Interfacial reaction and microstructural evolution of Ag-Cu braze on BaCo0.7Fe0.2Nb0.1O3-δ at high temperature in air. Issue 1 (January 2017) - Zhang, Yuwen
Abstract: Based reactive air brazing technique, interfacial reaction and microstructure formation of Ag-6.6 mol% Cu wetting on BaCo0.7 Fe0.2 Nb0.1 O3-δ (BCFNO) membrane in air were investigated. The interfacial microstructural analysis revealed that at high temperature Ag-Cu alloy transformed into Ag-Cu-O braze in air and the liquid braze penetrated into BCFNO matrix along the grain boundaries. Cu-O in the liquid braze reacted with BCFNO to form CoCuO2 and Ba2 Cu3 O5+x confirmed by XRD. Ridge formed quickly at the triple line as a result of the migration of the interfacial reaction products and in response to the vertical component of force from surface tension. The rapid interfacial reaction and ridging at the spreading front actually stalled the spreading of the liquid braze, rather than a continuous layer of smoother, barrier-free reaction phase forming and driving accompanied spreading. Low macroscopic contact angles between the braze and BCFNO substrate were observed due to the evolution of the ridge composed of the interfacial reaction products near the tripe line.