组织特征对GH4151合金冲击性能的影响

Effects 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Ee、塑性变形功Ep和撕裂功Ec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Ee和塑性变形功Ep均较小，撕裂功Ec甚至接近零，因此冲击韧性大幅降低。与仅固溶态相比，双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:

Seiries oscilloscope impact tests were conducted for GH4151 alloy under different heat treatment parameters, then microstructure characteristics and grain boundary properties were investigated by using phase diegram calculation, precipitates and EBSD analysis by SEM and detailed phase structure determined by TEM, the relationship between microstructure evolution and impact toughness of GH4151 alloy was systematically studied. The results show that the percentage of primary γ′ phase gets lower with the inceasing of annealing solution temperature, while the average grain size gets greater. The JMat Pro results depict that for GH4151 alloy there exists a certain amount of μ phase, a type of TCP phase, at the grain boundary, besides the secondary carbides of M23C6. Oscilloscope impact tests show that the crack initiation energy including elastic deformation enegy and plastic deformation energy and the propagation enegy for annealing solutioned specimens were all greater than that of annealing aged ones, resulting the good resistance of crack initiation and propagation and good property of inpact toughness. and the impact toughness gets lower when the specimens were annealing aged due to the smaller crack initiation energy and propagation enegy. Further microstructure analysis by TEM shows that the tested impact toughness values were increased with the increase of average grain size and had little relationship with the properties of grain boundary. The main reasons that the sharp decrease of impact toughness for annealing aged specimens were the finer grain size and M23C6 carbides and μ phase precipitate at the grain boundary.