Physical properties of aluminum

Aluminum is a metallic element, element symbol Al, is a silver white light metal. It's malleable.

Physical properties

In humid air, an oxide film can be formed to prevent metal corrosion. The aluminum powder, which has been treated with acid, burns violently in the air with heat and emits a blinding white flame.

Soluble in dilute sulfuric acid, dilute nitric acid, hydrochloric acid, sodium hydroxide and potassium hydroxide solution, insoluble in water, but can slowly react with hot water to produce aluminum hydroxide, relative density 2.70, elastic modulus 70Gpa, Poisson's ratio 0.33. Melting point is 660 ℃. The boiling point of 2327 ℃. It is widely used for its light weight, good electrical and thermal conductivity, high reflectivity and oxidation resistance. The aluminum used for daily dishes is usually called "fine steel" or "grade steel". Al thermal expansion coefficient at (room temperature) 25℃ 0.0000236mm/℃ or 23.6ppm* K-1.

First, the effect of aluminum on the microstructure and heat treatment of steel

(1) Aluminum has a strong affinity with oxygen and nitrogen, is the deoxy nitrogen fixing agent in steelmaking.

② Aluminum strongly reduces the austenite phase zone in steel.

(3) The affinity of aluminum and carbon is small, and there is generally no aluminum carbide in steel. Aluminum strongly promotes the graphitization of carbon. The graphitization of aluminum can be inhibited by the addition of strong magnetized elements such as chromium, titanium, vanadium and niobium.

(4) Aluminum refines the essential grain of steel and increases the coarsening temperature of steel grain. However, when the content of solid solution aluminum in steel exceeds a certain value, austenite grain is easy to grow and coarsening.

(5) Aluminum increases the martensite transition temperature of steel and reduces the residual austenite content after quenching, which is contrary to other alloying elements except cobalt.

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