【摘要】 用光学显微镜、扫描电子显微镜、X射线衍射分析、差热分析等手段对低合金化τ型高锌镁合金ZA73的铸态显微组织和凝固特征进行研究。结果表明,金属型铸造ZA73合金的铸态组织由球状等轴-αMg枝晶和在晶界以及枝晶间均匀分布的Mg32(Al,Zn)49化合物组成。结合DSC分析结果和Mg-Zn-Al三元液相面投影图,给出了熔体凝固过程中发生的相变反应和凝固序列。与高合金化τ型高锌镁合金ZA104相比,由于Al、Zn元素含量的降低,ZA73合金具有较高的液相线温度和较宽的凝固温度区间,分别为627℃和283℃,而第二相相变起始温度则低于ZA104合金,约为354℃。更多还原

【Abstract】 The as-cast microstructure and solidification characteristics of a low-alloying τ-type Mg-Zn-Al based magnesium alloy with a nominal element content of 7wt%Zn and 3wt%Al（ZA73） have been experimentally examined using optical microscopy,scanning electron microscopy,X-ray diffraction,and differential scanning calorimetry analysis.The results show that the as-cast microstructure of permanent mould casting ZA73 magnesium alloy consists of α-Mg globular equiaxed dendrite with Mg₃₂（Al,Zn）₄₉ compounds as the only secondary phase homogenously distributed in interdendrite.Solidification sequence has been proposed with the help of DSC analysis and Mg-Zn-Al ternary liquidus projection phase diagram.Compared to ZA104 alloy containing larger amounts of alloying element,ZA73 alloy has higher liquidus temperature（～627℃）,wider solidification range（～283℃）,and lower starting temperature of the second phase transformation（～354℃） due to the decrease of its alloying element contents.更多还原