Liu Yunfang, Yang Yaqin, Yi Ming, Yu Jianmin, Li Baocheng, Zhang Zhimin
College of Materials Science and Engineering, North University of China, Taiyuan 030051, China.
Materials (Basel). 2021 Oct 2;14(19):5758. doi: 10.3390/ma14195758.
There is a new long-period stacking ordered structure in Mg-RE-Zn magnesium alloys, namely the LPSO phase, which can effectively improve the yield strength, elongation, and corrosion resistance of Mg alloys. According to different types of Mg-RE-Zn alloy systems, two transformation modes are involved in the heat treatment transformation process. The first is the alloy without LPSO phase in the as-cast alloy, and the MgRE phase changes to 14H-LPSO phase. The second is the alloy containing LPSO phase in the as-cast state, and the 14H-LPSO phase is obtained by the transformations of 6H, 18R, and 24R. The effects of different solution parameters on the second phase of Mg-9Gd-2Y-2Zn-0.5Zr alloy were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The precipitation mechanism of 14H-LPSO phase during solution treatment was further clarified. At a solution time of 13 h, the grain size increased rapidly initially and then decreased slightly with increasing solution temperature. The analysis of the volume fraction of the second phase and lattice constant showed that Gd and Y elements in the alloy precipitated from the matrix and formed 14H-LPSO phase after solution treatment at 490 °C for 13 h. At this time, the hardness of the alloy reached the maximum of 74.6 HV. After solution treatment at 500 °C for 13 h, the solid solution degree of the alloy increases, and the grain size and hardness of the alloy remain basically unchanged.
在Mg-RE-Zn镁合金中存在一种新的长周期堆垛有序结构，即LPSO相，它能有效提高镁合金的屈服强度、伸长率和耐腐蚀性。根据不同类型的Mg-RE-Zn合金体系，热处理转变过程涉及两种转变模式。第一种是铸态合金中无LPSO相，MgRE相转变为14H-LPSO相。第二种是铸态含LPSO相的合金，通过6H、18R和24R的转变获得14H-LPSO相。通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）和X射线衍射（XRD）研究了不同固溶参数对Mg-9Gd-2Y-2Zn-0.5Zr合金第二相的影响。进一步阐明了固溶处理过程中14H-LPSO相的析出机制。在固溶时间为13 h时，晶粒尺寸最初迅速增大，然后随着固溶温度的升高略有减小。第二相体积分数和晶格常数分析表明，合金中的Gd和Y元素从基体中析出，在490℃固溶处理13 h后形成14H-LPSO相。此时，合金硬度达到最大值74.6 HV。在500℃固溶处理13 h后，合金的固溶度增加，合金的晶粒尺寸和硬度基本保持不变。
