High strength and ductility Mg-8Gd-3Y-0.5Zr alloy with bimodal structure and nano-precipitates

doi:10.1016/j.jmst.2019.10.024

Abstract

Abstract:

To resolve the strength-ductility trade-off problem for high-strength Mg alloys, we prepared a high performance Mg-8Gd-3Y-0.5 Zr (wt%) alloy with yield strength of 371 MPa, ultimate tensile strength of 419 MPa and elongation of 15.8%. The processing route involves extrusion, pre-deformation and aging, which leads to a bimodal structure and nano-precipitates. Back-stress originated from the deformation-incompatibility in the bimodal-structure alloy can improve ductility. In addition, dislocation density in coarse grains increased during the pre-deformation strain of 2%, and the dislocations in coarse grains can promote the formation of chain-like nano-precipitates during aging treatment. The chain-like nano-precipitates can act as barriers for dislocations slip and the existing mobile dislocations enable good ductility.

Key words: Magnesium alloy, Strength-ductility trade-off, Bimodal structure, Back-stress, Chain-like intragranular nano-precipitates

Xiaoxiao Wei, Li Jin, Fenghua Wang, Jing Li, Nan Ye, Zhenyan Zhang, Jie Dong. High strength and ductility Mg-8Gd-3Y-0.5Zr alloy with bimodal structure and nano-precipitates[J]. J. Mater. Sci. Technol., 2020, 44: 19-23.

Figures/Tables 4

Fig. 1. (a) Engineering stress-strain curves of as-extruded and aged GW83 K Mg alloys at room temperature and (b) representative tensile properties of Mg-Gd-Y based alloys [[21], [22], [23], [24], [25], [26], [27], [28], [29], [30]].

Fig. 2. Optical micrograph (a) and EBSD results of as-extruded GW83 K Mg alloy: (b) inverse pole figure (IPF) map; (c) kernel average misorientation (KAM) map; (d) grain size distribution of DRXed grains. The extrusion direction is horizontal.

Fig. 3. Dislocation configuration in as-extruded and pre-deformed samples: (a, b) as-extruded; (c, d) pre-deformation strain of 2%; (e, g) pre-deformation strain of 8%, and in which (a, c, e) are in coarse grains, and (b, d, f, g) are in fine grains.

Fig. 4. HAADF-STEM images of precipitates in aged samples: (a-d) as-extruded; (e, f) pre-deformation strain of 2%; (g, h) pre-deformation strain of 8%, and in which (a, b, e, g) are in fine grains, and (c, d, f, h) are in coarse grains.

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