Too young. There are also many ways to unlock the aluminum alloy, such as foam aluminum.
How does aluminum foam unlock the aluminum alloy for vehicles?
Aluminum foam history
In the car circle, there is such a material. Like foam, it has high porosity, high specific surface area and strong damping and damping. Like metal, it has high specific strength, high specific stiffness, high temperature resistance and light weight. It is simply a dreamer of the carmaker.
But you are not dreaming. As early as the late 1940s, the United States took the lead in researching this material, and in 1951 scientist Elliot took the lead in the successful production of aluminum foam.
Aluminum foam is a lightweight porous metal material containing numerous bubbles in an aluminum matrix. It also has the characteristics of metal phase bubbles and is a physical functional material with broad application prospects.
Main structural features
(1) The hole structure is adjustable. Can be divided into two cases: one has an independent pore structure, scattered bubbles or hollow particles are distributed in the metal matrix (some call it sponge aluminum); the other is a porous structure with a through (some people call it Honeycomb aluminum).
(2) The aperture is large. The range of variation is 0.1-10.0mm (the pore diameter of the porous metallurgical metal powder is not more than 0.3mm).
(3) The void rate is high. The range of variation is 40% - 90% (the general powder metallurgy porous metal void rate is not more than 30%).
(4) The density is small. The variation range is 0.2-0.9/cm3 (only 1/10-1/3 of the same volume of aluminum).
However, this material is difficult to control in the foaming process, bubble size and uniformity, and it is very difficult to produce. It was not widely used at the time, and the manufacturing and application of foamed aluminum has been stagnant for more than 40 years. . Until the end of the 1980s, Japan's Kyushu Institute of Industrial Technology improved the production technology of aluminum foam, and the international development of foam aluminum materials again.
The first World Foam Metals Conference, held in Bremen, Germany in 1999, was a milestone in the rise of foam aluminum. Since then, foam aluminum has really moved from behind the scenes to the front of the stage, and the degree of industrialization has become higher and higher. It is no longer a scientific research material in the laboratory.
Main performance characteristics
High damping shock absorption performance and impact energy absorption rate: damping performance is 5-10 times that of metal aluminum. When the foamed aluminum having a porosity of 84% is changed by 50%, it can absorb energy of 2.5 MJ/M3C or more.
Good acoustic function: 1. Sound insulation performance (closed hole): When the sound frequency is between 800-4000HZ, the sound insulation coefficient of closed-cell foam aluminum is above 0.9. 2. Sound absorption performance (micro-through holes and through-holes): When the acoustic wave frequency is between 125 and 4000HZ, the sound absorption coefficient of the through-hole foam aluminum can be up to 0.8, and the average sound absorption coefficient of the octave is over 0.4.
Excellent electromagnetic shielding performance: When the electromagnetic wave frequency is between 2.6-18GHZ, the electromagnetic shielding amount of foam aluminum can reach 60-90dB.
Good thermal performance: Through-hole foamed aluminum has good heat dissipation under forced convection due to its pores communicating with each other. Does not burn and has good heat resistance. Good corrosion resistance, weather resistance, low moisture absorption, no aging, no toxicity.
Easy to process: easy to cut, drill, and bond; can be bent into a desired shape by molding; can be surface treated with organic or inorganic paint; can be skinned on both sides to form a large-sized lightweight, high-stiffness board.
Easy to install: foam aluminum can be installed in high places without mechanical lifting equipment, such as ceilings, walls and roofs, which can be mechanically or directly connected and fixed by screws, or glued to the wall with adhesive. Or on the ceiling.
Metal sheet - foam aluminum - the "sandwich" structure formed by sheet metal inherits the excellent properties of aluminum foam and has high flexural strength. It can be used as a high-strength structural part for new building materials and rolling stock.
Foam aluminum preparation method
There are more than 20 kinds of foam aluminum preparation processes, and the fields involved are very wide. However, for the automotive industry, the price of foam aluminum is not low, the processing technology is complicated, and the stability and reproducibility of various preparation processes are not very high. The problem of unevenness in the pore structure has not been completely solved.
The preparation of aluminum foam is mainly a solidification method, a sintering method, a deposition method, etc., wherein the solution foaming method is relatively simple, the pores are controllable, and the cost is low, and it is suitable for large-scale production of large-sized aluminum foam materials.
The use of aluminum foam in the automotive industry
Because foam aluminum has the characteristics of light weight, high specific strength, high specific stiffness, damping damping, sound absorption and heat insulation, battery shielding, etc., it is used in aerospace, high-speed chips and building materials. In recent years, this material has been used. Gradually entered the automotive field.
One of the classic applications of aluminum foam is the foam aluminum sandwich structure. Due to the combination of the properties of aluminum foam and metal sheets, the strength of the structure is better, the stiffness is increased by more than 2 times, the damping and collision resistance are improved by more than 3 times, and the quality is improved. Greatly reduced.
OME has designed a car with a foam aluminum sandwich panel structure that reduces the weight by 25% in the same structure.
According to reports, if aluminum foam parts are used instead of traditional automobile castings, the quality can be reduced by more than 50% without changing the strength of the parts.
Previously, BMW, in conjunction with the Australian Light Metal Performance Research Center (LKR), developed a foam aluminum structure engine bracket that reinforced the mechanical stiffness and thermal energy while enhancing frame rigidity and improving frame stability.
The German Kaman Automobile Company uses the sandwich composite foam aluminum to make the top cover of the Ghiaroadster. When the quality is reduced by 25%, the rigidity is about 7 times larger than the original steel components. It is really a stone and two birds.
When aluminum foam is used as an energy absorbing buffer structure, it is mostly applied to the energy absorbing box, the door beam structure and the bumper, and can achieve the purpose of buffering energy absorption. For example, foam aluminum is used as a core to make a car bumper, which has the function of absorbing impact kinetic energy. Since the rebound rate is small (less than 3%), secondary collision damage can be effectively avoided.
Let’s talk in more detail about some of the more unfamiliar things:
Energy absorbing box
The energy absorption capacity of the filling structure is greater than the sum of the energy absorbed by the energy absorbing box and the foam aluminum alone, and due to the isotropy of the aluminum foam, a good energy absorption can be obtained in the offset collision.
With the improvement of people's safety awareness, the concept of pedestrian safety has gradually taken shape. This structure can completely absorb all the energy that the vehicle hits at a speed of 15Km/h, and is able to protect pedestrian safety.
On the endothermic sound insulation, aluminum foam can also have an immediate effect. For example, it is used in the bus silencer.
The passenger car foam silencer and the foam aluminum sound absorbing plate are fire-resistant and can be applied to the exhaust gas temperature of nearly 600 °C. The noise reduction effect is 2 - 3 times of the impedance type muffling inner core and the parallel resonance muffling inner core muffler, and the weight is reduced by about 1/3.
In addition, the use of foam aluminum material to make car floor, space, door sandwich panels, etc. can also achieve the effect of sound insulation, isolation.
As the cover of the largest area on the car, the car top cover has always been a headache for manufacturers. The foam aluminum sandwich panel has a thickness of only about 2 mm, the rigidity is 7 times that of the steel roof, and the weight can be reduced by more than 50%.
Expectation for the future
Of course, seemingly perfect things always have the disadvantage of being helpless. At this stage, the advantages of aluminum foam are not superior to the high cost.
In the future, the use of a separate foam aluminum structure in a car may encounter bottlenecks, but it may be instructive to combine this material with other materials such as metals, polymers, and the like.
For example, the combination of aluminum foam and aluminum alloy or carbon fiber composite material can alleviate the disadvantages of high cost, brittleness and easy fracture of carbon fiber material to a certain extent, and at the same time, good thermal insulation mute and high temperature resistance can be obtained.
The reverse is also true. The application of carbon fiber as an auxiliary material in foamed aluminum is also promising for improving the performance of aluminum foam itself. Now there have been some researches on carbon fiber reinforced aluminum-based foam materials. The experimental results also show that on the basis of maintaining the original function of foam aluminum, the physical properties of the materials are further improved, and finally high energy absorption, damping shock absorption and pores are obtained. A foamed aluminum material with good wall toughness.
How to obtain a better sandwich structure, strengthen the bonding between aluminum foam and other materials, strengthen the performance characteristics of each material, or seek a new structure, such as multi-layer sandwich structure, etc. is also a better s Choice.
In short, although the research on aluminum foam has been deepened and applied in many other industries, it is far from being fully mature for the automotive industry. Currently, it is only used on some automotive parts. However, as a material with excellent performance, its application is far more than this. In the future, the combination of aluminum foam and various materials will be a trend.
As a kind of excellent material, aluminum foam should have a higher position in the automotive field. In the modern automobile industry where aluminum alloy is popular, it should receive more attention. Solving its cost and unity, finding a better composite method of structure and materials may be the new development direction of this material.