Tailoring modulus and hardness of in-situ formed β-Ti in bulk metallic glass composites by precipitation of isothermal ω-Ti

Publication date: 5 November 2017
Source:Materials & Design, Volume 133
Author(s): L. Zhang, S. Chen, H.M. Fu, H. Li, Z.W. Zhu, H.W. Zhang, Z.K. Li, A.M. Wang, H.F. Zhang
It is challenging to tailor the mechanical properties of in-situ formed β phases in Ti/Zr-based bulk metallic glass composites (β-type BMGCs) without changing the morphologies of the β phases. Recently, BMGCs containing metastable β-Ti/Zr phases (metastable β-type BMGCs) exhibit an exothermic reaction below the glass transition temperature (sub-Tg) of the glassy matrices during heating, however, the corresponding structural origin remains unclear. In this work, the precipitation of ω phase inside β phase was revealed to account for the sub-Tg exothermic event of the metastable Ti45.7Zr33Cu5.8Co3Be12.5 BMGC. The sub-Tg annealing of metastable β-type BMGCs causes the precipitation of nanometer-sized isothermal ω phase, which leads to a large increase in the modulus and hardness of the crystalline phase. This finding provides a novel route to tailor the modulus and hardness of the crystalline phases in BMGCs without changing their morphologies, including volume fractions, sizes, and distributions. On this basis, the influence of the modulus and hardness of the crystalline phase on mechanical properties of BMGCs was exclusively investigated. Our experimental results together with finite-element simulations proved that lower modulus and hardness of the crystalline phase benefit a larger plasticity of BMGCs.

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