Magnesium is a very abundant metal, but is produced in small quantities. The amount of magnesium produced each year is about 400,000 metric tons. The amount of aluminum produced each year is about 22,000,000 metric tons. Both metals were isolated and identified by Sir Humphrey Davy within a year of each other.
Magnesium is the lightest structural metal. Based on structural metal occurrence in the Earth's crust, magnesium is the third most abundant after aluminum and iron. Silicon is the most abundant element, but it is not a structural material. Based on the magnesium in brine deposits, salt lakes and the oceans, magnesium is by far the most abundant of all metals. There are 6,000,000 tons of magnesium in a cubic mile of seawater. There are 330 million cubic miles of seawater according to the Scientific American.
Magnesium has properties that enable it to be used in many areas. Its very light weight makes it especially attractive to aerospace and to automobile industries. However, magnesium has struggled for acceptance for many years, mainly due to a high price when compared to aluminum. That wide variation of price is being overcome and magnesium is now ready to be more widely used to benefit mankind and the environment.
Magnesium's density is 1.74 compared to aluminum at 2.7. There are other basic inherent advantages with the use of magnesium, not the least of which is greater rigidity and a much higher damping capacity.
Of the total amount of magnesium metal used in industry on a worldwide basis in 2002, approximately one-half went to aluminum alloying and desulfurization of iron and steel. The magnesium industry did very little work and invested very little money in these applications. Most of the research and development was done by the end-user company.
Most of the major uses of magnesium in automobiles were developed and promoted by engineers and designers employed by the auto companies. That included the earlier use of magnesium in the Volkswagen Beetle, the world's most successful car, with approximately 25 million vehicles being built. Construction continues in South America and Mexico. The Beetle used approximately 44 pounds (22 kg) in each car. Magnesium was specified by Porsche in the original car and has remained that way. (Porsche first worked with a magnesium engine in 1928.)
The potential for magnesium applications is limitless. Magnesium development needs some long-range vision, technical intelligence, and lots of work and money. Unfortunately, many of the producers are fighting for survival and it is difficult to justify the investment of large amounts of money in research and development. But without the vision and investment, plus a strong marketing effort, magnesium applications will continue to be slow in developing.
The great immediate future for magnesium remains in the world autos. There is a need for light weight and there are many millions of cars produced each year. However, the auto industry has changed and it has less designers and materials people on companies' staff than was the case. To get more magnesium usage in automobiles, the magnesium industry must take a much more pro-active approach to the auto companies. In many cases, the final design decisions are being left to the Tier 1 suppliers. The auto companies are becoming specifiers of components that they will assemble. Much of the component supply is based on just-in-time delivery.
Any new magnesium use must meet some basic review criteria:
1. The cost of the finished product must be competitive. This includes the direct cost and the overall usage cost. For example, a lightweight part on a car may cost more than aluminum, but the lighter weight may have many other advantages that would add value to the use of the magnesium part.
2. The application must be reducible to efficient manufacturing processes. This includes casting or fabrication rates, scrap, and finishing and assembly operations.
3. Resistance to corrosion. Magnesium occupies a very high position on the table of electrochemical activities. This means that it tends to corrode faster than some other materials. Alloy development, assembly research, and coating technologists must continue to work to lessen these problems.
4. Flammability. While magnesium does not burn unless it melts, finely divided powder and shaving created in fabrication operations can catch fire. In any case, it is an area that must be constantly addressed. As long as science teachers in high school classes continue to burn pieces of magnesium ribbon, the image of the bright white fire will far surpass any knowledge of the fire resistance of solid magnesium.
5. Commonality. Aluminum objects exist everywhere. There are a million examples of aluminum use. There are very few visible examples of magnesium use. Many people go through their lives without ever coming into contact with magnesium unless it be in vitamin supplements or Milk of Magnesia. This has changed to some extent with the increased use of magnesium in computer cases and cellular phones.
Magnesium can be utilized in any item that is used in a repetitive fashion by human labor. The use of magnesium in chainsaws, nail guns, electric drills, plasterers, and brick layers tools is greatly advantageous to the man who works with the tools all day.
Magnesium was used in ladders for many years, for example, by fire departments. When the price of magnesium increased dramatically in the 1970s, many users crossed over to aluminum because of the cost difference.
Magnesium producers must realize that magnesium will only become a wider used material if information and data on the metal and its alloys is readily available. Without this step forward, magnesium cannot experience the interest and growth that its marvelous properties warrant.
Magnesium alloys that will withstand higher temperatures are being developed. This type of work, promoted by the magnesium researchers in many areas, is now getting closer scrutiny from the auto manufacturers for engine blocks and transmission housings. The recent announcement by Mercedes-Benz of a new 7G-TRONIC seven speed, automatic transmission that will be standard on the E500, S430, S500, CL500, and SL500 cars from Autumn 2003 was of great interest since the housing will be in magnesium, enabling the change from 5-speed to 7-speed without a weight penalty.
At present, approximately 1 million GMT800 full size trucks and sport utility vehicles (SUV) are produced annually. These vehicles have two magnesium transfer cases (total weight 7 kg) per unit. At VW in 2002, about 600 manual transmission cases were produced daily for the VW Passat and the Audi A4/A6. Magnesium transmission cases are also used in the VW Santana produced in China. These are all manual transmissions and the temperature of operation is below 125?C so a standard AZ91 alloy can be used. Automatic transmissions run at higher temperatures and new alloys with better creep resistance at the higher temperatures are needed. Some automatic transmissions are starting to be produced for production model cars in magnesium.
German carmaker Audi, a unit of German vehicle manufacturer Volkswagen, plans to launch on the Spanish market its all-road vehicle Audi V8 Quattro, it was reported on May 5, 2003.
The car is equipped with a 4.2 liter, 300 hp engine, and can develop from 2,700 to 4,600 revolutions per minute (RPM). The model has five-speed, Tiptronic automatic transmission with Dynamic Shift Programme (DSP), which allows an acceleration from 0 to 100 km/h in 7.2 seconds. The car can reach a maximum speed of 240 km/h. Audi V8 Quattro will be introduced on the Spanish market at a price of $76,500 (67,820). [Editor's note: Through the use of magnesium components, the engine weight of Audi V8 Quattro model has been reduced some 5 kg compared to other Audi eight-cylinder engines. Tiptronic is a registered trademark of Audi. It is a special kind of transmission, which combines the convenience of the automatic transmission with the dynamics of a manual transmission. The driver can switch from automatic to Tiptronic at any time while driving. In both modes, gear shifts take place with no power interruption.
When there are 40 million cars produced per year, then the addition of 20 kg on 25% of the vehicle production would require 200 million kg of magnesium or 200,000 tons of magnesium alloy. This would require a 50% increase in the total world production of magnesium.
The automotive use that has received the greatest worldwide acceptance is the steering wheel. Nearly one-half of all vehicles produced in 2002 used a magnesium die-casting for the steering wheel. The reason for magnesium is to keep the weight down as the wheel is designed to contain an air bag container. The wheel is also made of an alloy that will deform and not break on impact. This same design parameter has been used when designing the ignition mechanisms into the steering column. In crash testing, it is important that the steering column go up and away from the driver's body. The lighter weight of the assembly helps in this.
Georg Fischer AG of Switzerland has a contract for magnesium steering column components that will be used in the 2004 Ford 500 sedans, Freestyle sports wagons and Mercury Montegos. Parts will be produced by die-casting at a North American location. Fisher will die-cast magnesium steering/ignition lock housings for Visteon, a Tier 1 supplier that is the system designer.
Increasing the use of magnesium in cars is not easy. Over the years, magnesium and aluminum (and some plastic) have switched and swapped places as the preferred material for some auto parts. In recent times, hydro-formed steels and dual-phase steels have also fought to maintain the dominant position of steel in the automotive industry. However, in the past year or less, magnesium has again moved up. Taking advantage of the light weight and the reduction in primary metal prices, the die-casters have continued to work with automotive engineers and designers to keep magnesium in the cars.
Part of the magnesium problem has been the close review given (benchmarking) to instrument panel support beams (IP) by companies like GM. The close scrutiny using Toyota and Nissan as the comparison cars shows that the Japanese do not use magnesium, but use tubular steel as the best low cost structural material for the IP.
It is now reported that magnesium has been made the go-to material of choice with the GM plastic NAO '04 Model Year Epsilon IP structure changing to magnesium (from Lunt and Meridian) early last year. The '04 Impala Monte Carlo x-car will revert from tubular steel to magnesium IP from Meridian. The next release of the mid size GM SUV for the '06 model year will revert from magnesium with a steel extension to all magnesium IP (source not yet determined).
It was reported also that magnesium will be used in the IPs in the next generation Pontiac Grand AM mid-size car in '05 model year. Magnesium is also being considered for use in the frames of the retractable hardtop roofs for convertible models of the Grand Ams.
One of the largest magnesium die-castings is the one-piece instrument panel (IP) for the GM G-van (GMC Savana and Chevrolet Express). The finished IP weighs 12 kg as opposed to the 18 kg in steel. The part also offers better crashworthiness and cost savings due to design consolidation (25 parts in magnesium design vs. 67 parts in steel).
The IP die-castings for recent models GM H-car, (Pontiac, Bonneville, and Buick LeSabre) weigh 5 kg and are made by Meridian of Canada. It was also reported recently that the new Porsche Carrera GT will use a magnesium console cast by Stolfig.
Ford has reportedly decided on magnesium for the Front End Support Assemblies (FESA) for light-duty trucks. Magnesium was said to have beat out hydro-formed steel tubular steel, extruded aluminum, and molded plastics composites. Die-cast AM60 was the final choice. The reason for the magnesium success was the projected weight and cost-savings, size and space considerations, performance and dimensional control. The assemblies will first be incorporated into the 2004 standard-size F-150 pickup trucks. Estimates say the parts could use 5 million kg of AM50 per year.
The finished FESA castings will weigh more than 6 kg each. This is more than the total average of all magnesium used in North American cars. This is the first application in a structural part that will support the radiator and other front-end components. Castings will come from Meridian with magnesium from Norsk Hydro. Ford reviewed the aluminum supports used by GM and looked at plastics parts from Europe before deciding on the magnesium.
Magnesium has been used in automotive seats. First used by Mercedes as an integrated seat structure with a three-point safety belt in the SLRoadster. The seat was made up of five parts with a total weight of 8.5 kg. It was chosen over steel, aluminum, and plastics. The alloy used was AM50 and AM20. Now it is reported that the Alfa Romeo 156 uses a magnesium seat in a two-piece design.
GM has offered magnesium wheels for the Corvette since 1998. There is a very great interest in magnesium wheels for everyday vehicles. One advantage is the fact that the reduction in unsprung weight makes it much easier to reduce total car weight. The group that can develop an economical magnesium wheel that will meet Detroit standards will have a great potential to develop a very profitable business. The new Porsche Carrera GT will be built using magnesium wheel rims from BBS in Germany. No weights were given. There will be about 1500 of the cars produced.
Application development remains the key to the expansion of magnesium production. Many of the newer companies have stepped up to join and/or replace some of the old reliables in this type of research and development. Many countries with companies that produce and/or use magnesium are also assisting in the promotion of magnesium research and development.
About the Author
Peter Howard is a freelance writer for Magnesium .
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