Al-Ag-Ge合金熔凝过程中液相流动机制与旋涡组织形成的相关规律研究

Fluid flow and solidification mechanisms of Al₇₀Ag₂₀Ge₁₀ alloy were systematically investigated using electromagnetic levitation, induction, arc, and resistance melting techniques coupled with finite element simulation method. A unique type of vortex-shaped microstructure was formed in these four experiments. This was different from the result under slow solidification conditions. The formation of the vortex-shaped structure was affected by fluid flow and cooling rate of alloy melt. The Lorentz force caused turbulent flow in alloy melt, while the turbulent flow during arc melting was driven by arc force under electromagnetic levitation or induction melting conditions. The surface tension and buoyancy force caused laminar flow in alloy melt during the resistance melting process. Due to rapid flow, the Ag₂Al phase nucleated ahead of the Al phase, primarily under near-equilibrium conditions. The metastable Ag₂Al dendrites grew as vortex-shaped morphology and preserved the melt flow pattern during solidification. The increased cooling rate caused a rapid growth of metastable Ag₂Al dendrites with increased vortex density. The curvature radius of metastable Ag₂Al dendrites decreased with enhanced melt flow; meanwhile, the more drastic nucleation and growing competition among phases occurred. Finally, irregular Al, Ag₂Al, and Ge ternary eutectics fully formed inside the vortex-shaped structure.