The magnesium alloy, known as AM-SCI, can reduce the weight of vehicle engine components by up to seventy per cent, resulting in improved fuel efficiency and less pollution.
The new material has already been cast into an engine block designed by leading European engine design company, AVL List. The new engine, the AVL Genios LE, is installed in a three-cylinder Volkswagon Lupo car currently being road tested in Austria.
The project’s team leader Colleen Bettles says: “The new 14 kg engine is a three-cylinder diesel, a fuel that demands higher performance than petrol engines. The result is an engine that is more than 33 per cent lighter than existing lightweight aluminium engines and about 75 per cent lighter than cast iron.
“Magnesium alloy engine blocks will be featherweights compared with the cast iron that ruled for most of the 20th century and is still used for the majority of internal combustion engines.”
CAST, the Cooperative Research Centre for Cast Metals Manufacturing in Queensland, established and supported under the Australian Government’s cooperative research centres program, has been conducting research on alloy development for more than four years in partnership with the Australian Magnesium Corporation (AMC).
According to the CEO of CAST Professor David St John: “Developing a magnesium alloy that can be used in the high temperature conditions found in modern car engines has been the goal of researchers for many years.
“We achieved this by bringing together a team of Australia’s best researchers in the field of magnesium alloy development.”
CAST’s alloy development research team was sourced from CSIRO, The University of Queensland and Monash University in Victoria to provide an alloy with the necessary thermal and mechanical properties for use in the engine block.
Magnesium has an excellent strength to weight ratio, high shock and dent resistance and dampens noise and vibrations significantly more than aluminium or steel.
To date, magnesium alloys have been used in vehicles for steering wheels, instrument panels and seat frames. However, it is the engine that makes the most significant contribution to the weight of a vehicle – the block alone is 20-25 per cent of the total engine weight.
The new alloy can be prepared and processed using standard techniques and is suitable for production of precision castings using a standard sand casting process. This makes it easy to substitute into cars.
According to Professor St John, the AMC project has closed down pending a review of projected cost over-runs. As a consequence, Australia is yet to enter the magnesium metal scene.
“We hope the project can be salvaged in a restructured form. While there is no doubt that this industry will have a longer gestation period than the proponents envisaged, it is a key building block to Australia’s future manufacturing base, in particular the automotive industries.”
A prime role for CAST is to support the growth and competitiveness of the Australian light metals industry through its research, education and commercialisation activities. Just as Australian industry participates in the rapidly developing global economy, CAST also operates globally and works with partners around the world.
The commercialisation of CAST’s new die coating technology, CASTcoatTM is well advanced and other opportunities for expansion have been identified.
CAST’s partner organisations ensure that CAST is well equipped to tackle the major issues limiting the adoption of light metals technologies by manufacturing industries and their customers. CAST outlines its major products:
Magnesium for crash structures
If you drive a car manufactured from steel you probably feel safer than if your car was manufactured from plastic or rubber, however there are certain situations where steel can be a problem in car crashes.
Some steels become brittle when deformed at high speeds, which means that the steel can break in the event of an automotive accident. When this deficiency was first recognised, the hunt began for a new metal alloy that would not become brittle in crash situations.
Aluminium has almost no sensitivity to the speed at which it is deformed making it an obvious choice to substitute for steel in automobile frames. However, some magnesium alloys, like steel, are very sensitive to the speed at which they are deformed, but unlike steel they get stronger.
For this reason magnesium alloys have the potential to be used to design efficient energy absorbing structures that will protect people in the event of a car accident.
AM-SC1 – a new magnesium engine block alloy
To date, magnesium alloys have been used in vehicle components such as steering wheels, instrument panels and seat frames. Significant weight savings were achieved with the introduction of the aluminium block to replace cast iron and further reductions, of the order of 25 per cent, are possible if a magnesium alloy is used.
The difficulty with using current magnesium alloys in engine blocks is that they are either too expensive or do not have the right properties to withstand the demanding temperature and pressure conditions experienced in a modern engine.
It therefore became necessary to develop an entirely new magnesium alloy, which could be combined with a cost effective production process, so that a commercially attractive magnesium engine block can be produced. The result is AM-SC1.
Wrought magnesium alloys
The global market for wrought magnesium alloys is currently around 6000-7000 tonnes per annum. Extruded magnesium alloys offer potential competitive advantages over die-cast magnesium by virtue of higher yield, greater throughput, and lower specific investments required for extrusions.
However, magnesium alloy extrusions suffer in comparison with aluminium alloy extrusions because of a lower speed (approximately one third to two thirds that of aluminium alloys), and the higher raw material cost.
When weight-saving is taken into account, there is potential to realise gains over aluminium alloys of up to 25 per cent of the cost of a part if a new alloy can be produced with optimum extrusion characteristics.
The development of new extrusion alloys will lead to new application areas, and novel processing routes will lead to lower production costs for both conventional and new alloys.
Applied design corrosion research
The major activity of this project has been to coat magnesium alloys with numerous different surface treatments available commercially and compare their performance under standard test conditions (in this case a test developed by General Motors).
As part of this project the test itself was checked by slightly varying parameters such as spray composition and the length of various stages in the cycle.
Magnesium alloys in general have low corrosion resistance and they always act as anodes to most other metals if they are in contact with these metals. So, magnesium components are usually subjected to two kinds of corrosion attack: 1) general corrosion, and 2) galvanic corrosion.
Apart from many corrosion protection measures, the general corrosion of Magnesium alloys can be prevented to some extent through altering the composition or microstructure of the alloys. However, the galvanic corrosion performance is difficult to improve by changing the metallurgical and casting parameters alone.
It has been realised that galvanic corrosion is one of the main concerns in the application of magnesium alloys in the automotive industry.
There are several existing surface treatments and coating techniques that have been claimed to be able to provide various degrees of corrosion protection to magnesium alloys. The aim of this project is to develop an economical surface layer system that can be used in various service environments with improved corrosion resistance and other relevant properties.
Australian scientists at the Commonwealth Scientific & Industrial Research Organisation (CSIRO), have developed an industrial scale pilot plant to produce low cost magnesium sheet of exacting dimensions.
CSIRO’s magnesium sheet casting plant demonstrates large savings on the capital cost of conventional production.
CSIRO has been developing casting of magnesium alloy sheet since 2000. The plant produces ‘as-cast’ magnesium sheet of up to 600 mm in width.
An exhaustive proving program has demonstrated its technology is reliable, low-cost, efficient and suitable for both continuous and batch production, while producing good quality magnesium alloy sheet from a large range of conventional and new magnesium alloys.
Magnesium alloys are lightweight (with a density that is approximately two thirds that of aluminium alloys) and have the benefits of improved strength and stiffness, good damping characteristics, and are suited to welding, machining and casting.
Commercial quality sheet samples of 100-600 mm width and from 2.3-5mm thickness have been successfully cast in standard alloys along with new magnesium wrought alloys.
These samples were rolled down to 0.5-0.6 mm gauges, using a unique finish-rolling schedule developed by CSIRO specifically for cast magnesium alloy sheet.
Mechanical tests have confirmed the CSIRO magnesium sheet has the equivalent or superior properties to the conventional wrought magnesium sheet, and product prototyping shows a good performance of the sheet materials in press forming.
Magnesium alloys also have excellent shielding capability against electromagnetic interference, environmental stability, effective heat dissipation and are recyclable in a range of established foundry processes. Most of these properties make magnesium sheet ideal material for motor vehicle body panels, seat profiles, doors and even bumper bars.