【正文】 oduction. Magnesium alloy in the automotive application increased year by year, is expected in the next 20 years, the amount of magnesium on the car will be more than 100kg per vehicle, is the current use of 30 times. Magnesium will bee a new material for most structural parts of the car.3 engineering plastics and posite materialsEngineering plastics and posites are another important type of automotive lightweight material. Compared with the general plastic, engineering plastics have excellent mechanical properties, chemical resistance, heat resistance, wear resistance, dimensional stability and other characteristics, than the replacement of metal materials and light energy when molding less. At present, most of the engineering plastics used in the body inside and outside the trim, such as body fender, rear panel, dashboard, door panels, ceiling, side liner lining, door anticollision, handrails, windows, heat Cover, and so on. Compared to metal can be reduced by 40%, and can withstand erosion and slight collision, in the case of lowspeed collision without maintenance, from the manufacturing point of view pared to metal has greater freedom of modeling to enhance, but also facilitate the integration of parts, from the pedestrian protection Consider, is also ideal material. Ford developed the LTD test car, plastic body after the lightweight aspects of the obvious results, the vehicle weight loss of up to 300kg or more. The scope of application of engineering plastics in automobiles is expanding from interior parts to exterior parts, bodywork and structural parts. The future development direction is to develop structural parts, reinforced plastic posites for exterior parts, high performance resin materials and plastics, and Will pay more attention to the recyclability of materials.Fiber reinforced plastic is a posite fiber and plastic posite materials. Commonly used is glass fiber and thermosetting resin posite material. This kind of posite material has the advantages of small density, flexible design, easy molding, corrosion resistance, heat insulation, impact resistance, antivibration, easy coating, high strength, high elastic modulus, mechanical properties similar to metal materials, Under certain conditions, there is a metal sheet can not match the advantages of quality reduction and strength to achieve even more than the aluminum, while the overall cost is lower. At present in the car body has been widely used in the useful glass fiber reinforced unsaturated polyester chip molding pound (SMC) manufacturing body air deflector, the front fender and the front fender extension parts, headlamps, hood, Decorative pieces, tail plate, etc .。s body quality [5].China is a large resource of magnesium, magnesium ore products and more species, rich reserves, accounting for the world39。Specific strength and specific stiffness of aluminum metalbased posite materials research and development success for the further development of automotive lightweight provides a way. Germany39。s aluminum processing industry and the automotive industry to the world39。s car body with aluminum alloy up to 162kg, steel body weight loss of about 40%. And China39。 the latter excellent shape, Mainly used in the body plate and other plex parts of the shape, such as car floor structure and so on. At present, low density, high strength, high elastic modulus and superplasticity of the AILi alloy and aluminum antivibration plate, etc. has been gradually applied to the body.Aluminum alloy has good formability. Aluminum alloy body structure mainly used aluminum extrusion profiles as the main body of the space frame structure, generally with medium and strong aluminum can meet the requirements. Extrusion profiles are mainly hollow materials, in addition to light weight, high rigidity, high temperature strength, heat resistance, corrosion resistance is also very good, and can be welded, surface treatment and bending processing. The current aluminum body is made of thickwalled forged aluminum beams, and is more advantageous than stamping thin steel in terms of structural strength and stiffness, and the overall stability of the mechanism is better. Lightweight and highstrength aluminum body more solid than the traditional steel body, and do not worry about corrosion caused by the reduction of strength [3].From the aluminum panel application development trend, high strength, good forming processability, excellent surface quality aluminum plate will replace the steel plate as the main mat