Microstructural Observation of Brazed Ti-15-3 Alloy Using the Clad Ti–20Zr–20Cu–20Ni Foil

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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.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase Transformation of a Ti-15Mo-5Zr-3Al Brazed Joint Using Clad Ti-15Cu-15Ni Filler

Yue

Chen

Shiue

et al. 2020

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“…The joining of titanium and its alloys is important in the industry, because joining technology is a fundamental process of manufacturing [1,2]. The similar/dissimilar joining of Ti and its alloys has been widely evaluated in the literature for many applications [3][4][5][6][7][8][9]. Simoes proposed a dissimilar joining of titanium alloys as well as many advanced ceramics, and they produced components with extraordinary and unique properties for the automotive and aerospace industries [10].…”

Section: Introductionmentioning

confidence: 99%

Vacuum Brazing Ti–15–3 with a TiNiNb Braze Alloy

Kao

Tsay

Wang

et al. 2019

Among all types of brazing fillers, Ti-based fillers show satisfactory joint strengths in brazing titanium alloys. However, the major concern in using such fillers is the formation of Cu/Ni/Ti intermetallic compound(s) in the joint. In this study, a Ti–15–3 alloy was vacuum brazed with a clad Ti–35Ni–25Nb foil. The brazed zone consisted of a Ti2Ni intermetallic compound in a (β-Ti,Nb)-rich matrix for specimen brazing at 1000 °C/600 s. Raising brazing temperature and time resulted in the Ti2Ni dissolving into the (β-Ti,Nb)-rich matrix. For the specimen brazing at 1100 °C/600s, Ti2Ni could only be observed at the grain boundaries of the (β-Ti,Nb)-rich matrix. After further raising it to 1200 °C/600 s, the Ti2Ni intermetallic compound was all dissolved into the (β-Ti,Nb)-rich phase. The average shear strength was significantly raised from 140 (1000 °C/600 s) to 620 MPa (1100 °C/3600 s). Crack initiation/propagation in the brittle Ti2Ni compound with the cleavage fractograph were changed into the Ti–15–3 base metal with a ductile dimple fractograph. The advantage of using Nb in the TiNiNb filler foil was its ability to stabilize β-Ti, and most of the Ni in the braze alloy was dissolved into the β-Ti matrix. The brazed joint could be free of any intermetallic phases with a proper brazing cycle applied, and the joint was suitable for a few harsh applications, e.g., repeated stresses and impact loadings.

“…Brazing of Ti and its alloys can be an important issue in application of such materials [8]. Most titanium alloys can be successfully brazed by Ti-(Zr)-Cu-Ni braze alloys [8][9][10]. Traditional Ti-based brazing fillers are alloyed with Cu and Ni as the melting point depressants, and they are featured with moderate brazing temperature and excellent bonding strength.…”

Section: Introductionmentioning

confidence: 99%

The Application of 40Ti-35Ni-25Nb Filler Foil in Brazing Commercially Pure Titanium

Wang

Kao

Tsay

et al. 2018

Self Cite

The clad ternary 40Ti-35Ni-25Nb (wt %) foil has been applied in brazing commercially pure titanium (CP-Ti). The wavelength dispersive spectroscope (WDS) was utilized for quantitative chemical analyses of various phases/structures, and electron back scattered diffraction (EBSD) was used for crystallographic analyses in the brazed joint. The microstructure of brazed joint relies on the Nb and Ni distributions across the joint. For the β-Ti alloyed with high Nb and low Ni contents, the brazed zone (BZ), consisting of the stabilized β-Ti at room temperature. In contrast, eutectoid decomposition of the β-Ti into Ti 2 Ni and α-Ti is widely observed in the transition zone (TZ) of the joint. Although average shear strengths of joints brazed at different temperatures are approximately the same level, their standard deviations decreased with increasing the brazing temperature. The presence of inherent brittle Ti 2 Ni intermetallics results in higher standard deviation in shear test. Because the Ni content is lowered in TZ at a higher brazing temperature, the amount of eutectoid is decreased in TZ. The fracture location is changed from TZ into BZ mixed with α and β-Ti.