Copper and copper alloys are widely used in the aqueous environmental application because of their properties in such environment, copper and copper alloys are antimicrobial, they are also have strong mechanical and corrosion resistant properties in aqueous environmental. The combination of these properties has made them a desirable material for many kind of aqueous environmental applications such as condenser tubing, water intake screens, offshore structure, drinking water piping and cooling systems of electrical generators. One of the most widely used methods of joining copper and its alloys is brazing.
Many different types of pure metals and alloys of brazing filler materials are developed, they are available in a variety of forms, they are foil, paste, sheet, powder, wire, rod etc. This to reduce the difficulties of the process putting them between the base metals as various metals have different physical shapes and properties. The process requires a lot of attention and care in order to minimize the gaps in the metals that are being joined which could lead to failure of the brazed joints. The basic qualities of these filler metals that are prerequisites for the successful base metals bonding are : strength, workability in high temperatures and corrosion resistance. There is a large number of metals and alloys and all of them have different compositions, which makes it a critical point to carefully compare and choose the filler metals. The properties and characteristics of the filler metals should essentially match the properties of the base metals to be joined..
However, filler metals are generally divided based on their working temperatures. Aluminum and aluminum alloys commonly brazed with filler metals that the working temperatures are in the range of 450 to 600oC. Filler metals with working temperatures in the range of 600 to 850oC usually intended for pure copper and some engineering materials, while in the range of 850 to 900oC working temperatures, filler metals designed for brazing in association with methyl borate gas flux. Furthermore, above 900oC filler metals are meant to braze in reducing atmospheres, under inert gas or in vacuum.
The families of phosphorus-containing brazing alloys are the most favored when joining copper and copper-base alloys. These alloys have a unique property, the ability to join copper, without using a flux. [1,2,3]. Silver addition to a copper-phosphorus brazing alloy is well known not only improving its flow characteristic, but also increasing its ductility. Indeed, when silver combined with the alloy, the flow characteristic is more better in regard to the effect of silver that lowering the brazing temperature. Furthermore, better properties in ductility possibly gained at the equal flow characteristic of the silver-free brazing alloy [4,5]. The copper-silver-phosphorus brazing alloys have much attention as consequences of some good properties when used for joining. However, the failures arise...