Aluminum Alloy Die Casting Elements - Si, Cu, Mg, Zn, Fe, Mn, Ni, Ti
In the die-casting aluminum alloy materials, silicon (Si), copper (Cu), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni), titanium (Ti), strontium, zirconium, chromium and other elements have an effect on the die-casting
The quality of die castings is related to the selected raw materials. The prerequisite for high-quality die castings is to select high-quality raw materials.
1. Silicon (Si) - die cast aluminum alloy element
Silicon is the main element of most die-casting aluminum alloys. It can improve the casting performance of the alloy. Generally, the content is 9.6% - 12%. When the silicon content exceeds 12%, silicon and aluminum form hypereutectic. When there are many impurities such as copper and iron, hard spots of free silicon appear, making it difficult to cut. High silicon aluminum alloy has a serious corrosion effect on the casting crucible. Silicon and aluminum can form solid solutions. At 577 ℃, the solubility of silicon in aluminum is 1.65%. At room temperature, it is 0.2%. When the silicon content reaches 11.7%, silicon and aluminum form eutectic. The high temperature fluidity, wear resistance, hot cracking tendency and shrinkage of the alloy are improved. The binary aluminum base alloy has high corrosion resistance. When the silicon content in the alloy exceeds the eutectic composition and there are many impurities such as copper and iron, the hard spots of free silicon appear, which makes the machining difficult. The high silicon aluminum alloy corrodes the casting crucible
The effect is serious.
2. Copper (Cu) -- die cast aluminum alloy element
Copper and aluminum constitute a solid solution. When the temperature is 548 ℃, the solubility of copper in aluminum should be 5.65%, and it should drop to about 0.1% at room temperature. The copper content in the alloy is usually 1.5%~3.5%. Increasing the copper content can improve the fluidity, tensile strength and hardness of the alloy, but reduce the corrosion resistance and plasticity, and increase the hot cracking tendency.
3. Magnesium (Mg) -- die cast aluminum alloy element
Adding a small amount of magnesium (about 0.2~0.3%) to the high silicon aluminum alloy can improve the strength and yield limit, and improve the machinability of the alloy. Aluminum alloys containing 8% magnesium have excellent corrosion resistance. When the magnesium content is too high, the casting performance becomes poor, the strength and plasticity at high temperatures are low, and the shrinkage is large when cooling, so hot cracking and porosity are easy to occur.
4. Zinc -- die cast aluminum alloy element
Zinc in aluminum alloy can improve fluidity, casting performance and tensile strength, but hot cracking tendency increases and corrosion resistance decreases, generally less than 1.2%. As for ZL401 aluminum alloy with high zinc content, it has better casting properties, mechanical properties and cutting processing.
5. Iron (Fe) -- die cast aluminum alloy element
All aluminum alloys contain harmful impurities. When the iron content in aluminum alloy is too high, iron exists in the alloy as sheet or needle like structures of FeAl3, Fe2Al7 and Al Si Fe, reducing the mechanical properties. This structure will also reduce the fluidity of the alloy and increase the hot cracking resistance. However, due to the strong adhesion of aluminum alloy to the mold, it is particularly strong when the iron content is below 0.6%. When the iron content exceeds 0.6%, the die sticking will be greatly reduced. Therefore, it is beneficial for die casting to control the iron content within 0.6~1%, but the maximum iron content cannot exceed 1.5%.
6. Manganese (Mn) -- die cast aluminum alloy element
Manganese in aluminum alloy can reduce the harmful effect of iron, and can change the lamellar or acicular structure formed by iron into fine crystal structure. Therefore, generally, less than 0.5% manganese is allowed in aluminum alloy. When the manganese content is too high, it will cause segregation.
7. Nickel (Ni) -- die cast aluminum alloy element
Nickel in aluminum alloy can improve the strength and hardness of the alloy and reduce the corrosion resistance. Nickel has the same effect as iron, which can reduce the corrosion of the alloy on the die, neutralize the harmful effect of iron, and improve the welding performance of the alloy. When the nickel content is 1~1.5%, the casting can obtain a smooth and clean surface after polishing. Due to the lack of nickel sources, aluminum alloys containing nickel should be used as little as possible.
8. Titanium (Ti) -- die cast aluminum alloy element
The addition of trace titanium in aluminum alloy can significantly refine the grain structure of aluminum alloy, improve the mechanical properties of the alloy, and reduce the hot cracking tendency of the alloy
9. Strontium -- die casting aluminum alloy element
Strontium is a surface active element. In crystallography, strontium can change the metal
Behavior of the compound phase. Therefore, modification with strontium can improve the plastic workability and final product quality of the alloy. In recent years, the use of sodium has been replaced in Al Si casting alloys due to the long effective time, good effect and reproducibility of strontium modification. 0.015%~0.03% strontium is added to aluminum alloy for extrusion β- AlFeSi phase becomes Chinese character α- AlFeSi phase reduces the homogenization time of the ingot by 60%~70%, and improves the mechanical properties and plastic processability of the material; Improve the surface roughness of products. For high silicon (10%~13%) wrought aluminum alloy, the addition of 0.02%~0.07% strontium can reduce the initial crystal to the minimum, significantly improve the mechanical properties and tensile strength б B Increase from 233MPa to 236MPa
, yield strength б 0.2 from 204MPa to 210MPa, elongation б 5 From 9% to 12%. Adding strontium into hypereutectic Al Si alloys can reduce the size of primary silicon particles, improve the plastic workability, and can be successfully hot rolled and cold rolled.
10. Zirconium -- die casting aluminum alloy element
Zirconium is also a common additive for aluminum alloys. Generally, 0.1%~0.3% is added to aluminum alloy. Zirconium and aluminum form ZrAl3 compound, which can prevent
The crystallization process refines the recrystallized grains. Zirconium can also refine the casting structure, but its effect is smaller than that of titanium. The presence of zirconium will reduce the refinement of titanium and boron
Effect of grains. In the Al Zn Mg Cu alloy system, zirconium has less effect on the quenching sensitivity than chromium and manganese, so zirconium should be used instead
Chromium and manganese refine the recrystallization structure.
11. Chromium -- die cast aluminum alloy element
Chromium is a common additive element in Al Mg Si, Al Mg Zn and Al Mg alloys. At 600 ℃, the solubility of chromium in aluminum is 0.8%, and it is basically insoluble at room temperature. Chromium forms (CrFe) Al7 and（
Intermetallic compounds such as CrMn) Al12 hinder the nucleation and growth process of recrystallization, have a certain strengthening effect on the alloy, and can also improve the toughness of the alloy and reduce the stress corrosion cracking sensitivity. However, the quenching sensitivity of the venue is increased, making the anodic oxide film yellow. The addition of chromium in aluminum alloy generally does not exceed 0.35%, and decreases with the increase of transition elements in the alloy.
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