Abstract
Furnace brazing of Ti-15Mo-5Zr-3Al (Ti-15-5-3, β-Ti) alloy using clad Ti-15Cu-15Ni foil as the filler in a high vacuum has been carried out. In the brazed joints, the chemical compositions of distinct phases were quantified by electron probe micro-analyzer (EPMA), and the phase structures were identified by electron backscatter diffraction (EBSD). The as-brazed joint composed of α-Ti, retained β-Ti, Ti2Ni, and Ti2Cu. The embrittlement of the brazed joint was correlated mainly with the formation of intermetallics, especially cellular Ti2Ni dendrites in the brazed zone. It was noticed that the molten filler liquated the β-Ti grain boundaries and assisted the eutectic reaction therein, resulting in forming grain boundary Ti2Ni surrounded by the retained β-Ti. The results indicated that proper brazing conditions were able to eliminate all the harmful phases effectively, and increased the shear strength of the Ti-15Mo-5Zr-3Al brazed joint.
Highlights
Titanium alloys with excellent specific strength and corrosion resistance are attractive as structural materials used in the aerospace industry [1,2,3,4]
The fracture features of the shear-fractured samples were examined with an scanning electron microscope (SEM), and the causes of shear fracture were further related to the inherent microstructures of the brazed joint
The X-ray diffractometer (XRD) pattern revealed that Ti2 Ni mixed with
Summary
Titanium alloys with excellent specific strength and corrosion resistance are attractive as structural materials used in the aerospace industry [1,2,3,4]. Excellent fatigue strength of Ti-15-5-3 alloy solution-treated in the alpha/beta region results from higher crack initiation resistance, due to the microstructure, which is composed of primary α phase and a fine β matrix [9]. Cu-based amorphous filler is used for brazing TiAl alloy for high temperature applications [26]. The use of Ti-based fillers to braze Ti alloys has become an important issue nowadays, because the brazed joint features with better corrosion resistance and mechanical properties [27]. It is reported that the formation of Ti-Cu/Ti-Ni intermetallic compounds deteriorates joint strength [28,29,30]. In an attempt to achieve a high-strength joint, the impact of brazing time periods was investigated under a fixed brazing temperature of 1243 K (970 ◦ C) in this work. The fracture features of the shear-fractured samples were examined with an SEM, and the causes of shear fracture were further related to the inherent microstructures of the brazed joint
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