Hot workability and microstructure evolution of pre-forms for forgings produced by additive manufacturing

Abstract

Abstract Additive Manufacturing (AM) processes allow for near-net shape production of components without dies or substantial machining. Especially for energy-intensive materials, AM processes offer a reduction in lead-time, and in some cases also of yield loss and cost. However, the properties and microstructure of the parts fabricated by AM will not reach the level of forged material without using expensive downstream processes such as hot-isostatic pressing. Using the specific advantages of both processes, AM 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. The present study focusses on the investigation of the microstructure evolution during heat treatment and hot working of Ti–6Al–4V specimens which were produced by means of selective laser melting (SLM). The results show that the microstructure and strain hardening of specimens produced by SLM and conventional wrought material differ for forming temperatures below 1000°C. SLM specimens show a higher resistance to plastic deformation than conventional stock material. Above 1000°C, the flow stress behaviour and resulting microstructure are very similar. The results show that hot working of 3D-printed pre-forms is viable and should preferentially be performed in the β-phase.