Investigating the Effect of Laser Additive Manufacturing on Microstructure Evolution of Inoculated Zr47.5Cu45.5Al5Co2 Bulk Metallic Glass Matrix Composites

Bulk metallic glass matrix composites are advocated to be material of future owing to their superior
strength, hardness and elastic strain limit. However, they possess poor toughness which makes them
unusable in any structural engineering application. Inoculation has been used as an effective means
to overcome this problem. Zr47.5Cu45.5Al5Co2 bulk metallic glass matrix composites (BMGMC)
inoculated with ZrC have shown considerable refinement in microstructure owing to heterogeneous
nucleation. Efforts have also been made to exploit modern laser-based metal additive manufacturing
to fabricate BMGMC parts in one step. However, the effect of laser treatment on inoculated material is
unknown. In this study, an effort has been made to apply laser based additive manufacturing on
untreated and inoculated BMGMC samples. It is observed that laser treatment not only refined the
microstructure but resulted in change of size, morphology and dispersion of CuZr B2 phase in base
metal, heat affected zone and fusion zone. Morphology of CuZr B2 changed from spheroids to
spherulite under the effect of intense heat observed only when laser power was 500 W and there was
no inoculation. Inoculation was found to resist change of morphology of phases in melted and rapidly
solidified material as no evidence of spherulites was observed in samples treated with ZrC. This effect
is documented with back scattered electron imaging. This provides a basis for further research to
quantify this phenomenon and full-scale part development.