Aluminium-Silicon-Magnesium Filler Metal for Aluminium Vacuum Brazing Wettability and Characteristics of Brazing Microstructure

Abstract

Mg 2 Si composite was added to Al-Si ller metal for aluminium alloy vacuum brazing via in situ synthesis. Spreading area method was used to measure the wettability of the brazing alloy on the parent metal in vacuum. The ller metal wetting area increased with increasing Mg 2 Si content. The compound within the interface was examined with an electron probe and the following results were obtained: Mg 2 Si content of the brazing interface was lower than that of ller metal, Mg 2 Si was distributed into both sides of the interface and arranged in block, grain and short rod-like shapes. Si crystal had a primarily needle-like structural arrangement. The elemental distribution on both sides of the interface was analysed using thread scanning method. A solid solution of Mg was formed in the interior parts of the grain in the parent metal. The solid solution content decreased as the distance from the interface increased.

UQ eSpace

“…Wetting at the liquid solid interface is further enhanced by mass transfer through diffusion (Yang, Zhang, Wang, & Huang, 2016). The braze filler material diffuses with the base metal to ensure joint properties approach the properties of the base metal and hence achieving uniform part composition (H.M. Cobb, 2012).…”

“…The braze filler material diffuses with the base metal to ensure joint properties approach the properties of the base metal and hence achieving uniform part composition (H.M. Cobb, 2012). As stated by Fick's second law, diffusion is dependent on the concentration gradient of the flow path of a particle (Yang, Zhang, Wang, & Huang, 2016). In brazing, large differences in element/compound concentrations between the base and the filler alloy results in diffusion from the filler to the base material (Yang, Zhang, Wang, & Huang, 2016).…”

“…This secondary soaking step is implemented in the brazing cycle to ensure uniform brazing temperatures are reached inside the furnace (Kowalewski & Szczurek). The braze soak time however must be kept to a minimum, to avoid excessive vaporisation of the filler alloy (Moller & Grann) and corrosion of the base metal (Yang, Zhang, Wang, & Huang, 2016).…”

“…Recent theories suggest that the addition of certain elements to the filler alloy can improve the Brazeability and the mechanical properties of an aluminium brazed joint (Sharma, Shin, & Jung, 2015). A supporting investigation observed the effects of adding Magnesium silicide (Mg2Si) to a 4xxx series Al-Si brazing alloy (Yang, Zhang, Wang, & Huang, 2016). It was found that increasing the Mg2Si content in the filler alloy, resulted in an increase in the filler metal wetting area (Yang, Zhang, Wang, & Huang, 2016).…”

“…A supporting investigation observed the effects of adding Magnesium silicide (Mg2Si) to a 4xxx series Al-Si brazing alloy (Yang, Zhang, Wang, & Huang, 2016). It was found that increasing the Mg2Si content in the filler alloy, resulted in an increase in the filler metal wetting area (Yang, Zhang, Wang, & Huang, 2016).…”