The role of the hottest elements in aluminum alloy

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Role of various elements in aluminum alloy

1 Influence of alloy elements

copper element cu

when the aluminum rich part of aluminum copper alloy 548, the maximum solubility of copper in aluminum is 5.65%, and when the temperature drops to 302, the solubility of copper is 0.45%. Copper is an important alloy element, which has certain solid solution strengthening effect. In addition, CuAl2 precipitated by aging has obvious aging strengthening effect. The copper content in aluminum alloy is usually 2.5%~ 5%, and the strengthening effect is the best when the copper content is 4%~6.8%, so the copper content of most duralumin alloys is in this range

aluminum copper alloys can contain less silicon, magnesium, manganese, chromium, zinc, iron and other elements

silicon element si

al Si alloy system the maximum solubility of silicon in solid solution is 1.65% at the eutectic temperature of 577. Although the solubility decreases with decreasing temperature, this kind of alloy can not be strengthened by heat treatment. Al Si alloy has excellent castability and corrosion resistance

if magnesium and silicon are added to aluminum at the same time to form an Al Mg Si alloy, the strengthening phase is MgSi. The mass ratio of magnesium to silicon is 1.73:1. When designing the composition of Al Mg Si alloy, the content of magnesium and silicon shall be configured on the matrix according to this ratio. In order to improve the strength of some Al Mg Si alloys, an appropriate amount of copper and chromium are added to offset the adverse effect of copper on corrosion resistance

al-mg2si alloy system alloy equilibrium phase diagram the maximum solubility of aluminum rich Mg2Si in aluminum is 1.85%, and the deceleration decreases with the decrease of temperature

In the deformed aluminum alloy, the addition of silicon to aluminum alone is limited to welding materials, and silicon also has a certain strengthening effect

magnesium element mg

al Mg alloy system equilibrium phase diagram aluminum rich part although the solubility curve shows that the solubility of magnesium in aluminum decreases greatly with the decrease of temperature, in most industrial deformed aluminum alloys, the content of magnesium is less than 6%, and the content of silicon is also low. This kind of alloy cannot be strengthened by heat treatment, but it has good weldability, good corrosion resistance and medium strength

the strengthening effect of magnesium on aluminum is obvious. For every 1% increase in magnesium, the tensile strength increases by about 34mpa. If less than 1% manganese is added, the strengthening effect may be supplemented. Therefore, when the a/d converter operates at the "maximum output data rate of 4kHz", adding manganese can reduce the magnesium content and reduce the hot cracking tendency. In addition, manganese can make mg5al8 compound precipitate evenly, and improve the corrosion resistance and welding performance

The maximum solubility of manganese in solid solution is 1.82% at the eutectic temperature of 658 for the horizontal equilibrium phase diagram of Mn

al Mn alloy system. 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 non age hardening alloy, that is, it cannot be strengthened by heat treatment

manganese can prevent the recrystallization of aluminum alloy, improve the experimental waveform crystallization process, increase the recrystallization temperature, and significantly refine the recrystallized grains. The refinement of recrystallized grains is mainly through the dispersion particles of mnal6 compound, which hinders the growth of recrystallized grains. 4. Conference cost: 2000 yuan/person. Another function of mnal6 is to dissolve impurity iron to form (Fe, Mn) al6 and reduce the harmful effect of iron

manganese is an important element in aluminum alloys. It can be added alone to form al Mn binary alloys, and more often with other alloy elements. Therefore, most aluminum alloys contain manganese

zinc element zn

al Zn alloy system equilibrium phase diagram the solubility of zinc in aluminum is 31.6% at 275, while it decreases to 5.6% at 125

when zinc is added to aluminum alone, the strength improvement of aluminum alloy under deformation conditions is very limited. At the same time, there is a tendency of stress corrosion cracking, which limits its application

when zinc and magnesium are added to aluminum at the same time, the strengthening phase mg/zn2 is formed, which has an obvious strengthening effect on the alloy. When mg/zn2 content is increased from 0.5% to 12%, the tensile strength and yield strength can be significantly increased. The content of magnesium exceeds that of the superhard aluminum alloy required to form mg/zn2 phase. When the ratio of zinc to magnesium is controlled at about 2.7, the stress corrosion cracking resistance is the largest

if copper is added to Al Zn mg to form Al Zn mg Cu alloys, the base strengthening effect is the largest among all aluminum alloys, and it is also an important aluminum alloy material in aerospace, aviation industry and power industry

2. Influence of trace elements

iron and silicon Fe si

iron is added as alloy elements in Al Cu Mg Ni Fe forged aluminum alloy, silicon in Al Mg Si forged aluminum and in Al Si welding rod and Al Si cast alloy. In other aluminum alloys, silicon and iron are common impurity elements, which have a significant impact on alloy properties. They mainly exist as FeCl3 and free silicon. When silicon is larger than iron, it forms 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, the casting will produce cracks. When the iron content in cast aluminum is too high, the casting will produce brittleness

titanium and boron ti-b

titanium is a common additive element in aluminum alloys, 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 casting structure and weld structure. The critical content of titanium is about 0.15% when Al Ti alloys produce ladle reaction. If boron exists, the deceleration will be reduced to 0.01%

chromium cr

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 almost insoluble at room temperature

chromium 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, improves the toughness of the alloy and reduces the susceptibility to stress corrosion cracking. However, the quenching sensitivity was increased at the venue, making the anodic oxide film yellow

the addition amount of chromium in aluminum alloy is generally not more than 0.35%, and decreases with the increase of transition elements in the alloy

strontium sr

strontium is a surface active element. In crystallography, strontium can change the behavior of intermetallic compounds. Therefore, modification with strontium can improve the plasticity of the alloy and the quality of the final product. In recent years, strontium has replaced sodium in Al Si casting alloys because of its long effective modification time, good effect and reproducibility. Add 0.015%~0.03% strontium into aluminum alloy for extrusion to β- Alfesi phase turns into Chinese character shape α- Alfesi phase reduces the homogenization time of ingot by 60%~70%, and improves the mechanical properties and plastic workability of the material; Improve product surface roughness. Adding 0.02%~0.07% strontium to high silicon (10%~13%) wrought aluminum alloy can reduce the primary crystal to the minimum, significantly improve the mechanical properties and tensile strength б B from 233mpa to 236mpa, yield strength б 0.2 from 204mpa to 210mpa, elongation б 5 from 9% to 12%. Adding strontium to hypereutectic Al Si alloy can reduce the size of primary silicon particles, improve the plastic workability and smooth hot rolling and cold rolling

zirconium element zr

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 hinder the recrystallization process and refine the recrystallized grains. Zirconium can also refine the casting structure, but its effect is less than that of titanium. In the presence of zirconium, the grain refinement effect of titanium and boron will be reduced. In Al Zn mg Cu alloys, zirconium has less effect on quenching sensitivity than chromium and manganese, so zirconium should be used instead of chromium and manganese to refine the recrystallization structure

impurity element re

rare earth elements are added to the aluminum alloy to increase the component undercooling, refine the grain, reduce the secondary crystal spacing, reduce the gas and inclusions in the alloy, and make the inclusion phase tend to spheroidize. It can also reduce the surface tension of the melt, increase the fluidity, and is conducive to casting into ingots. Because there are more and more simple bridges to be built, it has a significant impact on the process performance. The addition amount of rare earth is about 0.1%at%. The addition of mixed rare earth (LA CE PR nd, etc.) makes al-0.65%mg-0.61%si alloy age G? The critical temperature for the formation of P-zone decreases. Aluminum alloys containing magnesium can stimulate the modification of rare earth elements

3. Influence of impurity elements

vanadium forms val11 refractory compound in aluminum alloy, which plays a role in refining grain during casting, but has a smaller role than titanium and zirconium. Vanadium can also refine the recrystallization structure and increase the recrystallization temperature

the solid solubility of calcium in aluminum alloys is very low, forming 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 CASI, which is insoluble in aluminum. Since the solid solution of silicon is reduced, the conductivity of industrial pure aluminum can be slightly improved. Calcium can improve the machinability of aluminum alloy. Casi2 can not strengthen aluminum alloy by heat treatment. Trace calcium is helpful to remove hydrogen from molten aluminum

lead, tin and bismuth are low melting point metals. Their solid solubility in aluminum is small, which slightly reduces the strength of the alloy, but can improve the cutting performance. Bismuth expands during solidification, which is beneficial to feeding. Adding bismuth to high magnesium alloys can prevent sodium embrittlement

antimony is mainly used as a modifier in cast aluminum alloys, but rarely used in wrought aluminum alloys. It can only replace bismuth in Al Mg wrought aluminum alloy to prevent sodium embrittlement. Antimony is added to some Al Zn mg Cu alloys to improve the hot pressing and cold pressing process properties

beryllium in wrought aluminum alloy can improve the structure of oxide film and reduce burning loss and inclusions during melting and casting. Beryllium is a toxic element, which can cause allergic poisoning. Therefore, beryllium cannot be contained in aluminum alloys in contact with food and beverages. Beryllium content in welding materials is usually controlled at 8 μ Below g/ml. The content of beryllium should also be controlled for aluminum alloys used as welding substrates

sodium is almost insoluble in aluminum. The maximum solid solubility is less than 0.0025%. The melting point of sodium is low (97.8 ℃). When sodium is present in the alloy, it is adsorbed on the dendrite surface or grain boundary during solidification. During hot processing, the sodium on the grain boundary forms a liquid adsorption layer. When brittle cracking occurs, naalsi compound is formed. There is no free sodium and "sodium embrittlement" does not occur. When magnesium content exceeds 2%, magnesium captures silicon and precipitates free sodium, resulting in "sodium embrittlement". Therefore, sodium salt flux is not allowed for high magnesium aluminum alloy. The method to prevent "sodium brittleness" is chlorination method, so that sodium forms NaCl and is discharged into the slag, and bismuth is added to make it form na2bi and enter the metal matrix; Adding antimony to form na3sb or adding rare earth can also play the same role. (end)

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