利用显微硬度、XRD及TEM分析了Mg-1.9Zn (原子分数, %)二元合金时效硬化现象及GP区的形态和出现的温度范围. 研究结果表明: 在343和383 K时效过程中, 过饱和固溶体中发生Zn原子偏聚, 形成形态不同的GP区; 在423 K时效, 硬化峰值出现较早, 没有典型GP区出现. 利用本文优化获取的镁基固溶体相的热力学参数, 给出镁基过饱和固溶体存在亚稳态溶解度间隙和溶质原子偏聚GP区时Gibbs自由能曲线的特征形式, 确定了具有GP区析出效应的Mg-Zn体系的合金成分范围和时效温度区间.
The age--hardening behavior of the Mg-1.9Zn (atomic fraction, %) alloy, morphologies of GP zones and temperature range of GP zone precipitation in the alloy were investigated by micro-hardness, XRD and TEM. The results show that the Zn atoms segregation occurs in the super-saturated solid solution, forming GP zones with different shapes during ageing process at 343 and 383 K; while at 423 K the age-hardening peak occurs earlier but no typical GP zone appeared. Using the thermodynamic parameters of the Mg-Zn system, the Gibbs free energy relations of the Mg-based solid solution phase were calculated, indicating the existences of the metastable miscibility gap and the solute atoms segregation in the super-saturated solid solution. With the reported data and the present experimental results, the ranges of composition and aging temperature for GP zone precipitation in the Mg-Zn alloy were determined.
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