Microstructural evolution and mechanical properties of Mg–11Gd–4.5Y–1Nd–1.5Zn–0.5Zr alloy prepared via pre-ageing and hot extrusion

Abstract

The Mg-11Gd-4.5Y-1Nd-1.5Zn-0.5Zr (wt.%) alloy was pre-aged prior to hot extrusion.Pre-ageing treatment introduced uniform distribution of plate-like Mg 5 RE precipitates, which transformed into nano-scale globular Mg 5 RE particles by split and spheroidization during hot extrusion. These globular Mg 5 RE particles contributed to continuous dynamic recrystallization by promoting the evolution of low misorientation sub-grain boundaries to high misorientation grain boundaries and caused grain refinement through grain boundary pinning. The improved mechanical properties were ascribed to the grain refinement, globular Mg 5 RE and LPSO precipitates. The ratio of compressive to tensile yield strength is 1.2. The yield strength asymmetry was attributed to the deformation asymmetry of LPSO phase and non-isotropic deformation behaviours of Mg matrix in tension and compression.

On the microstructure and mechanical property of as-extruded Mg-Gd-Y-Zn alloy with Sr addition

“…7d). The plate phases are similar to previously reported Mg 5 RE phase [11,12], which is also confirmed by present EDS results. Thus, the bulk LPSO/Mg 17 Sr 2 phases, both in the micron size, and plate Mg 5 RE phases in nano-scale are found to precipitate in as-extruded sample 0.2Sr.…”

“…In the past decade, the Mg-Gd-Y-Zn based alloys containing long period stacking ordered (LPSO) structures have been shown to exhibit excellent mechanical properties, including the high tensile strength of over 500 MPa at room temperature [8][9][10][11][12]. The outstanding property can be…”

“…ascribed to the refinement of α-Mg matrix, precipitation of Mg-RE nano-particles, and formation of both strip LPSO phases within grain interiors and bulk LPSO phases along grain boundaries [11,12]. The strip LPSO phases with inter-distances of nano-meter scale can readily improve yield strength of Mg alloys via second phase strengthening mechanism of impeding dislocations movement in α-Mg matrix [3,13,14].…”

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

“…Moreover, it can be seen from the engineering stress-strain curves that the ECAP alloy in this work display strong work hardening effect, which suggests that the interaction between dislocations and microstructures (refined second phases, grain boundaries, and nano-precipitates) plays an important role in strengthening of the alloys [41]. The refined microstructures and increased phase boundaries or grain boundaries are effective to hinder the propagation of micro cracks, which obviously improves the toughness of the ECAP alloys.…”

High temperature mechanical behavior of an extruded Mg–11Gd–4.5Y–1Nd–1.5Zn–0.5Zr (wt%) alloy

“…2 revealed that Mg 3 RE and Mg 12 REZn phases co-existed in the cast-T4 sample. Based on the previous investigation, the LPSO phase can be identified as Mg 12 REZn [16]. The eutectic phase should be identified as Mg 3 RE or Mg 3 (RE, Zn) phase [17].…”