An experimental technique to study the molten filler metal flow in brazed joints has been developed. Of prime importance in brazing processes, liquid filler metal flow in braze joints can be characterized by fundamental physical and chemical principles in terms of capillary action. This experimental method provides an important tool to analyze the flow properties in-situ. Not only can the data obtained using this technique explain how the molten filler metal flows, they can also provide information on wetting, spreading, and viscosity change with temperature, chemical reactions occurring at the substrate/filler metal interface, fillet formation and the effect of substrate surface conditions.

The experimental setup consists of three main parts: a furnace, a high-speed, high magnification imaging system and a temperature controller. Each test specimen contains two reservoirs joint by a horizontal and parallel gap of height approximately 100 mm, length of 5 mm and a depth of 5 mm. The solid filler metal is placed in the left reservoir of the gap and flows to the right once it reaches its molten state. The acquired data are collected and analyzed for the determination of the dynamic flow properties of the filler metal. The experiments are carried out in a controlled inert gas atmosphere to promote wetting and provide oxidation protection to the substrate. Each specimen is analyzed using metallographic techniques, light microscopy, scanning microscopy and energy dispersive spectroscopy.