Effect of Ti substitution on glass-forming ability and mechanical properties of a brittle Cu–Zr–Al bulk metallic glass

Starting from the brittle Cu46Zr46Al8 bulk metallic glass (BMG), the effect of substituting Al by Ti on the glass-forming ability (GFA) and the mechanical properties is systematically investigated. The supercooled liquid region (ΔTx), the reduced glass transition temperature (Trg=Tg/Tliq) and the γ parameter (γ=Tx/(Tg+Tliq)) tend to decrease with increasing Ti content in the present Cu46Zr46Al8−xTix (0≤x≤8) alloys. An increasing distance from the eutectic point might be the origin of the reduced GFA after the Ti addition. At the same time, the Ti additions significantly increase the plasticity of the respective alloys. The Cu46Zr46Ti3.2Al4.8 bulk glassy alloy is found to have the largest plastic strain in compression of around 12% and a fracture strength up to 1950 MPa while the Ti-free Cu46Zr46Al8 BMG exhibits values of 0% and 1754 MPa, respectively. The statistics of the serrated flow behavior, which is closely related with the dynamics of shear bands, are also investigated. The macroscopic and microscopic mechanisms, which contribute to the enhancement of malleability, are analyzed.