Mg-4Zn-1Mn镁合金均匀化热处理及导热率

采用光学显微镜、X射线衍射、布氏硬度测试、扫描电镜、能谱分析等方法,研究新型Mg-4Zn-1Mn(ZM41)镁合金在铸态和不同热处理状态下的显微组织、成分、硬度变化规律。用激光闪射法测定其不同状态的热扩散系数,计算得到导热率值。以空位扩散机制为基础,研究均匀化扩散动力学过程,建立此合金的均匀化扩散方程。结果表明:铸态组织枝晶偏析严重,晶界上有许多粗大的Mg7Zn3非平衡结晶相,Mn以单质形式存在于合金中。经370℃×12 h均匀化热处理后,大部分的Mg7Zn3相已溶入基体。根据实验结果和均匀化动力学计算,确定最佳均匀化处理工艺为370℃×12 h。该合金室温导热率值为125.5 W/(m.K),比常见的镁合金如AZ系、AM系、AS系等的导热性能高出1倍左右。

Homogenizing heat treatment and thermal conductivity of Mg-4Zn-1Mn magnesium alloy

Microstructure,composition and micro-hardness of as-cast and homogenized Mg-4Zn-1Mn(ZM41)magnesium alloy were investigated by means of optical microscopy,X-ray diffraction,hardness measurement,scanning electron microscopy and energy dispersive spectrometry.The thermal diffusivity was measured by the laser flash method and the thermal conductivity was calculated.Based on vacancy diffusion mechanism,the diffusion kinetics during the homogenizing heat treatment was investigated.The results indicate that serious dendrite segregation exists in the as-cast ZM41 magnesium alloy,and numerous coarse unequilibrium eutectic Mg7Zn3 phases are observed at grain boundaries.Mn element distributes mainly as pure Mn particles.Most of the Mg7Zn3 are dissolved after the alloy is homogenized at 370 ℃ for 12 h.On the basis of the experiment results and diffusion kinetics calculation,the proper parameters of the alloy for homogenizing heat treatment is heating at 370 ℃ for 12 h.Thermal conductivity of the ZM41 magnesium alloy at room temperature is 125 W/(m·K),almost twice as high as the other commercial magnesium alloys such as AZ series,AM series and AS series etc.