Development of a processing route for Ti-6Al-4V forgings based on preforms made by selective laser melting

Abstract

Additive manufacturing (AM) provides an alternative for small scale production of various metal components. However, due to the inherent porosity, the performance of AM-parts will not reach the level of forged material unless further processes such as hot-isostatic pressing are used. Alternatively, additive manufacturing could be combined with forging operations to novel process chains, offering the possibility to reduce the number of forging steps and to create near net-shape forgings with desired local properties. In the present study, the design of a novel processing route using additively manufactured preforms for hot working is considered. The microstructure evolution of AM pre-forms is investigated during hot working and heat treatment and compared to conventional wrought material with a lamellar microstructure typically used for forgings. The results show that pre-forms made from Ti-6Al-4 V by SLM show a good hot workability due to the martensitic microstructure. Void closure is observed to occur in hot compression under compressive stresses. As a consequence, the proposed processing route appears to allow for similar final microstructures and hence properties as conventional forging process chains, but may reduce the number of forging steps to a single one and hence reduce the number of dies as well as the die loads.