Development In Aluminum Alloys For Automotive Industry – Heat Treatment Of Aluminum Alloys | Diecasting-mould

Aluminum Alloys For Automotive Application

Aluminum alloy is a kind of alloy made by non-metal fusion. While maintaining the basic performance of pure aluminum, aluminum alloy material has good comprehensive performance. Aluminum alloy material makes smelting process more simple and casting performance better. Aluminum alloy also reduces the production cost of auto parts and is widely welcomed in the automotive industry. At present, many automotive aluminum alloy die casting processes in China adopt metal mold pressure casting process and gravity casting process. The aluminum alloy material used in the cylinder of German automobile engine reduces the quality of the automobile by one third. The new type of Japanese automobile is using the new type aluminum cylinder transmitter. The high-pressure die casting process is adopted to make the cylinder wall thin and the cylinder strength higher. Aluminum alloy materials have been used in cylinder block, cam, cylinder head and so on.

High Strength Material Of Aluminum Alloy

7000 series aluminum alloy is now the highest room temperature strength aluminum alloy, 7000 series aluminum alloy because of strong impact resistance, high strength, suitable for the manufacture of automobile safety insurance and anti-collision system. The early 7075 series aluminum alloy, compared with 7000 series aluminum alloy, added Zn, Mg and other elements, developed 7050, 7079 alloy. The content of Fe and Si elements is reduced, the purity of the alloy is improved, and the aluminum alloy 7A55 with better properties is produced. The alloy has high plasticity and is one of the highest strength aluminum alloys disclosed at present.

Aluminum alloy 2000 series is the earliest heat treatment aluminum alloy. The room temperature strength of the alloy is lower than that of 7000 series aluminum alloy, but its crack resistance is better. Through constant reduction of alloy proportion and impurities, 2419, 2618 and other alloys are introduced, and their application in aviation industry is expanding continuously.

Aluminum alloy 6000 series has very good forging performance, no oxide skin on the surface during hot forging, good surface quality after forging, small machining allowance and strong corrosion resistance. It is welcomed by automobile manufacturers in the automotive industry. 6000 series aluminum alloy is suitable for the manufacture of key auto parts such as rocker arm, control arm, steering knuckle, engine bracket, power transmission frame, etc.

Heat Treatment Of Aluminum Alloys

1. Annealing

The core technology of annealing process is to eliminate the inhomogeneous phenomenon in the structure and composition of ingot. This annealing process is called homogenization annealing. After annealing process, the state of easy cold working can be obtained. At this time, it is full annealing. When the internal stress of the processed casting is eliminated, this annealing process is called stress annealing.

2. Homogenizing

Homogenizing is used to redistribute the precipitating elements more evenly throughout an aluminum part. This is typically necessary when working with cast aluminum alloy parts. When the part begins to cool, the outside edge that is in direct contact with the mold will cool first. This results in a skin of aluminum grains, or crystals. As the part continues to cool inward, the result is fairly pure aluminum near the skin and some regions near the center. The alloying elements precipitate out, resulting in the aluminum grains being locked into place. The cast part ends up with some regions being soft and others being strong. This segregation between regions can be reduced and the resulting part rendered more workable for forming by going through the homogenizing process.

An aluminum part is homogenized by raising its temperature to just under its melting point, which is usually between 900°F to 1000°F. After the entire part has reached this homogenizing temperature, it is allowed to slowly cool. The result is a cast part with a uniform internal structure.

3. Solution Heat Treatment

Solution heat treatment refers to that the solute elements of aluminum alloy melt into the lattice of solvent and form aluminum alloy solution heat treatment after cooling. After solution heat treatment process, the material can also obtain the characteristics of decrease in plasticity and increase in strength.

4. Aging

After aluminum has been solution heat treated, the elements that dissolved will begin to precipitate out over time. This causes the grains to lock into position, which in turn increases the natural strength of the aluminum and is called aging.

The natural aging, or age hardening, process takes place at room temperature over a time period of four to five days, with 90% of the hardening occurring within the first day. Because of this effect, aluminum parts often need to be shaped rather quickly after going through a solution heat treatment process.

5. The Final Heat Treatment

After a series of processes – solution, pre aging, cold deformation, final aging called aluminum alloy final heat treatment. The results show that the properties of the material after the final heat treatment are better than that of the solid solution and aging treatment.

Aluminum alloy materials and heat treatment technology play an important role in improving the development of automotive industry. Automotive industry is the pillar industry of many countries. In recent years, it has been developed continuously and rapidly in China, which has brought great economic and social benefits to the country. Aluminum alloy material is undoubtedly the first choice for the modernization of automobile industry, and aluminum heat treatment technology will be paid more attention.