When there is liquid in the Pipette tip, do not place the pipette horizontally or upside down, so as to prevent the liquid from flowing back and corroding the piston spring.In the process of biological experiments, especially in the field of Cell Culture, the pipette is an indispensable laboratory instrument, and the pipette holder is also used very frequently on the laboratory ultra-clean bench or in the biological safety cabinet. The ease of use of the pipette and the pipette holder also affects the ease of experimental operation.
pipette drying rack,pipette stand for lab,pipette stand for sale,pipette holder for use,rack for pipette Yong Yue Medical Technology(Kunshan) Co.,Ltd , https://www.yypcrtube.com
Copper element
The aluminum-copper alloy-rich aluminum partial equilibrium phase diagram is shown in the figure. At 548, the greater solubility of copper in aluminum was 5.65%, and when the temperature dropped to 302, the solubility of copper was 0.45%. Copper is an important alloying element and has a certain solid-solution strengthening effect. In addition, CuAl2 precipitated during ageing has a significant aging strengthening effect. The content of copper in the aluminum alloy is usually 2.5% to 5%, and the copper content is 4% to 6.8%. The strengthening effect is good, so the copper content of most hard aluminum alloys is in this range.
Aluminum-copper alloys may contain less silicon, magnesium, manganese, chromium, zinc, iron, and other elements.
Silicon element
The Al-Si alloy phase equilibrium phase diagram shows the aluminum rich part as shown in the figure. At a eutectic temperature of 577, the greater solubility of silicon in the solid solution is 1.65%. Although the solubility decreases with decreasing temperature, such alloys are generally not heat-treatable. Al-Si alloys have excellent casting properties and corrosion resistance.
If magnesium and silicon are simultaneously added to aluminum to form an aluminum-magnesium silicon alloy, the strengthening phase is MgSi. The mass ratio of magnesium to silicon is 1.73:1. When designing an Al-Mg-Si-based alloy composition, magnesium and silicon are disposed on the substrate in this ratio. In some Al-Mg-Si alloys, in order to increase the strength, an appropriate amount of copper is added, and an appropriate amount of chromium is added at the same time to offset the adverse effect of copper corrosion resistance.
The Al-Mg2Si alloy-based alloy shows an equilibrium phase diagram of the aluminum-rich part as shown in the figure. The larger solubility of Mg2Si in aluminum is 1.85%, and the deceleration is small as the temperature decreases.
In the deformed aluminum alloy, silicon alone is added to the aluminum and is limited to the welding material. The addition of silicon to the aluminum also has a certain strengthening effect.
Magnesium
The Al-Mg alloy system has an equilibrium phase diagram rich in aluminum as shown in the figure. Although the solubility curve shows that the solubility of magnesium in aluminum is greatly reduced as the temperature decreases, in most industrial deformable aluminum alloys, the magnesium content is less than 6%, and the silicon content is also low, and these alloys cannot Heat-treated, but with good weldability, good resistance to corrosion, and moderate strength.
The enhancement of magnesium by aluminum is obvious. With every 1% increase in magnesium, the tensile strength increases by about 34MPa. If 1% or less of manganese is added, it may supplement the strengthening effect. Therefore, after adding manganese, the content of magnesium can be reduced, and the hot cracking tendency can be reduced. In addition, manganese can evenly precipitate the Mg5Al8 compound and improve the corrosion resistance and welding performance.
Manganese element
The Al-Mn alloy flat balance phase diagram is shown in the figure. At the eutectic temperature of 658, the greater solubility of manganese in the solid solution was 1.82%. The alloy strength increases with the increase of solubility, and when the manganese content is 0.8%, the elongation reaches a large value. Al-Mn alloys are non-aging hardened alloys, ie non-heat treatable.
Manganese can prevent the recrystallization process of the aluminum alloy, increase the recrystallization temperature, and can significantly refine the recrystallized grains. Recrystallization grain refinement is mainly through
The dispersed particles of MnAl6 compound hinder the growth of recrystallized grains. Another role of MnAl6 is to dissolve the impurity iron and form (Fe, Mn)Al6, reducing the harmful effects of iron.
Manganese is an important element of aluminum alloys and can be added separately to form Al-Mn binary alloys, and more is added together with other alloying elements. Therefore, most aluminum alloys contain manganese.
Zinc element
The Al-Zn alloy is a balanced phase diagram with an aluminum-rich part as shown in the figure. At 275 hours, the solubility of zinc in aluminum was 31.6%, while at 125 hours its solubility dropped to 5.6%.
Zinc alone added to aluminum, under the deformation conditions of the aluminum alloy strength is very limited, there is stress corrosion cracking, tend to limit its application.
When zinc and magnesium are added simultaneously in the aluminum, a strengthening phase Mg/Zn2 is formed, which has a significant strengthening effect on the alloy. When the Mg/Zn2 content is increased from 0.5% to 12%, the tensile strength and yield strength can be significantly increased. Magnesium content exceeds that of superhard aluminum alloys required for forming Mg/Zn2 phases. When the ratio of zinc and magnesium is controlled to about 2.7, stress corrosion cracking resistance is large.
If Al-Zn-Mg is added on the basis of copper to form an Al-Zn-Mg-Cu alloy, the base strengthening effect is larger in all aluminum alloys, and it is also an important aluminum alloy material in the aerospace, aviation and power industries. .
2. The influence of trace elements
Iron and silicon
Iron in Al-Cu-Mg-Ni-Fe forged aluminum alloys, silicon is added as an alloying element in Al-Mg-Si series forged aluminum and in Al-Si based electrodes and aluminum-silicon casting alloys. Among the aluminum alloys, silicon and iron are common impurity elements, which have a significant effect on the properties of the alloy. They mainly exist as FeCl3 and free silicon. When silicon is larger than iron, a ?-FeSiAl3 (or Fe2Si2Al9) phase is formed, and when iron is larger than silicon, ?-Fe2SiAl8 (or Fe3Si2Al12) is formed. When the proportion of iron and silicon is not appropriate, cracks may be generated in the casting. When the iron content in the cast aluminum is too high, the casting will be brittle.
Titanium and boron
Titanium is a commonly used additive element in aluminum alloys and is added in the form of Al-Ti or Al-Ti-B master alloys. Titanium forms a TiAl2 phase with aluminum and becomes a non-spontaneous core at the time of crystallization. It functions to refine the cast structure and weld microstructure. When the Al-Ti alloy generates a package reaction, the critical content of titanium is about 0.15%. If there is boron, the deceleration is as small as 0.01%.
chromium
Chromium is a common additive element in Al-Mg-Si, Al-Mg-Zn, and Al-Mg alloys. At 600°C, the solubility of chromium in aluminum is 0.8%, and it is substantially insoluble at room temperature.
Chromium forms intermetallic compounds such as (CrFe)Al7 and (CrMn)Al12 in aluminum, hinders the nucleation and growth of recrystallization, strengthens the alloy, and improves the toughness of the alloy and reduces the stress corrosion cracking susceptibility. . However, the meeting site increases the quench sensitivity, making the anodic oxide film yellow.
The addition of chromium in aluminum alloys generally does not exceed 0.35% and decreases with the increase of transition elements in the alloy.
strontium
Rhodium is a surface active element and crystallographically, it can change the behavior of the intermetallic compound phase. Therefore, deteriorating with niobium can improve the plasticity of the alloy and the quality of the final product. Due to the advantages of long life, good effect and reproducibility, the use of sodium has been replaced in Al-Si cast alloys. The addition of 0.015% to 0.03% niobium to the aluminum alloy for extrusion results in the transformation of the β-AlFeSi phase into a Chinese character α-AlFeSi phase in the aluminum alloy for extrusion, which reduces the ingot homogenization time by 60% to 70% and improves the mechanical properties of the material. Plastic processing; Improve the surface roughness of products. For the high silicon (10%~13%) deformed aluminum alloy added 0.02%~0.07% niobium, the primary crystal can be reduced to a lower limit, the mechanical properties are also significantly improved, the tensile strength бb is increased from 233MPa to 236MPa, yielding Strength б0.2 increased from 204 MPa to 210 MPa, elongation б5 increased from 9% to 12%. Adding niobium to the hypereutectic Al-Si alloy can reduce the size of the primary silicon particles, improve the plastic processing performance, and can be smoothly hot rolled and cold rolled.
Zirconium element
Zirconium is also a common additive for aluminum alloys. Generally, the addition of 0.1% to 0.3% in the aluminum alloy forms zirconium and aluminum to form a ZrAl3 compound, which can hinder the recrystallization process and refine the recrystallized grains. Zirconium can also refine the cast structure, but it is less effective than titanium. The presence of zirconium reduces the effect of titanium and boron grain refinement. In Al-Zn-Mg-Cu alloys, since zirconium has less effect on the quenching sensitivity than chromium and manganese, zirconium is preferred instead of chromium and manganese to refine the recrystallized structure.
Impurity element
The addition of rare earth elements to the aluminum alloy will increase the composition of the aluminum alloy during the casting and will cause excessive cooling, refinement of crystal grains, reduction of secondary crystal spacing, reduction of gas and inclusions in the alloy, and tendency for inclusions to spheroidize. It can also reduce the surface tension of the melt, increase the fluidity, and facilitate the casting into ingots, which has a significant impact on the process performance.
It is good to add about 0.1% at% of various rare earths. The addition of mixed rare earths (such as La-Ce-Pr-Nd mixed) made the critical temperature of the Ag-0.65%Mg-0.61%Si alloy aged in the G?P region decrease. Magnesium-containing aluminum alloys can stimulate the metamorphism of rare earth elements.
Influence of impurity elements
Vanadium forms VAl11 refractory compounds in aluminum alloys, which play a role in grain refinement during the casting process, but is less effective than titanium and zirconium. Vanadium also has the effect of refining the recrystallized structure and increasing the recrystallization temperature.
Calcium has a very low solid solubility in aluminum alloys and forms CaAl4 compounds with aluminum, which is a superplastic element of aluminum alloys. Aluminum alloys with approximately 5% calcium and 5% manganese have superplasticity. Calcium and silicon form CaSi, which is insoluble in aluminum. Since the amount of solid solution of silicon is reduced, the conductivity of industrial pure aluminum can be slightly increased. Calcium can improve the cutting performance of aluminum alloys. CaSi2 cannot strengthen the aluminum alloy by heat treatment. The trace amount of calcium facilitates the removal of hydrogen from the aluminum bath.
Lead, tin, and bismuth are low-melting metals. Their solid solubility in aluminum is small, slightly reducing the strength of the alloy, but it can improve cutting performance. Swelling during solidification favors feeding. The addition of niobium to high magnesium alloys can prevent sodium embrittlement.
Tantalum is mainly used as a modifier in cast aluminum alloys, and deformed aluminum alloys are rarely used. Replacement of niobium in Al-Mg deformed aluminum alloys alone prevents sodium embrittlement. The niobium element is added to certain Al-Zn-Mg-Cu alloys to improve hot-pressing and cold-pressing process performance.
Niobium in the deformed aluminum alloy can improve the structure of the oxide film and reduce the burning loss and inclusion during the casting. Earthworms are toxic elements that can cause allergic poisoning. Therefore, aluminum alloys that come in contact with foods and beverages cannot contain barium. The germanium content in the solder material is usually controlled below 8μg/ml. Aluminum alloy used as a welding base should also control the content of niobium.
Sodium is almost insoluble in aluminum, with a larger solid solubility of less than 0.0025%, and a low melting point of sodium (97.8°C). When sodium is present in the alloy, it adsorbs to the dendrite surface or grain boundary during solidification, and crystals are processed during thermal processing. The sodium on the boundary forms a liquid adsorption layer, and when brittle cracking occurs, a NaAlSi compound is formed, no free sodium is present, and no "sodium embrittlement" occurs. When magnesium content exceeds 2%, magnesium captures silicon and free sodium precipitates, resulting in "sodium embrittlement." Therefore, high-magnesium aluminum alloys are not allowed to use sodium salt flux. The method of preventing "sodium embrittlement" is chlorination, which causes sodium to form NaCl into the slag, adding helium to form Na2Bi into the metal matrix, and adding cerium to produce Na3Sb or adding rare earth can also play the same role.
Effect of Alloying Elements and Impurities in Aluminum on Properties
1 Effect of alloying elements