Abstract
Mg-Gd-Y-Zn-Zr Mg alloys show excellent performance in high-end manufacturing due to its strength, hardness and corrosion resistance. However, the hot deformation and dynamic recrystallization (DRX) behaviors of Mg-13.5Gd-3.2Y-2.3Zn-0.5Zr were not studied. For this article, hot compression behavior of homogenized high rare-earth (RE) content Mg-13.5Gd-3.2Y-2.3Zn-0.5Zr (wt%) alloy was investigated by using the Gleeble-3500D thermo-simulation test machine under the temperature of 350–500 °C and the strain rate of 0.001–1 s−1. It was found that the high flow stress corresponded to the low temperature and high strain rate, which showed DRX steady state curve during the hot compression. The hot deformation average activation was 263.17 kJ/mol, which was obtained by the analysis of the hyperbolic constitutive equation and the Zener-Hollomon parameter. From observation of the microstructure, it was found that kink deformation of long period stacking ordered (LPSO) phase was one of the important coordination mechanisms of hot deformation at low temperature. The processing map with the strain of 0.5 was established under the basis of dynamic material model (DMM); it described two high power dissipation domains: one appearing in the temperature range of 370–440 °C and the strain rate range of 0.001–0.006 s−1, the other appearing in the temperature range of 465–500 °C and strain rate range of 0.001–0.05 s−1, in which dynamic recrystallization (DRX) mainly ocurred. The highest degree of DRX was 18% from the observation of the metallographic.
Highlights
The requirements of lightweight structure and energy saving make magnesium alloy become the material selection direction of many important structural parts at present; the restriction of poor mechanical properties, especially the high temperature performance, affect the development of traditional magnesium alloys [1,2,3].The alloys of Mg-Gd-Y system, which is famous for its low density, good corrosion resistance and excellent performance at both ambient temperature and elevated temperature, received more and more attention in automobile applications [4,5]
The hot deformation behavior of homogenized Mg-13.5Gd-3.2Y-2.3Zn-0.5Zr alloy via hot compression tests has been studied at the temperature from 350 ◦ C to 500 ◦ C and the strain rate range of 0.001–1 s−1
The flow stress increases with the decrease of temperature and the increase of strain rate
Summary
The requirements of lightweight structure and energy saving make magnesium alloy become the material selection direction of many important structural parts at present; the restriction of poor mechanical properties, especially the high temperature performance, affect the development of traditional magnesium alloys [1,2,3].The alloys of Mg-Gd-Y system, which is famous for its low density, good corrosion resistance and excellent performance at both ambient temperature and elevated temperature, received more and more attention in automobile applications [4,5]. Drits et al developed a variety of high performance rare-earth (RE) magnesium alloys such as WE54 (Mg-5Y-1.5Nd-1.5HRE-0.5Zr), Materials 2018, 11, 2282; doi:10.3390/ma11112282 www.mdpi.com/journal/materials. Rokhlin et al found that some rare-earth elements (Gd, Dy, Tb, etc.) had greater solid solubility than Y in magnesium, and the alloy exhibited better elevated mechanical properties than WE54 alloy when the content of Gd reached 10% [7,8]. With the deepening of research, it was found that the addition of the Zn element can generate a special stacking ordered structure called LPSO phase, and the properties can be greatly improved by controlling the type and distribution of LPSO phases [9,10,11]. It was believed that the LPSO structure can rise the critical shear stress (CRSS) of the slip system on the basal planes and improve the sliding of non-basal planes
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