Aluminum alloys show different performance characteristics due to the addition of different metal elements, just like a dish, with different condiments to form different flavors. Among the various metal elements, the elements that have a greater influence on the performance of aluminum alloys are copper (Cu), magnesium (Mg), silicon (Si), iron (Fe), manganese (Mn), nickel (Ni), and zinc (Zn ), Chromium (Cr), calcium (Ca), etc. Today we will talk about the impact of these metal elements on the performance of aluminum alloys.
Copper (Cu)
Advantages: solid solution strengthening and aging strengthening effect, the strengthening effect is best when the copper content is 4% to 6.8%, so the copper content of most hard aluminum alloys is in this range. Increase the copper content, improve the fluidity, tensile strength and hardness of the alloy, so that the mechanical properties can be improved and the machinability becomes better.
Disadvantages: reduce corrosion resistance and shaping, increase the tendency of hot cracking.
Magnesium (Mg)
Advantages: Improve tensile strength and yield limit, improve the cutting machinability of the alloy.
Disadvantages: Mg2Si will make the casting brittle.
Silicon (Si)
Advantages: improve the casting performance of the alloy, silicon and aluminum can form a solid solution, improve the high-temperature moldability of the alloy, reduce shrinkage, and have no tendency to hot cracking. Binary aluminum-based alloys have high corrosion resistance. Improve tensile strength, hardness, machinability and strength at high temperature, and reduce elongation. Silicon is also the main component to improve the flow performance, from eutectic to hypereutectic can get the best fluidity.
Disadvantages: The crystallized silicon (Si) is prone to hard spots of free silicon, which makes the machinability worse. The high-silicon aluminum alloy has a serious corrosion effect on the casting crucible.
Iron (Fe)
Advantages: The adhesion of aluminum alloy to the mold is very strong, especially when the iron content is below 0.6%, that is, it is not easy to demold. When the iron content exceeds 0.6%, the sticking phenomenon is greatly reduced.
Disadvantages: When the iron content in the aluminum alloy is too high, the iron exists in the alloy in the form of flakes or needles of FeAl3, Fe2Al7 and Al-Si-Fe, forming metal compounds and forming hard spots. This structure will also reduce the mechanical properties, increase the thermal cracking, and make the casting brittle. And when the content of iron (Fe) exceeds 1.2%, the fluidity of the alloy is reduced, the quality of the casting is impaired, and the life of the metal components in the die casting equipment is shortened.
Manganese (Mn)
Advantages: The strength of the alloy increases with the increase of solubility. When the manganese content is 0.8%, the elongation reaches the maximum value. Manganese (Mn) can prevent the recrystallization process of the aluminum alloy, increase the recrystallization temperature, and can significantly refine the recrystallized grains. The refinement of recrystallized grains is mainly due to the dispersion of MnAl6 compound particles to hinder the growth of recrystallized grains. Another function of MnAl6 is to dissolve the impurity iron (Fe) and form (Fe, Mn) Al6, so that the sheet-like or needle-like structure formed by iron in the aluminum alloy becomes a fine crystal structure, reducing the harmful effects of iron.
Disadvantages: When the manganese content is too high, it will cause segregation.
Nickel (Ni)
Advantages: There is a tendency to increase the tensile strength and hardness, which greatly affects the corrosion resistance.
Disadvantages: reduce corrosion resistance and thermal conductivity.
Zinc (Zn)
Advantages: Zinc and magnesium are added to aluminum at the same time to form the strengthening phase Mg / Zn2, which has obvious strengthening effect on the alloy.
Disadvantages: There is a tendency to stress corrosion cracking.
Chromium (Cr)
Advantages: Chromium (Cr) forms (CrFe) Al7 and (CrMn) Al12 and other intermetallic compounds in aluminum, hinders the nucleation and growth process of recrystallization, has a certain strengthening effect on the alloy, and can improve the alloy toughness and reduce Stress corrosion cracking sensitivity.
Disadvantages: increased quenching sensitivity.
Calcium (Ca)
Advantages: Calcium has very low solid solubility in aluminum alloys and forms CaAl4 compounds with aluminum. Calcium is also a superplastic element of aluminum alloys. Aluminum alloys with about 5% calcium and 5% manganese have superplasticity. Calcium and silicon form CaSi2, which is insoluble in aluminum. Due to the reduced solid solution of silicon, the conductivity of industrial pure aluminum can be slightly improved. Calcium can improve the cutting performance of aluminum alloys. Trace amounts of calcium are beneficial for removing hydrogen from the aluminum liquid.
Disadvantages: CaSi2 can not strengthen the heat treatment of aluminum alloy.

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