Preparation, Microstructure Evolutions, and Mechanical Property of an Ultra-Fine Grained Mg-10Gd-4Y-1.5Zn-0.5Zr Alloy

Huan Liu,Jingli Yan,Jinghua Jiang,Aibin Ma,Jiapeng Sun,Jia Ju,Jing Bai,Dan Song

doi:10.3390/met7100398

Huan Liu, Jingli Yan + Show 6 more

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https://doi.org/10.3390/met7100398

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Abstract

In this work, the microstructural evolutions and mechanical properties of an as-cast Mg-10Gd-4Y-1.5Zn-0.5Zr (wt %) alloy during successive multi-pass equal channel angular pressing (ECAP) were systematically investigated by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and compression test. The obtained results show that the microstructure of as-cast alloy consists of α-Mg grains, Mg3Gd island phase, few Y-rich particles, and lamellar 14H LPSO (long period stacking ordered) phase located at the grain boundaries. During ECAP, the Mg3Gd-type phase is crushed and refined gradually. However, the refined Mg3Gd particles are not distributed uniformly in the matrix, but still aggregated at the interdendritic area. The 14H phase becomes kinked during the early passes of ECAP and then broken at the kinking bands with more severe deformation. Dynamic recrystallization of α-Mg is activated during ECAP, and their average diameter decreases to around 1 μm, which is stabilized in spite of increasing ECAP passes. Moreover, nano-scale γ′ phases were dynamically precipitated in 16p ECAP alloy. Compression tests indicate that 16p ECAP alloy exhibits excellent mechanical property with compressive strength of 548 MPa and fracture strain of 19.1%. The significant improvement for both strength and ductility of deformed alloy could be ascribed to dynamic recrystallization (DRX) grains, refined Mg3Gd-type and 14H particles, and dynamically precipitated γ′ plates.

Highlights

In recent years, with the increasing demands for light-weighting in the aerospace, high speed train, and automobile industries, magnesium and its alloys have received much attention due to their low density, high specific strength, and excellent damping capacities [1,2]
The schematic diagram for this RD-equal channel angular pressing (ECAP) processing is listed in Figure 1, and it is apparent that multi-pass ECAP could be achieved by rotating the ECAP die without taking the sample out each pass [26]
Alloypattern of as-cast alloy, and three phases are indexed from the Figure 2 shows the XRD

Summary

Introduction

With the increasing demands for light-weighting in the aerospace, high speed train, and automobile industries, magnesium and its alloys have received much attention due to their low density, high specific strength, and excellent damping capacities [1,2]. Their inherent strengths are relatively lower when compared with steel and aluminum alloys, and lots of effort still need to be made to improve their strengths for broader applications [3,4]. By adding Zn and HRE elements simultaneously, a kind of novel long period stacking ordered (LPSO) structure is formed, which exhibits an extraordinary strengthening effect, especially in hot extruded or rolled Mg-RE-Zn alloys [10,11,12]

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