Investigation on the formation of central damage in cross wedge rolling of GH4169 alloy

Cross wedge rolling process provides a new way with short production chain and precise control for high-performance blade preforming used in aeroengine, but the issue of central damage needs to be paid attention and investigated. Therefore, this paper aims to understand the formation mechanism of central damage on CWR of GH4169 alloy. The uniaxial hot tensile test and CWR experiments were carried out to explore the high-temperature deformation behavior of GH4169 alloy, as well as the central damage of GH4169 alloy CWR process. Moreover, the finite element model was established and used to analyze the evolution of stress and strain at different position. The results showed that central part of the workpiece is in the state of higher stress triaxiality η , which is easy to cause damage. And the micro-holes in the center of workpiece mainly nucleated around the detached NbC carbide. Meanwhile, the first principal stress σ_1 and the maximum shear stress τ_max are the dominant factors which affect the central damage. Therefore, a novel damage criterion suitable for CWR of GH4169 alloy was developed with considering the effect of stress triaxiality η and the sensitivities of deformation temperature and strain rate on the central damage evolution. In addition, initial forming temperature T 0 is the most important factor affecting the central damage, and the maximum area reduction φ and rolling speed n are related to the initial deformation temperature T 0 . And in order to inhibit the damage, the initial forming temperature should be controlled below 1020℃, and the area reduction and rolling speed should not be higher than 55