Low-Temperature Brazing of Titanium Using Al-Based Filler Alloys

A Muhrat,J Barbosa,H Puga

doi:10.1155/2018/4570120

A Muhrat, J Barbosa + Show 1 more

Open Access

https://doi.org/10.1155/2018/4570120

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Abstract

Brazing of titanium using low melting temperature filler alloys is a preferred choice regarding cost and preserving its mechanical properties. However, brazing titanium at low temperature is still a challenge, especially regarding aluminum-based filler alloys. During the last years, several brazing methods and Al-based fillers were developed to meet industrial requirements; some of them might achieve some of those requirements. The use of ultrasound in brazing has gained increased attention recently, which helps to reduce the time and the necessity for a special brazing environment, subsequently, reducing cost and increasing applicability. Brazing titanium below the α↔β transformation temperature, using commercial and experimental Al-based fillers of different compositions, is presented in this review; including the procedures of traditional and ultrasound-assisted brazing methods. Correspondingly, the effects of brazing conditions and alloying elements on the mechanical properties and the intermetallic compounds formation are examined.

Highlights

Brazing of titanium at a temperature below α↔β transformation temperature has great importance in avoiding undesirable changes in its original microstructures [1, 2]
The aluminum-based filler alloys for brazing titanium and the formation of the intermetallic compounds at the interface of Ti/filler have been analyzed. e proper design of time-temperature cycle and the controlled alloying additions in the aluminum filler are crucial factors for the intermetallic compound formation at the interface. e thickness and type of the intermetallic phases will largely determine the mechanical properties of the brazed joint
Several technological parameters have been examined for ultrasound-assisted brazing of titanium by Al-based filler alloys, including the acoustic power, the ultrasonic vibration (USV) period, the holding time, the filler thickness, and the brazing temperature; the following points should be highlighted: (i) e holding time after USV is necessary for the diffusion process proceeding at the interface between the filler and the titanium parent metal

Summary

Introduction

Brazing of titanium at a temperature below α↔β transformation temperature has great importance in avoiding undesirable changes in its original microstructures [1, 2]. Ti- and Ti–Zr-based alloys were developed later, which showed better metallurgical compatibility with titanium [12] and produced higher joint strength when compared with the other systems of brazing fillers. Considerable efforts have been made to reduce brazing cycle time while still achieving a suitable strength by employing new techniques and developing new compositions of low-melting filler materials. Brazing time could be increased according to the parent/filler materials’ compositions to allow the interface element diffusion to take place for a certain limit which is necessary to achieve the optimal joint strength. E diffusion of some brazing processes, usually in high temperature, may proceed for a relatively long holding time until achieving the microstructure homogenization over all the joint, which is known as diffusion brazing. Using USV in brazing is an attractive assisting tool [37,38,39, 52,53,54,55,56,57,58]; studying the combined effects of USV with the technological parameters of brazing process and developing a joint interface more compatible with the USV have not yet received an adequate attention. e focus in this review will be on the titanium/aluminum interface which includes Albased filler alloys for brazing titanium/titanium and titanium/aluminum parent (base) components, taking into consideration the technological parameters and procedures

Aluminum-Based Filler Alloys

Main Aluminum-Based Filler Systems

Findings

Conclusions and Future Work