Researchers from Monash University, based in Melbourne, Australia, have published a study which demonstrates the use of Additive Manufacturing to develop an ultra-strong titanium alloy via the manipulation of its microstructure. The research, published in Nature Materials, was done on commercially available material.
The researchers used Laser Beam Powder Bed Fusion (PBF-LB) to manufacture from ß-titanium alloy powders, exploiting the inherent thermal cycling and rapid cooling Additive Manufacturing to achieve a nanoprecipitation microstructure that the researchers believe is a first of its kind.
The additively manufactured parts were subjected to heat treatments at two different temperatures (480 and 520ºC); the tensile stress-strain curves of as-built and post-processed parts were measured. From the curves, the thermally treated samples showed what the researchers called an unexpectedly high level of strength, with a 50–70% relative improvement over the as-built sample. In particular, the UTS after the 480°C post-heat treatment reached the level of 1,611 MPa whilst maintaining a good uniform elongation of 5.4%.
“Titanium alloys require complex casting and thermomechanical processing to achieve the high strengths required for some critical applications,” stated Professor Aijun Huang. “We have discovered that Additive Manufacturing can exploit its unique manufacturing process to create ultra-strong and thermally stable parts in commercial titanium alloys, which may be directly implemented in service.”
He continued, “After a simple post-heat treatment on a commercial titanium alloy, adequate elongation and tensile strengths over 1,600 MPa are achieved – the highest specific strength among all 3D printed metal to date. This work paves the way to fabricate structural materials with unique microstructures and excellent properties for broad applications.”
The process is said to offer a new approach to precipitation strengthening commercial titanium alloys which will enable them to be used in load-bearing applications, making them well suited to aerospace, space, defence, energy and biomedical industries.
‘Ultrastrong nanotwinned titanium alloys through additive manufacturing’ was led by Professor Huang and Dr Yuman Zhu alongside Kun Zhang, Zhichao Meng, Kai Zhang, Peter Hodgson, Nick Birbilis, Matthew Weyland, Hamish L Fraser, Samuel Chao Voon Lim, Huizhi Peng, Rui Yang and Hao Wang. The paper is available here, in full.