The isothermal wetting and spreading behaviors of molten Zr55Cu30Al10Ni5 metallic glass alloy on B4C substrates were studied using a modified sessile drop method at 1133-1253 K in a high vacuum. A distinct reaction layer consisting of ZrB2 and ZrCx was produced at the interface and displayed good wettability with the molten alloy. The entire spreading kinetics could be characterized by four representative stages: (i) an initial rapid spreading presumably driven by adsorption of the active Zr atoms at the solid-liquid interface, (ii) a quasi-linear and (iii) a linear spreading stage controlled by the chemical reaction between Zr and B4C in both cases, and (iv) an approach-to-equilibrium stage with precipitation of crystals in the liquid. An increase in temperature promotes the wetting and reaction. In view of the reasonable wettability and reactivity, there is a potential for preparing Zr-base bulk metallic glass matrix composites reinforced by in situ ZrC-ZrB2 hybrid ceramic particulates using B4C as a reaction agent by way of an infiltration synthesis technique. (C) 2009 Elsevier B.V. All rights reserved.