5052 aluminum alloy is a typical alloy of 5xxx series alloys. Its Mg content is between 2.2% and 2.8%. It belongs to low Mg, heat-treated non-reinforceable aluminum alloys. It has medium strength, good corrosion resistance, weldability, and easy machining. Features.
The alloy has good plasticity in the annealed state and high work hardening rate, so it has low plasticity in the hard state. After the hot-rolled sheet, when the alloy has a cold working rate of 50%, the recrystallization temperature is about 288 ° C. Mg is the only strengthening element in the alloy, which has a certain solid solution strengthening effect, and improves the work hardening rate of the alloy, and the alloy can obtain more obvious strain strengthening.
5052 alloy is often used as a decorative panel material because of its excellent formability, corrosion resistance, weldability, and fatigue strength. With the development of machinery, automobile and other related industries, the demand for 5052 aluminum alloy sheet is increasing, and its research is mainly focused on the alloy welding machining. Now let’s take a look at the aluminum-magnesium alloy welding features of 5052 aluminum alloy:
1.Strong reducing ability
The affinity of aluminum and oxygen is very strong. Aluminum easily combines with oxides in the air to form a dense and strong A1203 film with a thickness of about 0.1 μm. The melting point of A1203 is as high as 2050 ° C, which is much higher than the melting point of aluminum and aluminum alloys (500 -600 ° C). During the welding machining, the oxide film will hinder the good bonding between metals and easily cause slag inclusion. The aluminum oxide film also absorbs moisture, which can cause welds to form pores during welding.
2.High thermal conductivity and specific heat capacity
The thermal conductivity and specific heat capacity of aluminum and aluminum alloys are more than twice that of carbon steels and low alloy steels. During the welding machining, a large amount of heat is quickly transmitted to the interior of the base metal. Therefore, when welding aluminum and aluminum alloys, the heat is removed. Consumption outside the molten metal, more unnecessary consumption in other parts of the metal.
3.Large thermal cracking tendency
The linear expansion coefficient of aluminum is about 22.9x 10-6 / ℃, and the iron is 11.7 x10-6 / ℃. The linear expansion coefficient of aluminum and aluminum alloy is about twice that of carbon steel and low alloy steel. The volume shrinkage of aluminum during solidification is large, up to 6.5%, while that of iron is 3.5%, so aluminum and aluminum alloys are prone to shrinkage, shrinkage, thermal cracking and high internal stress when welding.
4.High stomatal sensitivity.
Liquid molten pools of aluminum and aluminum alloys can easily absorb gases such as hydrogen. A large amount of gas dissolved at high temperature is too late to precipitate during the cooling and solidification machining after welding, and pores are formed in the weld. The moisture in the arc column atmosphere, the moisture absorbed by the welding material and the oxide film on the surface of the base material are all important sources of hydrogen in the weld.
5.No color change during solid liquefaction
When the molten pool metal of aluminum and aluminum alloy is changed from solid to liquid, there is no obvious color change, which brings inconvenience to the welding operation.
Aluminum is a face-centered cubic lattice, there is no allotrope, there is no phase change during heating and cooling, and the grains of the weld are easy to coarsen, and the grains cannot be refined by phase change.
Research shows that 5052 aluminum alloy has good friction stir welding performance, dynamic recrystallization occurs in the weld zone, the weld grains are refined, and the weld can achieve 0 ° C to 180 ° C. Arbitrary bending, optimized machining parameters can make the strength of the welded joint reach or higher than the base metal.