Microstructural characterization of interfacial reaction products between alumina and braze alloy
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The Al2O3/STS304, Al2O3/Cu and Al2O3/Al2O3 joints were brazed in vacuum with three types of Cu-Ag-Ti brazing filler metals at 1193 K for 1.2 ks. The effects of adherend metals on the microstructure and microchemistry of reaction products formed at the Al2O3/filler metal interface have been investigated. The reaction products of A2O3/STS304 joints showed a layered structure consisting of TiO (monoclinic, a0=0.585 nm, b0=0.934 nm, c0=0.414 nm), Cu2Ti4O (cubic, a0=1.149 nm) and Fe2Ti4O (cubic, a0=1.1297 nm). The TiO compound is a nonstoichiometric titanium monoxide with composition range of TiO0.9 to TiO1.1. Cu2Ti4O and Fe2Ti4O compounds can be considered as (Cu, Fe)2Ti4O because both of them have nearly the same crystal structure and lattice constants. The reaction products of Al2O3/Cu and Al2O3/Al2O3 joints also showed a layered structure consisting of TiO and Cu2Ti4O. The TiO compound was formed by redox reaction between Al2O3 and segregated titanium, whereas Cu2Ti4O and Fe2Ti4O compounds formed by solid-state reaction between TiO and copper from the brazing alloy and iron from the adherend metals, respectively.
KeywordsMicrostructure Titanium Al2O3 Lattice Constant Layered Structure
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