Li Ming, Yao Mengling, Liu Liangzhi, Zhang Xiaoxia, Xing Zhihui, Xia Xiangsheng, Liu Peng, Wan Yuanyuan, Chen Qiang, Wang Hongxia
Southwest Technology and Engineering Research Institute, Chongqing 400039, China.
Shanxi Key Laboratory of Advanced Magnesium Based Materials, School of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
Materials (Basel). 2024 Aug 16;17(16):4075. doi: 10.3390/ma17164075.
In this study, we prepared Mg-9Gd-2Nd-0.5Zr, referred to as alloy I, and Mg-9Gd-2Nd-1.5Zn-0.5Zr, referred to as alloy II. The effects of a long-period stacking ordered (LPSO) phase induced by Zn addition on the high-temperature mechanical properties and fracture morphology of alloy I and alloy II at different temperatures (25 °C, 200 °C, 225 °C, and 250 °C) were studied using optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results indicate that MgRE at the crystal boundary of the as-cast alloy I transformed into (MgZn)RE (as-cast alloy II) by the addition of Zn. After solid solution treatment, the secondary phase in alloy I completely disappeared, and there were still residual secondary phases in block-like and needle-like structures in alloy II, while layered LPSO phases precipitated in the matrix. During the high-temperature tensile test, the yield and tensile strength of alloy I decreased significantly with the increase in temperature, while the elongation increased. Compared to alloy I, the yield strength of alloy II with an LPSO phase showed an increasing trend at 25 °C~200 °C and then decreased when the temperature reached around 250 °C. The thermal stability was significantly enhanced, and the elongation was also higher than that of alloy I. As the temperature increased, the fracture surface of alloy I showed increased folding, bending of scratches, and crack enlargement. However, the fracture surface of alloy II remained largely unchanged, with only minor wrinkles and cracks appearing at temperatures reaching 250 °C.
在本研究中，我们制备了Mg-9Gd-2Nd-0.5Zr（称为合金I）和Mg-9Gd-2Nd-1.5Zn-0.5Zr（称为合金II）。采用光学显微镜（OM）、扫描电子显微镜（SEM）、能谱仪（EDS）、电子背散射衍射（EBSD）和透射电子显微镜（TEM）研究了添加Zn诱导的长周期有序堆积（LPSO）相对合金I和合金II在不同温度（25℃、200℃、225℃和250℃）下的高温力学性能和断口形貌的影响。结果表明，铸态合金I晶界处的MgRE通过添加Zn转变为（MgZn）RE（铸态合金II）。固溶处理后，合金I中的第二相完全消失，合金II中仍存在块状和针状结构的残余第二相，同时基体中析出层状LPSO相。在高温拉伸试验中，合金I的屈服强度和抗拉强度随温度升高而显著降低，伸长率增加。与合金I相比，具有LPSO相的合金II的屈服强度在25℃至200℃时呈上升趋势，但当温度达到250℃左右时下降。热稳定性显著提高，伸长率也高于合金I。随着温度升高，合金I的断口表面折叠增加、划痕弯曲和裂纹扩大。然而，合金II的断口表面基本保持不变，仅在温度达到250℃时出现轻微褶皱和裂纹。
