Obtaining Ultra-High Strength and Ductility in a Mg-Gd-Er-Zn-Zr Alloy via Extrusion, Pre-deformation and Two-Stage Aging

doi:10.1007/s40195-020-01132-x

Abstract

Abstract:

The Mg-12Gd-1Er-1Zn-0.9Zr (wt%) alloy with ultra-high strength and ductility was developed via hot extrusion combined with pre-deformation and two-stage aging treatment. The age-hardening behavior and microstructure evolution were investigated. Pre-deformation introduced a large number of dislocations, resulting in strain hardening and higher precipitation strengthening in the subsequent two-stage aging. As a result, the alloy showed a superior strength-ductility balance with a yield strength of 506 MPa, an ultimate tensile strength of 549 MPa and an elongation of 8.2% at room temperature. The finer and denser β′ precipitates significantly enhanced the strength, and the bimodal structure, small β-Mg₅RE phase as well as dense γ′ precipitates ensured the good ductility of the alloy. It is suggested that the combination of pre-deformation and two-stage aging treatment is an effective method to further improve the mechanical properties of wrought Mg alloys.

Key words: Magnesium alloys, Pre-deformation, Two-stage aging, Precipitation strengthening, Mechanical properties

Lin-Yue Jia, Wen-Bo Du, Jin-Long Fu, Zhao-Hui Wang, Ke Liu, Shu-Bo Li, Xian Du. Obtaining Ultra-High Strength and Ductility in a Mg-Gd-Er-Zn-Zr Alloy via Extrusion, Pre-deformation and Two-Stage Aging[J]. Acta Metallurgica Sinica (English Letters), 2021, 34(1): 39-44.

Figures/Tables 4

Fig. 1 a Age-hardening behavior of the E and EPD samples, b tensile engineering stress-strain curves of the various samples

Fig. 2 EBSD results and corresponding pole figures (tested by XRD) of a-c E + TSA , d-f EPD + TSA samples: a, d IPF maps, b, e line profiles of the misorientation angle along the black arrow in a, d, c, f (0002) pole figures

Fig. 3 TEM observations of the a EPD, b E + TSA , c, d EPD + TSA samples: b-d TEM images and corresponding SAED patterns taken from the precipitates inside DRXed grains along [0001]α-Mg

Fig. 4 TEM observations of the EPD + TSA sample: a BF image of the dynamic precipitates, b HAADF-STEM micrograph and corresponding SAED pattern taken from the precipitates inside worked grains along [11$\overline{2}$0]α-Mg, c mapping of Gd, Er and Zn elements in the boxed region in b

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