Department of Materials

Events

15 September 2021

Effects of in-situ rolling on the microstructure and mechanical properties of additively-manufactured Ti-6Al-4V

Presented By Prof. Aijun Huang - Department of Materials Science and Engineering, Monash University

About this event

One of the main issues of direct energy deposition (DED), which is an additive manufacturing (AM) technique, is the growth of coarse columnar grains caused by heat transfer along the building direction. This results in highly anisotropic mechanical properties that can detrimentally affect the performance and qualification of DED-built components. To address this, a novel rolling device was built and integrated into a DED system so that mechanical rolling can be conducted in-situ as a component is being built. In this study, the integrated system was used to fabricate Ti-6Al-4V and its effects on microstructure and mechanical properties were investigated. Due to in-situ rolling, the prior-β grains that formed were equiaxed and also significantly refined. While the resulting α laths were also less textured, in-situ rolling was found to have a negligible effect on the α lath thickness. The yield and tensile strengths of the rolled alloy were not only found to be isotropic, but also improved as compared to the unrolled equivalent. In terms of ductility, in-situ rolling had a minimal effect on vertically-built samples but total elongation was significantly improved for horizontally-built samples. Lastly, a face-centred cubic (FCC, a = 0.43 nm) phase was observed between the α and β phases in all samples but was found to be coarser in the rolled samples. While the presence of an FCC phase has been reported several times in Ti alloys, the question of whether such a phase is an allotrope of Ti or simply a hydride remains highly controversial.

Prof Huang is the Head of Monash Centre for Additive Manufacturing, which hosts the state-of-art metal 3D printing facilities. His research covers the entire spectrum of metal additive manufacturing (AM): AM specific alloy design; metal powder manufacturing technology; component design for AM; AM process optimisation; post-AM process development including inspection, qualification, and certification of final AM parts.