热加工过程中Ni基变形高温合金析出相的演变规律

Evolution of precipitates in Ni-based wrought superalloys during hot working

摘要:

变形高温合金在热加工过程中的相析出行为是影响合金抗拉强度的重要因素之一。本实验对GH4738合金在热加工过程中不同阶段的 MC，M23C6，γ′相三种析出相进行跟踪研究。析出相在热加工过程中不同阶段的表现：（1）合金坯料中的主要析出相为初生MC碳化物和初生γ′相。（2）合金经热变形后，初生MC碳化物发生部分分解并析出纳米级晶内次生MC碳化物和少量晶界次生M23C6碳化物，同时析出次生γ′相。（3）合金经热处理后，初生MC碳化物进一步分解直至完全溶解，进而纳米级晶内次生MC碳化物转变为大量酒瓶状晶内次级M23C6碳化物，同时γ′相接近于完全析出，但γ′相会有小幅度的长大。

Abstract:

During hot working, phase precipitation behavior is essential to deformed superalloys" tensile strength. This experiment tracked MC, M23C6, and γ′ precipitates of GH4738 superalloy at different stages during hot working. The behavior of precipitates in different stages of hot working: (1) The main precipitates in the superalloy billet were primary MC carbides and primary γ′. (2) After hot deformation, the primary MC carbides were partially decomposed and precipitated nano-sized intragranular secondary MC carbides and a small amount of grain boundary secondary M23C6 carbides and secondary γ′. (3) After heat treatment, the primary MC carbides were further decomposed until completely dissolved, and then the nanocrystalline secondary MC carbides were transformed into many bottle-shaped secondary M23C6 carbides. Meanwhile, γ′ was closed to complete precipitation, but γ′ the grew slightly.