Effect of forged substrate geometry on temperature and stress field in additive manufacturing

Abstract The forming technology compounding forging and additive manufacturing (AM) is a new approach to fabricate partial structures by AM based on forged substrates. Such technology has great potential for improving material utilization and manufacturing efficiency. Using this technology, three three-dimensional transient-coupled thermomechanical finite element models were developed in this study. The models comprised single-pass multilayer walls deposited on three different types of forged substrates, i.e., with a groove, platform, and boss. The temperature and residual stress of the components were measured by an infrared camera and X-ray diffraction, respectively, and the simulated results were found to be consistent with the experimental results. Based on this, the effects of forged substrate geometry on the temperature field and stress field in the laser solid forming process of a Ti-6Al-4 V alloy were investigated. It was found that during the AM process, there was little difference in the molten pool maximum temperature and range of high temperature region for the components fabricated using AM based on forged substrates with different geometries. In addition, the temperature gradient decreased with an increasing number of deposited layers. The component fabricated with a groove had the largest temperature gradient in the early depositional stage, whereas the component with a platform had the lowest residual tensile stress. The higher the bonding zone between the forged substrate and AM part, the higher the longitudinal and transverse main tensile stress zone, and the normal tensile stress was concentrated at the wall corners. The residual stress of the components using reciprocating scanning was much lower than that using single-direction scanning.