组织特征对GH4151合金冲击性能的影响

Effect of Microstructure Characteristics on Impact Toughness of GH4151 Alloy

摘要:

采用示波冲击实验对不同热处理后的GH4151合金样品进行了测试，并结合金相显微镜、扫描电镜、透射电镜和相图计算等系统分析了组织特征及晶界特征对GH4151合金冲击韧性的影响。结果表明，随着固溶温度的升高，GH4151合金的一次γ′相含量逐渐降低，平均晶粒尺寸逐渐增大，仅固溶态合金的冲击韧性也逐渐增大。JMatPro相图计算显示，晶界会存在一定量的μ相（TCP相）和M₂₃C₆相。对示波冲击曲线和断口分析后发现，仅固溶处理的合金，其弹性变形功E_e、塑性变形功E_p和撕裂功E_c都较大，因此抵抗裂纹萌生及扩展的能力较好，冲击韧性较高；经固溶及两阶段时效处理后，其弹性变形功E_e和塑性变形功E_p均较小，撕裂功E_c甚至接近零，因此冲击韧性大幅降低。与仅固溶态相比，两阶段时效处理后合金冲击韧性大幅降低的主要原因是晶粒细化和时效过程中晶界μ相及M₂₃C₆相的协同析出，而与基体晶界特征关联性较小。

Abstract:

The GH4151 alloy samples after different heat treatments were tested using instrumented impact testing, and the effects of microstructural characteristics and grain boundary features on the impact toughness of GH4151 alloy were analyzed through metallographic microscope, scanning electron microscope, transmission electron microscope, and phase diagram calculations. The results show that the percentage of primary γ′ phase decreases with the increase in solid solution temperature, while the average grain size gradually increases and the impact toughness of the solution-treated alloy also gradually increases. The results of phase diagram calculation by JMatPro depict that there is a certain amount of μ phase (a type of TCP phase) at grain boundaries and M₂₃C₆. Analyses of the instrumented impact curves and fracture surfaces reveal that for the alloy subjected to solution treatment only, the elastic deformation work (E_e), plastic deformation work (E_p), and tearing work (E_c) are all relatively large, indicating a good resistance to crack initiation and propagation and a high impact toughness. After solution treatment followed by two-stage aging, both the E_e and E_p become significantly smaller, and the E_c even approaches zero, resulting in a substantial decrease in impact toughness. Compared with the sample subjected to solution treatment only, the significant reduction in impact toughness of sample after two-stage aging is primarily attributed to grain refinement and the synergistic precipitation of grain boundary μ phase and M₂₃C₆ carbides during aging, while showing relatively little correlation with the grain boundary characteristics of the matrix.