Aluminum alloy is the most widely used in industry of non-ferrous metal structural materials, in aviation, aerospace, automotive, machinery manufacturing, shipping and have been extensively applied in chemical industry. As the science and technology in recent years, as well as the rapid development of industrial economy, the demand for aluminum alloy welding structure is increasing, also make the weldability of aluminum alloy and research. Aluminum alloy is widely used to promote the development of aluminum alloy welding technology, at the same time, the development of welding technology and expand the application field of aluminum alloy, thus the welding technology of aluminum alloy is becoming one of the hot spot of research.

The density of pure aluminum (rho = 2.7 g/cm3), is about 1/3 of the iron, low melting point (660 ℃), aluminum is face-centered cubic structure, therefore, has the very high plasticity (delta: 32 ~ 40%, and bits of: 70 ~ 90%), easy to machining, can be made into various molding, plate. Corrosion resistant performance is good; But the strength of pure aluminium is very low, annealing state sigma b value is about 8 KGF/was, therefore, not as a structural material. Through the long-term production practice and scientific experiment, people gradually to add alloy elements and using the method of heat treatment to strengthen aluminum, it's got a series of aluminum alloy. Add some elements to form the alloy while maintaining the advantages of pure aluminum light can also has high strength, sigma b value can reach 24 ~ 60 KGF/was respectively. So that its "strength" (the ratio of intensity and the proportion of sigma b/rho) is better than a lot of alloy steel, become the ideal structural material, widely used in machinery manufacturing, transportation, machinery and aviation industry, the aircraft fuselage, skin, such as compressor with aluminum alloy manufacture, in order to reduce weight. The welding of aluminum alloy instead of steel material, the structure can reduce more than 50% in weight.

Aluminum alloy density is low, but the intensity is high, close to or more than high-quality steel, plastic, can be processed into various profiles, with excellent electrical conductivity, thermal conductivity and corrosion resistance, widely used on industry, usage is second only to the steel.

Aluminium alloy is divided into two broad categories: casting aluminum alloy, under the as-cast use; Deformation of aluminum alloy, can withstand the pressure processing,. Can be processed into various forms and specifications of the aluminum alloy material. Mainly used in the manufacture of aviation supplies, building doors and Windows, etc.

Aluminum alloy according to processing methods can be divided into deformation aluminium and aluminium alloy foundry. Deformation of aluminium alloy is divided into an enhanced aluminum alloy heat treatment and heat treatment strengthening type aluminum alloy. An enhanced by heat treatment to improve mechanical properties, heat treatment can only be done by cold deformation strengthening, it mainly includes the high purity aluminum, industrial high purity aluminum, industrial pure aluminum and antirust aluminum, etc. Can be enhanced aluminum alloy heat treatment by quenching and aging heat treatment method to increase mechanical properties, it can be divided into hard aluminum, forging, super-hard aluminum and special aluminum alloy, etc.

Some aluminum alloy can be used in a heat treatment to get good mechanical properties, physical properties and corrosion resistance.

Casting aluminum alloy by chemical composition can be divided into aluminum silicon alloy, copper alloy aluminum, aluminum and magnesium alloys, aluminum zinc alloy and aluminum rare earth alloy, the aluminum silicon alloy and a simple aluminum silicon alloy (not strengthening heat treatment, mechanical performance is low, the casting performance is good), special aluminum silicon alloy, heat treatment reinforcement, high mechanical properties, good casting properties),