AAE Research Seminar Series - Effects of in-situ rolling on the microstructure and mechanical properties of additively-manufactured aerospace metallic materials

Abstract

Monash Centre for Additive Manufacturing (MCAM) continuous to put major emphasis on fundamental research and transforming fundamentally innovative ideas into practical applications. On this basis, MCAM developed a revolutionary hybrid additive manufacturing technology based on our deep understanding of the additive manufacturing process and the real demand for aerospace components. The technology concept was to combine conventional rolling deformation (micro-rolling) with direct energy deposition (DED) to overcome the longstanding columnar grain and stochastic defects issues since they lead to strongly anisotropic mechanical properties and inferior dynamic properties that impede the qualification and applications of the final products. The designed technology has been applied to produce titanium alloy (Ti-6Al-4V) and nickel-based superalloy (Inconel 718) for initial proof of concept. Through this hybrid technique, excellent isotropic tensile properties were achieved for thin-wall components of Ti-6Al-4V. The strength and uniform elongation along two mutually perpendicular directions exhibited good consistency with negligible property scatter. Our studies revealed that the isotropic tensile properties were associated with the formation of nearly equiaxed prior-β grains with internal α grains exhibiting weaker textures. The application of the hybrid technique to Inconel 718 resulted in a novel hierarchical refined grain structure in the microstructure due to the unique dynamic and meta-dynamic recrystallisation induced by the micro-rolling during DED. Through this, an average grain size of ~8 µm and a much weaker texture were achieved for the micro-rolled samples. Tensile tests showed that a significant increase of over 50% in the yield strength was achieved for the micro-rolled samples at both room temperature and 650°C, while maintaining a good uniform elongation above 10%.

Speaker

Professor Aijun Huang is a full professor in the Department of Materials Science and Engineering, Monash University. Prof Huang is also the Director of Monash Centre for Additive Manufacturing, which hosts the largest number of state-of-art metal 3D printing facilities in Australia. His research covers the entire spectrum of metal additive manufacturing (AM). Prior to his appointment at Monash University, Prof Huang was an industry technical expert for a number of multinational corporations. Prof Huang held the position of the Executive Vice President of The High Performance Materials Business Unit of the Baosteel Group; a Fortune Global 500 company. From 2006 to 2012, Prof Huang was the Titanium Specialist of Rolls Royce plc, Derby United Kingdom. Unique combination of his broad industrial experience and in-depth academic research has bring over $15 million AUDs fund from industrial since he joined Monash in 2017 which lead to two prestigious research awards from Vice-Chancellor and Dean of Engineering in Monash University. He has established a world class cross-functional research group currently consisting of 10 postdoctoral research fellows, 5 professional staff, and 16 PhD students which is one of most active research groups in metal additive manufacturing field.