₄Y₅ phases formed. The volume fraction of Mg₂₄Y₅ phases increased, and the grains were refined with the Y element increasing. Moreover, the additions of Y could improve the peak aged hardness and mechanical properties of the alloys. Mg-2·4Nd-0·2Zn-0·4Zr-6Y alloy exhibited the highest yield strength of 280 MPa in 225°C peak aged condition; Mg-2·4Nd-0·2Zn-0·4Zr-4·0Y alloy exhibited the optimal mechanical properties in the peak aged condition, whose value of ultimate tensile strength, yield strength and elongation were 330 MPa, 265 MPa and 6·5% respectively. The optimal mechanical properties of Mg-2·4Nd-0·2Zn-0·4Zr-4·0Y alloy were mainly attributed to the high volume fraction of fine metastable β′ precipitates in the matrix and the discontinuous distribution of the sparse grain boundary precipitates along grain boundary.