Automotive lightweight intelligence has become a new trend in the global automotive industry technology development. In recent years, with the development of the global trend of energy saving and emission reduction pressure, many countries have formulated strict regulations of passenger car fuel consumption standard, more stringent requirements on the emission of CO2 passenger car fuel consumption and the lightweight of automobile is the development trend of the world car. Especially in China, by 2020, the fuel consumption of automobiles is significantly lower than that of other countries, and the pressure of fuel emission is greater. Reducing vehicle weight is the most effective way of vehicle lightweight. Car lightweight is for the car "lean", on the basis of ensuring stability and upgrading performance, energy-saving design of the various parts, continuous optimization of the car model. Experiments show that if the vehicle weight is reduced by 10%, fuel efficiency can be increased by 6% - 8%; vehicle weight decreased 1%, fuel consumption can be reduced by 0.7%; vehicle kerb weight decreased by 100 per kg, 100 km fuel consumption can be reduced by 0.3 - 0.6 liters.
The light weight trend of automobiles
Tsinghua University professor Ouyang Ming high representative of energy-saving and new energy vehicle development strategy advisory committee has been released on the content of energy-saving and new energy vehicle technology roadmap for the development of lightweight technical ideas of the proposed roadmap, mainly divided into three stages to achieve auto weight loss year by year.

The first stage was 2016 - 2020, the weight loss of the whole vehicle was 10% less than that in 2015. Focus on the development of ultra high strength steel high strength steel and advanced technology, including material properties, development of the lightweight design method, molding technology, welding process test and evaluation methods, to achieve high strength steel in automotive applications proportion reached more than 50%, to carry out Aluminum Alloy stamping plate production technology research and practice in the body, connecting different technology research material.
The second stage is 2021 - 2025, the vehicle weight reduction is 20% compared with the 2015. In the third generation automobile steels and Aluminum Alloy technology as the main line, to achieve a variety of materials such as steel aluminum hybrid body, a wide range of applications of aluminum body, realize the Aluminum Alloy cover and Aluminum Alloy parts of the mass production and industrial applications, also increase the development of parts of magnesium alloy and carbon fiber composite material manufacturing technology, application increase the proportion of magnesium alloy and carbon fiber parts, aluminum bicycle reached 350kg.
The third stage is 2026 - 2030, the vehicle weight reduction is 35% compared with the 2015. Magnesium alloy and carbon fiber composite technology are mainly developed to solve the problem of recycling of magnesium alloy and composite materials, and achieve a wide range of applications of carbon fiber composite body and carbon fiber parts, breaking through the technology of complex parts forming and the connection technology of dissimilar parts. Bicycle with magnesium alloy reaches 45kg, the use of carbon fiber weight accounted for 5%.
According to statistics, in 2016, the amount of magnesium alloy used in China was only 7.3kg, and there was a huge gap between the single magnesium alloy and the target 45kg of 2030. Magnesium alloy has broad market potential and has unlimited potential in the future.
Properties and advantages of magnesium alloy:
Low density
The density of die cast magnesium alloy is only 2/3 of aluminum alloy. The 1/4, specific strength and specific stiffness of steel are better than those of steel and aluminum alloy, which is much higher than that of engineering plastics. So die casting magnesium alloy is a fine lightweight structural material that can compete with the above materials in many applications.
Good vibration absorption
It is beneficial to vibration reduction and noise reduction. For example, under the stress level of 35MPa, the attenuation coefficient of magnesium alloy AZ91D is 25%, and the aluminum alloy A380 is only 1%. At the 100MP stress level, the magnesium alloy AZ91D, AM60, and AS41 are 53%, 72% and 70% respectively, and the aluminum alloy A380 is only 4%.
High dimensional stability
The dimensional instability of the magnesium alloy die casting is reduced due to the change of ambient temperature and time.
High thermal conductivity
The thermal conductivity of magnesium alloy (60 - 70W/m-1 K-1) is second only to the aluminum alloy (about 100 - 70W M-1 K-1), so the thermal diffusivity is good.
No magnetic, can be used for electromagnetic shielding.
Good wear resistance
Magnesium alloy also has good damping coefficient, damping capacity is greater than aluminum alloy and cast iron, it can reduce noise for shell, for seat and hub, it can reduce vibration and improve the safety and comfort of vehicle.  Magnesium alloy has the advantages of light weight, strong shock absorption, good casting performance, high automation production capacity and high service life and stable size. As the lightest engineering material, magnesium alloy is not only the most suitable material for casting automobile components, but also the most effective lightweight material for automobiles.

Current status of magnesium alloy automotive die casting industry
The lightweight development of automobile makes the demand for magnesium aluminum and other light alloy castings increase year by year. Since 1990, the automotive magnesium has been developing rapidly at an annual rate of 20%, and magnesium alloys have become an important field in the development of automotive materials technology. Die cast magnesium alloy is especially suitable for recycling economy and energy saving, low carbon and clean production requirements due to its advanced recycling and less chip free technology. It plays a leading role in the process of lightweight development. All the major auto parts manufacturers have actively grasped the development time, and have invested in the production and development of magnesium alloy automobile die casting. According to the analysis report of China magnesium alloy automotive die castings industry analysis, in 2015, China magnesium alloy automotive die castings industry demand reached 149 thousand tons, an increase of 23.12% over the same period last year. At present, domestic and foreign automobile enterprises are dedicated to the study of accounting for a large proportion of body weight (about 30%), engine (about 18%), transmission system (about 15%), walking system (about 16%), wheels (about 5%) magnesium alloy such as steel or aluminum parts.
Considering the amount of magnesium alloy used in China, the market capacity of China's magnesium alloy die castings industry will reach 229 thousand tons in 2017, and the market capacity will reach 660 thousand tons by 2022, the annual compound growth rate will reach 23.5%.
The global car use of magnesium is low, and the expansion potential of automotive magnesium alloys is strong. All the time, all aspects of high strength steel, Aluminum Alloy, engineering plastics and other lightweight materials are widely used in automobiles and auto parts manufacturing, and magnesium alloy for a variety of reasons have not been popularized and used magnesium alloys are mainly used in the instrument panel bracket, steering bracket, engine cover, steering wheel, seat bracket, car the inner door panel, transmission housing etc.. At present, every vehicle in North America uses magnesium alloy 3.8kg, Japan is 9.3kg, and every vehicle in Europe PASSAT and Audi A4 reaches 14kg, and the average car consumption per domestic vehicle is only 1.5kg.

Application of magnesium alloy in automobile lightweight
Internal structure of automobile
Although the corrosion resistance of magnesium alloys is poor, anti-corrosion is not a major consideration for the internal structure of the automobile, so magnesium alloys have been widely applied in the automotive internal structure, especially in the dashboard and steering structure. It is reported that the first magnesium alloy dashboard pillar was produced by the General Company in 1961, compared with the same components produced by the zinc alloy die-casting.