Aluminum is a silver-white light metal, relatively soft, density 2.7g/cm3, melting point 660.4℃, boiling point 2467℃, aluminum and aluminum alloys have many excellent physical properties, has been very widely used. Aluminum has good reflection performance of light, reflecting ultraviolet light is stronger than silver, the purer aluminum is, its reflection ability is better, and the method of vacuum aluminum plating is commonly used to make high-quality mirrors. Vacuum aluminized film combined with polysilicon film becomes a cheap and lightweight solar cell material. Aluminum powder can maintain a silvery luster, often used to make paint, commonly known as silver powder. Pure aluminum conducts electricity very well, second only to silver and copper. In the electric power industry, it can replace part of copper for wires and cables. Aluminum is a good conductor of heat. It can be used to make various heat exchangers, heat dissipating materials and civil cookers in industry. Aluminum has good ductility, can be drawn into a fine wire, rolled into a variety of aluminum products, but also can be made into thinner than 0.01mm aluminum foil, widely used in packaging cigarettes, candy, etc.. Aluminum alloy has some better properties than pure aluminum, which greatly expands the application range of aluminum. For example, pure aluminum is soft, when a certain amount of copper, magnesium, manganese and other metals are added to aluminum, the strength can be greatly improved, almost equivalent to steel, and the density is small, not easy to rust, widely used in aircraft, cars, trains, ships, artificial satellites, rockets manufacturing. At -196 ° C, some steel is as brittle as glass, while some aluminum alloys increase in strength and toughness, making them cheap and lightweight cryogenic materials that can be used to store liquid oxygen and hydrogen for rocket fuel.