Title：Additive manufacturing of ultrafine-grained high-strength titanium alloys

Speaker: QIU Dong

Time：Dec 18,2019  14:00-16:00

Host:WANG Huiyuan

Location:Room 209 , College of Materials Science and Engineering

Abstract：

Additively manufactured (AM) titanium alloys have been used in numerous applications, in particular in the biomedical and aerospace industries due to the greater material efficiency and enhanced design flexibility. However, for many conventional titanium alloys, the AM process usually results in a microstructure comprised of coarse columnar grains, which often leads to undesirable anisotropic mechanical properties. In contrast to other common engineering alloys, such as aluminium, there is no commercial grain refiner, containing potent inoculants that can survive in liquid titanium, able to control microstructure effectively. To address this challenge, we have developed a novel technique for AM by using Ti-Cu alloys with a high constitutional supercooling capacity that overrides the negative effect of a high thermal gradient in the melt pool during AM. Through this approach, it is shown that an as-printed Ti-Cu alloy specimen is comprised of fully equiaxed, fine grained microstructure without any special process control or additional subsequent treatment. The new AM Ti-Cu alloys also display promising mechanical properties, compared to conventional alloys under similar processing conditions, due to the formation of an ultrafine eutectoid microstructure by taking full advantage of the high cooling rates and multiple thermal cycles in the AM process. We anticipate that this approach will be equally applicable to other eutectoid forming alloy systems.