Spatial and temporal evolution of temperature, hardness, and residual stress in linear friction welding of wrought and 3D-printed near-net blanks

• Established a linear relation between the workpiece burn-off rate and specific power input, eliminating the dependence on experimental data for modelling predictions. • Residual stress evolution during linear friction welding between the printed-to-printed and printed-to-conventional is modelled and validated for the first time in the literature. • Modelled the evolution of temperature, residual stress, and hardness over 150 process combinations, and validated the computed results with 31 measured values. • The higher frictional pressure and the lower rubbing velocity parameter combination yielded joints with excellent structure and properties, with lower residual stresses. • Developed the processing maps for peak temperature, residual stress, and hardness using a 432 data set, which can be used to avoid the undesirable structure and properties. Determining appropriate combinations of process parameters in linear friction welding of Ti6Al4V to obtain defect-free joints while maintaining peak residual stresses within permissible limits remains challenging. Current literature offers limited insights into the underlying process–property relationships, particularly in the welding of both conventional and hybrid near-net couples. The existing process modelling approaches, including fully and loosely coupled thermal-displacement models, could resolve the issue. However, such models are constrained by extensive computational requirements and dependence on experimental inputs, respectively. Therefore, a loosely coupled and experimentally independent thermal–displacement model was developed to compute the temporal and spatial evolution of temperature, hardness, and residual stresses. The dynamic recrystallization and phase transformation kinetics mechanisms are incorporated in the model for accurate prediction of hardness and residual stresses. The analysis was conducted across ∼144 process parameter combinations, and the results were validated using ∼30 measured independent data points. Comprehensive process maps for interfacial peak temperature, hardness, and residual stresses are generated using a 432-size dataset. Overall, the results show that a combination of higher frictional pressure and lower rubbing velocity yields joints with excellent structure, properties and lower residual stresses. The rubbing velocity is a product of the workpiece’s oscillation frequency and amplitude.