Research on Additive Manufacturing at UQ

Ming-Xing Zhang, Han Huang, Michael Bermingham, Matthew Dargusch Source: Andrew Kostryzhev, Queensland Branch of Materials Australia

The University of Queensland (UQ) has historical research strengths in the field of metals, including solidification, grain refinement, alloy development, surface engineering, lead-free soldering, and processing. UQ has been the headquarters of the CAST CRC since 1993, and was a key member in the ARC Centre of Excellence for Design in Light Metals. UQ materials engineering received the ARC ERA rating of five, in 2010, 2012, 2015 and 2018. In recent years, additive manufacturing (AM) has been listed as one of the university’s major research priorities. With funding support from ARC, industry partners and UQ internal grants, the university’s team has made significant contributions to this area of research.

Professor Ming-Xing Zhang’s group focuses on development of new techniques, including AM process control and discovery of new additives to increase the AM processability, as well as the design of new alloys that are especially suitable for AM. One recent invention is a new titanium alloys that can be produced in-situ by mixing additives with the feedstock together with a chemical functionalisation for surface charge modification of the metal powder particles. The laser powder bed fusion (L-PBF) fabricated new alloys exhibiting a yield strength of over 1.0GPa with elongation over 23%, benchmarked against Ti-6Al-4V powder (850 MPa and 10% strain) purchased off-shelf. Figure 1 compares the yield strength and elongation of the new alloys with previously reported titanium alloys fabricated with AM. Another invention is the discovery of nanoparticles that can be integrated into pure copper powder via ultrasonic vibration and mechanical mixing to reduce the surface reflectance and enable facile fabrication of highly dense pure copper parts via AM. This overcame a long-term problem of L-PBF of pure copper. The L-PBF fabricated pure copper parts exhibit the tensile strength of 400 MPa accompanied with the elongation of 24%, but still retain 95% of the thermal and electrical conductivity of the annealed wrought pure copper. Figure 2 shows the comparison of previously published data of copper alloys with the currently L-PBF fabricated pure copper in terms of tensile strength, elongation and electrical conductivity (C). Over the past several years, Professor Han Huang’s group has been developing advanced structural ceramics and ceramic coatings on metal substrate using laser-based additive manufacturing (LAM) techniques. Compared with the conventional fabrication approaches, LAM techniques have apparent advantages in the preparation of near-net-shape complex ceramic components in terms of microstructure refinement, efficiency, cost and forming capability. The group is now capable of synthesising single phase ceramics such as alumina and zirconia, and binary and ternary eutectic oxides such as Al2O3-YAG and Al2O3YAG-ZrO2 that present similar density and mechanical properties to those fabricated using the conventional methods. They have also used LAM to successfully fabricate hard and wear-resistant TiOx ceramic coatings and TiOxNy reinforced α-Ti composite coatings on Ti alloys. Through the ARC Research Centre for Advanced Manufacturing of Medical Devices, Professor Matthew Dargusch and Dr Michael Bermingham’s group is exploring AM to produce metal alloys suited to medical devices. Permanent (non-degradable) alloys including titanium, stainless steel and cobalt-chrome have long been used for implant materials and are commercially produced into a range of medical devices by AM. The team is exploring ways to eliminate manufacturing waste and improve product quality in the production of medical devices, as well as developing new fit for purpose alloys. Another emerging interest for some applications is biodegradable metals. Challenges include understanding how such materials can be reliably processed by AM (for instance, many biodegradable metals, including magnesium and zinc, have high vapour pressures and tend to evaporate during fusion based AM processes such as Selective Laser Melting), as well as understanding the degradation rate and biological response to these materials in the body. Their work also explores the role of design in medical devices produced by AM, with a focus on exploiting the full potential of AM to create unique structures that are suitable for medical device applications.