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通过对4种不同Hf含量(0~0.80%,质量分数,下同)的第二代镍基单晶高温合金DD11铸态及热处理态组织定量表征与1100℃,140 MPa持久性能测试,研究了Hf对相转变温度、(g+γ’)共晶组织、碳化物、微孔、凝固偏析、合金元素成分分配比及持久性能的影响.结果表明,添加Hf显著降低合金的固/液相线,降低微孔含量,提高铸态共晶组织体积分数、MC型碳化物含量以及凝固偏析程度.合金热处理后,随着Hf含量提高,固溶微孔含量显著降低、残余共晶和碳化物含量显著增加.添加Hf通过提高Re,Mo和Cr的成分分配比,增加γ/γ’错配度,减小γ/γ’界面位错间距,促进Re,Mo和Cr向γ相中偏聚,提高固溶强化效果,减小微孔含量等方式,显著提高DD11合金持久性能.但当Hf含量达到0.80%时,热处理后的残余共晶、碳化物含量较高,导致合金持久性能明显降低.
The four kinds of Hf content (0 ~ 0.80%, mass fraction, the same below) second-generation nickel base single crystal superalloy DD11 as-cast and heat-treated state quantitative characterization and 1100 ℃, 140 MPa durability test, Hf on the phase transformation temperature, (g + γ ’) eutectic structure, carbide, micropore, solidification segregation, alloying element composition distribution ratio and permanent property were studied.The results show that adding Hf significantly reduces the solid / liquidus , Decrease the content of micropores, increase the volume fraction of as-cast eutectic structure, the content of MC type carbides and the degree of solidification segregation.With the increase of Hf content, the content of solid solution micropores decreases remarkably, and the residual eutectic and carbide content Hf increased the segregation of Re, Mo and Cr to the γ phase by increasing the fractional distribution of Re, Mo and Cr, increasing the γ / γ mismatch, decreasing the interfacial dislocation spacing of γ / γ ’ Improve the solid solution strengthening effect and reduce the content of micropores, which can significantly improve the ductility of DD11 alloy.However, when the content of Hf reaches 0.80%, the residual eutectic and carbide content after heat treatment is higher, which leads to the significant decrease of the ductility of the alloy.