Viscosity, structure and fragility of Ag-Si melts

Viscosities and liquid structures of Ag100-xSix (x=5, 7, 9, 11, at.%) melts were studied by an oscillating viscometer and an X-ray diffractometer. Temperature dependence of viscosity and the correlation length D all can be fitted well by Arrhenius equation. The activation energy for viscous flow Ea,V and the activation energy for structural evolution Ea,D all increase with increasing Si content. Above the liquidus temperature, the coordination number Ns, the correlation radius rc, the atom numbers in the cluster Nc and the correlation length D all increase with decreasing temperature. Among them, rc and Nc show a significant increase near the liquidus temperature. In the liquid-solid interval, the structural parameters show different behaviors with temperature due to the influence of the liquid-solid equilibrium reaction of the precipitation phase. Based on the investigated viscosity and structure, the fragility parameter of superheated melts M and the structural fragility parameter Fs were calculated. Both M and Fs increase with increasing silicon content. This work provides us a further understanding of the liquid-solid transition from the perspective of liquid structure and dynamics.