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Enhancing mechanical properties of Mg-Gd-Y-Zn alloys via microalloying with Ce and La
Zhaobin Zhang,Jonghyun Kim,Hongxin Liao,김기범,최태집,이태경,FuSheng Pan 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.9
This study investigated the microstructure and mechanical properties of Mg-1Gd-1Y-1Zn (at.%) alloys containing designed amounts of Ce or La. The Mg5(Gd,Zn) phase formed in the as-cast Mg-Gd-Y-Zn- Ce/La alloys and disappeared after a homogenization treatment at 500°C for 24 h. The addition of Ce and La resulted in the formation of Ce(Mg,Zn)12 and La(Mg,Zn)12 phases, respectively. Except for that, the Ce or La addition had no significant effect on the morphology, volume fraction, and type of the long-period stacking ordered (LPSO) phases in the Mg-Gd-Y-Zn alloy. The grain size decreased with increasing microalloying content because the heavy Ce and La atoms impeded atomic migration across the boundaries. The solute drag effect led to the formation of the rare earth texture in the extruded Mg-Gd-Y-Zn-Ce/La alloys, whose extent decreased with increasing microalloying content. The mechanical strength was improved by the addition of Ce or La at the sacrifice of ductility. In particular, La exhibited a stronger reinforcement ability than Ce when it was added to the Mg-Gd-Y-Zn alloys. Among the investigated chemical compositions, the Mg-1Gd-1Y-1Zn- 0.3La alloy exhibited the highest strength because it had the finest grains, the highest volume fraction of the second phase, and the weakest texture intensity. Furthermore, the alloys showed an unusual yield asymmetry due to the difference in the deformation mode of the LPSO phase.
Effect on Zn on Microstructures and Mechanical Properties of Mg–Gd–Y–Zn LPSO Alloys
Jonghyun Kim,Hongxin Liao,Xiang Ou,Zhaobin Zhang,Kaikai Kang,Taekyung Lee,Fusheng Pan 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.11
In this study, the microstructures and mechanical properties of Mg–1Gd–1Y–xZn alloys (x = 0.2, 0.4, 0.6, and 0.8) wereinvestigated. Microstructural evolution was tracked during the process of casting, homogenization, and extrusion. Long-periodstacking-ordered (LPSO) and β phases were formed in the as-cast alloys. The volume fraction of the LPSO phase increasedwith increasing Zn content, whereas that of the β phase decreased. Although the homogenization dissolved the β phase intothe Mg matrix, there was no significant change in the volume fraction of the LPSO phases. Increasing the Zn content led toa slight reduction in grain size and a simultaneous strengthening of texture. The Mg–1Gd–1Y–0.2Zn alloy possessed a highdensity of fine LPSO phases and excellent reinforcement capacity, thereby exhibiting excellent mechanical properties atroom temperature. In addition, the low volume fraction of the LPSO phases in this alloy led to suppressed yield asymmetry.