Microstructural Investigation of AgCuZnSn Brazed Joints in Additively Manufactured 316L Stainless Steel

This study provides novel insights into the influence of additive manufacturing (AM)-induced grain texture on the solidification behavior of AgCuZnSn filler metal during brazing—a phenomenon not previously reported. The AM surface was shown to affect the crystallographic orientation of the filler metal, suggesting that control over AM texture can be used to tailor the properties of brazed joints. Systematic characterization of the joint microstructure was carried out using SEM, EDS, and EBSD techniques.

AM enables the fabrication of complex geometries, but the limited part size often necessitates joining. Brazing is a suitable method for this, though further study is required to understand the interactions between AM surfaces and filler metals. In this work, AM 316L stainless steel tiles were brazed to machined SS316L cylinders using an AgCuZnSn filler metal. Variables included flux type and filler metal quantity.

Microstructural characterization focused on grain size and orientation in the joint region, particularly at the interfaces between the filler and the two different base materials. All samples exhibited porosity at the filler–cylinder interface. Two main phases were identified in the filler: a Cu-rich and an Ag-rich phase, with the Cu-rich phase forming globular structures at the AM tile interface. Notably, grain structures differed between the two interfaces.

The sample brazed with MetaBraze LT 21 showed similar crystallographic orientation in the filler and AM base metal, suggesting a more isotropic response during deformation. These findings indicate that controlling AM-induced texture could serve as a strategy to engineer the microstructure and performance of brazed joints.