Study On Preparation And Characteristic Of Aluminum Base Composite Filler Metal

6063 aluminium alloy has been More and more widely applied in many industries, especially in the aerospace sector. Al-Si filler metal has been more and more widely applied in brazing aluminium alloy for it has satisfactory weldability. Production offen scrop by overheated when it is brazing. Because of the the low solid phase temperature of 6063 aluminum alloy This study aims to develop a kind of low melting-point Al-Si filler metal to solve the problem of 6063 aluminium alloy that it is exist in brazing.A new type of low melting-point aluminium base composite filler metal was prepared by electroplating copper and nickel on Al-12Si alloy foil,like Ni/Cu/Al-Si/Cu/Ni.The brazing mechanism of the filler metal and the characteristic of the welding joint has been studied in this paper by differential scanning calorimetry(DSC),scanning electron microscope, electron probe microanalysis.ect. The results:Melting point,wettability etc.which belong to the new type of aluminium base composite filler metal satisfy requirement of brazing 6063 aluminium alloy, the wettability is very good, too.Tensile strength of the welding joint 6063 aluminium alloy is the same as some other Al-Si filler metal which have a high melting point. So it can be applied in brazing 6063 aluminium alloy instead of Al-Si filler metal.The wetting process of new type of aluminium base composite filler metal is composed of five stages.The first stage is physical wetting, in which a liquid filler metal on a solid surface will spread to some extent on the surface and then comes to rest reaching a first metastable equilibrium comtact angle.The second stage is the formation of liquid phase between Al-Si and copper interface.The third stage is the dissolving of copper layer, nickel layer breakage and elimination. The fourth stage is liquid phase layer extension and uniformity. The amorphous bonding is characterized as the last stage.Nickel element increase the wettability of the filler metal,beside that it keep copper element from diffusing into base metal.Nickel layer keeps 6063 aluminium alloy body material away from filler metal that aviod the occurrence of contact eutectic reaction In the initial stage of filler metal welding.it avoid the longitudinal diffusion from filler metal to aluminium alloy material that in favour of improving the wettability of the filler metal.Nickel layer was broken later in filler metal welding.A mound of nickel was expeled from welding joint with excess filler metal,only a little nickle still remained in welding joint.The nickel layer reduce the dissolving of base metal On the one hand, the nickle element that dissolved in liquid improve the wettability of filler metal.On the other hand,it improve the tensile strength of welding joint.Especially, nickle layer keep copper layer from being oxidized. Because copper is easy to oxidize in the air.