Cold crystallization behaviour of a commercial Zr44-Ti11-Cu10-Ni10-Be25 metal glassy Alloy AVERSA Raffaella 1,a , TAMBURRINO Francesco 1,b , PARCESEPE Daniela 1,c and APICELLA Antonio 3,d 1 Advanced Material Lab, Department of Architecture and Industrial Design Second University of Naples, 81031 Aversa (CE) ITALY a raffaella.aversa@unina2.it , b francesco.tamburrino@unina2.it, c daniela.parcesepe@unina2.it, d antonio.apicella@unina2.it Keywords: Liquid metals, processing, cold crystallization, DSC Abstract. Isothermal crystallizations in the supercooled liquid metal metastable state at progressively increasing temperatures above the Glass Transition of the Zr44-Ti11-Cu10-Ni10-Be25 metal glass Alloy (cold crystallization attained by heating the samples from the glassy state) have been investigated in this study. Complex crystallization behaviours showing multiple exothermic peaks and selective crystallization of the alloy higher mobility atoms induced by the isothermal annealing, has been observed to lead to experimentally observed increase of the temperature needed to induce the glassy metal relaxation (glass transition). DSC dynamic investigation indicated that only two atomic species present in the metastable liquid are involved in recrystallization process below 450-470°C. Isothermal annealing in the range of temperatures between 400° and 450°C has been chosen for further investigation on thermal events kinetics occurring in the super-cooled liquid. The activation energies associated to the two crystallization processes are, respectively, -181 kJ/mol and -262 kJ/mol Introduction Although research on metallic glasses have been started since early ‘60s [1] leading to the development of several metallic alloys with pronounced glass-forming ability [3-5], processing of these glass metal forming systems shows not simply to solve challenges especially when complex shapes components are processed. Critical casting thicknesses, the maximum thickness that a Bulk Metallic Glass (BMG) forming liquid sample can be cast amorphous, may represent a criticality in a melt cast process. Component direct casting and solidification from the melt needs, in fact, understanding of the crystallization process of the bulk metal glass forming alloy and cooling rates sufficiently fast to avoid during the filling the mould cavity undesired localized crystallizations while preserving a homogeneous vitrification in all parts of the processed component. Even for fabrication of simple geometries through direct casting of BMGs, cautious choice of processing parameters, namely, slow mould filling and bulk temperature control are needed, which is challenging when fast cooling is required. [6,7]. Thermoplastic polymers technologies are progressively being transferred to BMGs processing. The metal glass can be reheated from the glassy state and shaped in the temperature region where the glass relaxes into a metastable supercooled liquid before its eventual crystallization starts [4]. Plasticization of a BMG forming alloy in its Super Cooled Liquid Region can be used for thermoplastic forming. Due to recent advances in BMG alloy and thermoplastic forming process development, some BMG formers can be considered high-strength alloys that can be processed like plastics. The main criticities, however, still arise from occurrence of undesired crystallization and phase separation that may strongly reduce the metal glass alloy mechanical properties (tenacity and strength) [6].