Cu含量对K4061合金显微组织和拉伸性能的影响

Effects of Cu Content on the Microstructure and Tensile Property of K4061 Alloy

随着我国液氧煤油火箭发动机推力的不断提高,亟需一种强度更高、抗富氧燃烧性能更好的新型高温合金材料。K4061合金属于第二代抗富氧烧蚀高温合金,与第一代抗富氧烧蚀高温合金相比,合金成分的显著特点是添加了Cu元素。但是,目前关于Cu在高温合金中的作用机制研究较少。因此,本工作在热力学相平衡计算的基础上,结合DSC、SEM以及TEM实验,研究了添加(1%~10%)Cu(质量分数)对K4061合金析出相以及Cu元素分布的影响。热力学计算结果表明,K4061合金在平衡凝固过程中,首先从液相中析出γ基体,随着液相溶质元素成分逐步提高,在凝固末期又从液相中析出MC型碳化物。此外,Cu的添加对于K4061合金的平衡凝固路径没有显著影响,但会降低K4061合金的固/液相线温度和MC的析出温度。实验结果表明,与平衡凝固不同,在K4061合金的实际凝固过程中,除了γ基体和MC型碳化物之外,在凝固末期还会析出δ相。不同Cu含量的K4061合金中析出相种类并未改变,这与热力学计算结果一致,但是在添加Cu的K4061合金中未观察到富Cu相并且Cu元素也没有偏聚到晶界或者碳化物相中。TEM观察结果表明,Cu富集在强化相内,且会增大强化相尺寸。此外,Cu的添加会降低合金的室温和750℃高温抗拉强度。

The LOX(liquid oxygen)/kerosene rocket engine is widely used in heavy launch vehicles owing to its low cost,high performance,and high reliability.However,the next-generation LOX/kerosene rocket engine requires a new superalloy that can resist oxygen-rich combustion.The K4061 alloy is a second-generation superalloy that has better resistance to oxygen-rich combustion compared to the firstgeneration superalloy due to the addition of the Cu element in its composition.However,there is limited research on the role of the Cu element in the superalloy.This study investigates the effect of Cu content(mass fraction)ranging from 1%to 10%on the microstructure and Cu distribution of K4061 alloy using thermodynamic calculations along with DSC,SEM,and TEM experiments.The results show that during the equilibrium solidification of K4061 alloy,theγmatrix precipitates first,followed by precipitating MC carbides at the end of solidification.The addition of Cu does not affect the equilibrium solidification path of the alloy;however,it lowers the solidus and liquidus temperatures of the alloy and the precipitation temperature of MC.During the nonequilibrium solidification,theδphase is also precipitated at the late solidification stage.The types of precipitated phases of K4061 alloy with different Cu contents remain unchanged,consistent with thermodynamic calculations.However,Cu-rich phases are not found in the sample,and Cu does not dissolve in MC in large quantities or segregate into grain boundaries.TEM results show that Cu is enriched in the strengthening phases,and the size of the strengthening phases slightly increases with the addition of Cu during aging heat treatment.Additionally,the addition of Cu reduced the room temperature and 750°C tensile strength of the alloy.