Bulk metallic glass composites containing B2 phase

•Three “M-glasses” alloys and one B2-containing Mg-based glassy composites have been classified.•Microstructure, GFA and mechanical behaviours have been discussed and compared.•Both as-cast and annealed “M-glasses” BMG composites are categorized and discussed.•The possible future work on “M-glasses” composites has been proposed. The brittleness and work-softening of Bulk Metallic Glasses (BMGs) prevent their wide applications as structural engineering materials. In order to settle this problem, the BMG composites containing B2 phase with lower shear modulus and body-centred cubic structure (BCC) via in-situ or ex-situ modes were developed. Although a lot of attempts have been proposed to enhance the plastic deformation, the work-softening remained unsettled before the concept of transformation-induced plasticity (TRIP) in steels was introduced about ten years ago. The BMG composites incorporating the B2 phase possess the macroscopically plastic deformability and work-hardening induced by the martensitic transformation (MT) from B2 to B19′ or B33 upon uniaxial loading. Since then, many studies focus on formation of the B2 phase in Zr- and Ti-based BMG composites and the effect of B2 phase on tensile plasticity and strain-hardening. Although the enhanced plastic strain and work-hardening under compression have been extensively obtained, the improved tensile ductility and work-hardening of BMG composites have been scarcely achieved. To get a thorough understanding about formation of the B2 phase and its effect on mechanical properties, a comprehensive review is critically important and necessary, which is the aim of the present work.