Abstract
The microstructure and mechanical properties of commercial pure titanium (CPTi) and Ti-6Al-4V alloy joints brazed with newly developed Ti-base amorphous filler metals have been investigated by microscopy, electron probe microanalysis, tensile test, fatigue test and salt immersion test.
The developed amorphous filler metals were three kinds of Ti-37.5Zr-15Cu-10Ni, Ti-35Zr-15Cu-15Ni and Ti-25Zr-50Cu. Their melting points were approximately 100°C lower than those of the conventional Ti-base brazing filler metals. With these filler metals, CPTi and Ti-6Al-4V alloy could be brazed at temperatures below α-β transformation (880°C) and β transus temperature (995°C), respectively.
In brazing at temperature below α-β transformation or β transus temperature of base metal used, the original fine structure of the base metal was nearly preserved and a brazed zone was recognized to exist obviously. However, at temperature above these temperatures, the grains of the base metal were coarsened and in the brazed zone the fine acicular phases were observed.
The tensile properties of the joints brazed at temperatures below these transformation temperatures, was compared with that of the base metal and then in brazing for a suitable brazing time, the joint was fractured in the base metal.
From fatigue test results of the Ti-6Al-4V alloy brazed joint, in the joint brazed at temperature below β transus, the fatigue life indicated a fairly good value but all joints failed in the brazed zone. When brazed at 1000°C, joints showed low fatigue life considerably.
The corrosion behavior of the brazed joints was quite equivalent to that of the base metal.
