1. Copper

 

Copper is an important alloy element, which has a certain solution strengthening effect. In addition, CuAl2 precipitated by aging has a significant aging strengthening effect. The copper content in aluminum plate is usually 2.5% - 5%, and the strengthening effect is best when the copper content is 4% - 6.8%, so the copper content of most duralumin alloys is in this range.

 

2. Silicon

 

The maximum solubility of Mg2Si in aluminum in the aluminum rich sector of the equilibrium phase diagram of Al Mg2Si alloy system is 1.85%, and it slows down with the decrease of temperature. In deformed aluminum alloys, silicon added to aluminum plates alone is limited to welding materials, and silicon added to aluminum also has a certain strengthening effect.

 

3. Magnesium

 

The strengthening of magnesium on aluminum is significant. The tensile strength increases by about 34MPa for every 1% increase of magnesium. If less than 1% manganese is added, the strengthening effect may be added. Therefore, adding manganese can reduce magnesium content and hot cracking tendency. In addition, manganese can make Mg5Al8 compound precipitate averagely, improving corrosion resistance and welding function.

 

4. Manganese

 

The maximum solubility of manganese in solid solution is 1.82%. The strength of the alloy increases with the increase of solubility. When the manganese content is 0.8%, the elongation reaches the maximum. Al Mn alloy is a long and short age hardening alloy, that is, it cannot be strengthened by heat treatment.

 

5. Zinc

 

The solubility of zinc in aluminum is 31.6% at 275 in the aluminum rich section of the equilibrium phase diagram of Al Zn alloy system, while it drops to 5.6% at 125. When zinc is added to aluminum alone, the improvement of aluminum alloy strength is very limited under the premise of deformation. At the same time, there is a tendency of stress corrosion cracking, which limits its application.

 

6. Iron and silicon

 

Iron in Al Cu Mg Ni Fe forged aluminum alloys, silicon in Al Mg Si forged aluminum and in Al Si electrodes and Al Si forged alloys are all added as alloy elements. In other aluminum alloys, silicon and iron are common impurities, which have a significant impact on the alloy function. They mainly exist as FeCl3 and free silicon. When silicon is greater than iron β- FeSiAl3 (or Fe2Si2Al9) phase is formed when iron is larger than silicon α- Fe2SiAl8 (or Fe3Si2Al12). When the proportion of iron and silicon is not appropriate, it will cause cracks in the casting, and when the iron content in the cast aluminum is too high, it will make the casting brittle.

 

7. Titanium and boron

 

Titanium is a commonly used addition element in aluminum alloy, which is added in the form of Al Ti or Al-Ti-B master alloy. Titanium and aluminum form TiAl2 phase, which becomes the non spontaneous core during crystallization and plays a role in refining the forging structure and weld structure. When Al Ti alloys undergo ladle reaction, the critical content of titanium is about 0.15%, and the deceleration is reduced to 0.01% in the presence of boron.

 

8. Chromium and strontium

 

Chromium forms intermetallic compounds such as (CrFe) Al7 and (CrMn) Al12 in aluminum plate, which hinder the nucleation and growth process of recrystallization, strengthen the alloy to a certain extent, improve the toughness of the alloy and reduce the stress corrosion cracking sensitivity. However, the quenching sensitivity of the venue is increased to make the anodic oxide film yellow. The amount of chromium added to the aluminum alloy generally does not exceed 0.35% and decreases with the increase of transition elements in the alloy. The addition of 0.015%~0.03% strontium to the aluminum alloy for extrusion makes the ingot β- AlFeSi phase becomes Chinese character α- AlFeSi phase reduces the average time of ingot by 60%~70%, and improves the mechanical function and plastic workability of materials; Improve the roughness of product surface. For high silicon (10%~13%) wrought aluminum alloy, the addition of 0.02%~0.07% strontium can reduce the initial crystal to the minimum, and the mechanical performance is also improved significantly, and the tensile strength б B The yield strength increases from 233MPa to 236MPa б 0.2 from 204MPa to 210MPa, elongation б 5 From 9% to 12%. Adding strontium into hypereutectic Al Si alloy can reduce the size of primary silicon particles, improve the plastic processing function, and can be successfully hot rolled and cold rolled.