Towards the additive manufacturing of Zr-based metallic glasses using liquid phase sintering: Reactivity and phase transformation kinetics at the crystalline/amorphous interface

Bulk metallic glasses (BMG) present great potential for high-tech applications considering the excellent mechanical and corrosion properties. The on-going development of powder additive manufacturing techniques offers the opportunity to produce rather large parts composed of BMG. Relative to the sinter based additive manufacturing techniques, the sintering of a Zr-based BMG (AMZ4, Zr59,3Cu28,8Al10,4Nb1,5) using Zn-based additives was identified as promising: Zn alloys have indeed a melting point (Tm,Zn = 419, 5 & LCIRC;C) lower than the crystallization temperature of the BMG (Tx & SIME; 470 & LCIRC;C). Here, the study focuses on the understanding of the reactivity between AMZ4 and Zn as a function of temperature and time. A powder blend and a model interface AMZ4/Zn were studied combining post-mortem characterizations (SEM, EDX, XRD, micro-hardness...) with in situ characterization (DSC). Experimental construction of time-temperature-transformation diagram shows that there is a temperature/time window where sintering is permitted without crystallization. Beyond, an intermetallic phase is formed at the interface between the BMG and Zn, this phase was identified in terms of shape, composition and crystallography. A growth mechanism was proposed combining thermodynamic and kinetic aspects.