Aluminum is the most abundant metal and the third most abundant element in the earth's crust, after oxygen and silicon. It makes up about 8% by weight of the earth’s solid surface. Aluminum also chemically reactive to occur naturally as the free metal (Kobayashi et al, 2002). There are many applications of Aluminum in our daily life, such as construction machinery, aircraft construction, ship construction, home furnishing and electronics component. For the vehicle industry, Aluminum has established a worldwide position because of its advantages over the other competitive materials, like light weight, providing exceptional unit strengths (strength/density ratio), high corrosion resistance, low maintenance costs, good temperature resistance (even in arctic environments), ductile, easily joined by all commercial processes such as welding, brazing, or soldering, at the last, aluminum can be easily formed by ...view middle of the document...
There is no stiffness advantage in using aluminum over steel. Basically, strength refers to the maximum load that a material can be subjected to without yielding, whereas stiffness refers to how much a material bends when a load is applied. Stiffness is quantified by a parameter called Modulus of Elasticity. Steel’s modulus is about 3 times stronger than Aluminum but steel’s weight is about 3 times heavier than aluminum.
Aluminum welding with other metals is very difficult because there are problems like different melting points, physical natures and other intermetallic differences. Kee-Hyun et al. (2006) presented that intermetallic diffusion in interface Al and steel is formed. The Intermetallic Compound For motion (IMC) is rapidly developed and grows between the steel and the melt. Only aluminum diffuses into the steel substrate without the dissolution of iron at the interface of the steel-intermetallic compound.
The primary diffusing species of the hot dip aluminizing process in this study is aluminum. Al coating on the steel and the short dipping time prevent the iron from dissolving into the aluminum melt. The IMC is confirmed to be Fe2SiAl8 with a hexagonal unit cell (space group P63/mmc).Temizel et al, (2007) also showed that the intermetallic phases FeAl2 and Fe2Al5 were the most dominant phases that could be observed, that they were formed sequentially, in contrast to intermetallic, which formed synchronously in bulk materials. A good diffusion interface cannot be formed if the heating temperature is too low, since extent of diffusion is not sufficient even though the holding time is longer and the pressure is larger. But, if the heating temperature is too high, the grains will grow up seriously and the diffusion transition zone can become wider, which will adversely affect the performance of the diffusion bonding joint (Yajiang et al, 2005). The test results indicated that the heating temperature should not be lower than 1000°C in order to ensure the interface combination. Therefore, this paper aims to determine the effect of holding time on the diffusion characteristics of the joint with the 6061 aluminum and Carbon steel filler using Cu and Fe.