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

对GH4738合金在热加工过程中不同阶段的MC、M_(23)C_(6)、γ′相3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M_(23)C_(6)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。

MC,M_(23)C_(6),andγ′precipitates of GH4738 superalloy at different stages during hot working were studied.Behavior of precipitates in different stages of hot working was investigated:(1)the main precipitates in the superalloy billet are primary MC carbides and primaryγ′phase;(2)after hot deformation,the primary MC carbides are partially decomposed,and the nano-sized intragranular secondary MC carbides as well as a small number of grain boundary secondary M_(23)C_(6) carbides and secondaryγ′phase are precipitated;(3)after heat treatment,the primary MC carbides are further decomposed until complete dissolution,and then the nanocrystalline secondary MC carbides are transformed into many bottle-shaped secondary M23C6 carbides.Meanwhile,γ′phase basically achieves the complete precipitation,but it grows slightly.