The inspirability of metal is determined by the binding ability of metal and gas. The binding force of the metal and gas is different, and the solubility of the gas in the metal is also different.
Metals and alloys with high vapor pressure can reduce gas content due to evaporation and adsorption. The alloy elements with large binding force with gas will increase the solubility of the alloy. On the contrary, the elements with less binding force with gas increase the solidification temperature range of alloy, especially the elements with lower solid-phase line temperature, easy to make the ingot porosity.
Copper, silicon, manganese and zinc all reduce the gas solubility in aluminum alloys, while titanium, zirconium and magnesium do the opposite.
The higher the temperature of molten metal, the faster the thermal movement of metal and gas molecules, and the diffusion rate of gas inside the metal also increases. Therefore, in general, the solubility of the gas in the metal increases with the temperature.
Aluminum alloy basic status code
F free processing state is suitable for products with special requirements for work hardening and heat treatment conditions during the molding process, and the mechanical properties of the products in this state are not specified (uncommon).
O Annealing state suitable for fully annealed products with the lowest strength (occasionally)
The work hardening state is suitable for products with increased strength through work hardening, and the product can undergo (or may not undergo) additional heat treatment to reduce the strength after work hardening (generally non-heat treatment strengthened materials).
W solid solution heat treatment state An unstable state, only applicable to alloys that age naturally at room temperature after solid solution heat treatment, the state code only means that the product is in the natural aging stage (uncommon)
The T heat treatment state (different from the F, O, and H states) is suitable for products that have been stabilized by work hardening (or not) after heat treatment. The T code must be followed by one or more Arabic numbers (generally for heat-treated strengthened materials) The status code behind our common non-heat-treated strengthened aluminum alloys is generally the letter H plus two digits.
Effect of alloy composition on mechanical properties of 6061-T6 aluminum alloy
The main alloying element of 6061 aluminum alloy is magnesium and silicon and forms Mg2Si phase. If it contains a certain amount of manganese and chromium can neutralize the bad effects of iron? Sometimes a small amount of copper or zinc is added to improve the strength of the alloy. There is also a small amount of copper in the conductive material to offset the adverse effects of titanium and iron on the electrical conductivity. Zirconium or titanium can refine the grain and control the recrystallization structure. In order to improve the machinability, lead and bismuth can be added. The main reinforcer Mg2Si is soluble in aluminum and the alloy has the function of artificial age hardening. Therefore, in order to have better mechanical properties, qualified chemical composition is the premise, especially the formation of the main strengthening phase Mg2Si, we must ensure that the chemical composition meets the requirements of the national standard, in order to achieve good mechanical properties after post-treatment.
Other factors in the casting of aluminum alloy profiles such as aluminum rods
Because there is an oxide film on the surface of the metal melt, and it is dense, it hinders the diffusion of gas to the interior of the metal, and the dissolution rate is greatly slowed down. If the oxide film is destroyed, it will inevitably accelerate the metal's absorption of gas. Therefore, in the process of melting casting, any operation that destroys the oxide film on the surface of the melt is unfavorable.
For any chemical reaction, the time factor is always favorable for a reaction to proceed continuously until it reaches a state of saturation for the gas dissolved in the metal. Therefore, the longer the exposure time in any case, the more inhalation. In particular, the melt is exposed to high temperatures for a long time, which increases the chance of inhalation. 6061 aluminum sheet in the melting process, always strive to shorten the melting time to minimize the gas content of the melt.