【Deep Coating Society Popular Science Knowledge】Discuss the advantages and disadvantages of the influence of each element in aluminum alloy on the performance of aluminum alloy?

Abstract: Aluminum alloys exhibit different performance characteristics
due to the addition of different metal elements.
Among the 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), zinc (Zn), etc.
, the following introduces the influence of these metal elements on the properties of
aluminum alloys.

1.
Copper (Cu)

Copper is an important alloying element in aluminum alloy, which has a certain solid solution strengthening effect, and CuAl2 precipitated by aging has a significant aging strengthening effect
.

Advantages: solution strengthening and aging strengthening effect is good, copper content in 4% to 6.
8% when the strengthening effect is the best, so most of the duralumin alloy copper content 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 plasticity, so that the tendency of hot cracking increases
.

2.
Magnesium (Mg)

The strengthening of magnesium to aluminum is significant, and for every 1% increase in magnesium, the tensile strength increases by about 34MPa
.
If less than 1% manganese is added, it may add a reinforcing effect
.
Therefore, manganese addition can reduce the magnesium content, while reducing the tendency to hot cracking, in addition, manganese can also make the Mg5Al8 compound average precipitation, improve corrosion resistance and welding function
.

Advantages: Improve tensile strength and yield limit, improve machinability
of alloys.

Disadvantages: Mg2Si will make castings brittle
.

3.
Silicon (Si)

The maximum solubility of Mg2Si in aluminum is 1.
85%, and decreases with the decrease of temperature, deformed aluminum alloy, silicon alone added to the aluminum plate is limited to welding materials, silicon added to aluminum also has a certain strengthening effect
.

Advantages: Improve the casting properties
of the alloy.
Silicon and aluminum can form a solid solution, which can improve the high-temperature modeling of the alloy, reduce shrinkage, and have no tendency to
hot cracking.
Improve tensile strength, hardness, machinability and strength at high temperatures while reducing
elongation.

Disadvantages: The crystallized silicon (Si) is prone to hard spots of free silicon, which makes the machinability worse, and the high silicon aluminum alloy has a serious
erosion effect on the casting crucible.

4.
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 as a sheet or needle-like structure of FeAl3, Fe2Al7 and Al-Si-Fe, forming metal compounds and forming hard spots
.
This structure also reduces mechanical properties, increases thermal cracking, and makes castings brittle
.
And when the amount of iron (Fe) exceeds 1.
2%, it reduces the fluidity of the alloy, damages the quality of the casting, and shortens the life
of metal components in the die-casting equipment.

5.
Manganese (Mn)

The maximum solubility of manganese in a solid solution is 1.
82%.

The strength of the alloy increases with increasing solubility, and the elongation reaches a maximum at a manganese
content of 0.
8%.
Al-Mn alloy long-term and short-term aging hardening alloy, that is, it cannot be strengthened by
heat treatment.

Advantages: Alloy strength increases
with increasing solubility.
At a manganese content of 0.
8%, the elongation reaches a maximum
.
Manganese (Mn) can stop the recrystallization process of aluminum alloys, increase the recrystallization temperature, and significantly refine the recrystallization grains
.
The refinement of recrystallized grains mainly hinders the growth of recrystallized grains through the dispersion particles of MnAl6
compounds.
Another function of MnAl6 is to dissolve impurity iron (Fe) to form (Fe, Mn)Al6, so that the sheet or needle-like structure formed by iron in the aluminum alloy becomes a fine crystal structure and reduces the harmful effects
of iron.

Disadvantages: When the manganese content is too high, it will cause segregation
.

6.
Nickel (Ni)

Advantages: There is a tendency to increase tensile strength and hardness, which has a great
influence on corrosion resistance.

Disadvantages: Reduced corrosion resistance and thermal conductivity
.

7.
Zinc (Zn)

Advantages: Zinc and magnesium are added to aluminum at the same time to form a strengthening phase Mg/Zn2, which will have a significant strengthening effect
on the alloy.

Disadvantages: There is a tendency to
stress corrosion cracking.

Source: Eighth Element Material Edition Statement: This number is neutral to reprint, share, state and opinion, the purpose is only for industry communication, and the copyright belongs to the original author
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