Microstructural characterization of Al_2O_3/AISI 8650 steel joint brazed with Ag-Cu-Sn-Zr alloy

摘要

Sinitered Al_2O_3 was brazed to AISI 8650 steel using a 67Ag-26Cu-5Sn-2Zr (wt./100) brazing alloy. The microstructure of the brazement and the interfacial phase between the Al_2O_3 and brazement was investigated. The single ZrO_2 layer with a monoclinic structure was formed by the migration of Zr in the molten brazing alloy to the Al_2O_3 surface, followed by a redox reaction between them. Smally Ag and Cu particles were present in the reaction layer. The remainder of the brazement formed a Cu-Ag eutectic alloy. Sn was homogeneously distributed within the brazement so that Sn-contained compounds were not formed within the brazement. The Al decomposed from Al_2O_3 diffused into the residual brazing alloy and AISI 8650 steel.