​ ​Seminar on Microstructural design of Ti-based bulk metallic glass composites containing in-situ formed β-Ti

Associate Professor Long Zhang

To overcome the catastrophic failure of bulk metallic glasses (BMGs) under unconstrained load, Zr/Ti-based bulk metallic glass composites containing in-situ formed b-Zr/Ti dendrites (b-type BMGCs) were developed two decades ago. In this presentation, a “two-phase quasi-equilibrium” solidification process of b-type BMGCs will be introduced, and b-type BMGCs can be further classified into two kinds: “quasi-equilibrium” BMGCs and “non-equilibrium” BMGCs. Based on this solidification process, the microstructure of the “quasi-equilibrium” BMGCs, including volume fraction, dendrite size, and phase stability of b phases, can be largely altered and controlled. An “iteration method” which can be used to develop b-type BMGCs from Zr/Ti-based BMGs will be also presented. In BMGCs containing metastable b-Ti, it is found that the metastable b-Ti crystals are prone to partially transform to ω phase rather than α phase. If the metastable b-Ti transforms to martensitic phases during deformation, the BMGCs can exhibit large plasticity concomitant high strain-hardening capacity. Additionally, the effect of ω-Ti precipitates on the mechanical properties of b-type BMGCs will be revealed.

Dr. Long Zhang obtained his Bachelor Degree in Materials Science from Beijing Institute of Technology in Jul. 2010 and received the National Scholarship Award from the Ministry of Education of China and the Award of Outstanding Graduate in Beijing. He enrolled for the Ph.D program at the Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS) Sept. 2012. From Oct. 2014 to Mar. 2016 he visited the Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden), Germany. On completing his Ph.D in Materials Science from University of Chinese Academy of Sciences in Jun. 2016 he was awarded the Young Scientist Award from Shenyang National Laboratory for Materials Sciences. From Jul. 2016 to Sept. 2018, he was an assistant professor, and since Oct. 2018, he is an associate professor at IMR, CAS. His has a vast experience in developing and designing of Ti-based bulk metallic glass composites for structural applications.