Views: 1 Author: Site Editor Publish Time: 2022-07-20 Origin: Site
(3) Aluminum matrix composites
Aluminum matrix composites have low density, high specific strength and modulus, and good thermal fatigue resistance, but their application in automobiles is restricted by price and production quality control, and has not yet formed a large scale. At present, the test or use of aluminum matrix composites on connecting rods, pistons, cylinder bores, brake discs, brake calipers, transmission shaft tubes and other parts has shown excellent performance. For example, is it possible for Honda to successfully develop? The weight of steel wire reinforced aluminum matrix composite connecting rod is 30% lower than that of steel connecting rod, and the fuel economy of 1.2L gasoline engine can be improved by 5%; The quenched aluminum alloy powder and SiC powder (2% by weight) are mixed and extruded into a bar. The forged piston with this bar can reduce the weight by 20% due to its high strength and greatly improve the engine power; The weight of austenitic cast iron insert can be reduced by 20% by strengthening the piston head with aluminum matrix composite and canceling the first ring groove; The weight of aluminum composite brake disc is 50% lower than that of cast iron brake disc.
The density of magnesium is about 2/3 that of aluminum, which is the lightest metal in practical application. Magnesium alloy has strong vibration absorption ability, good cutting performance and good metal mold casting performance, which is very suitable for manufacturing automotive parts.
Most magnesium alloys are used in automobiles in the form of die castings. The production efficiency of magnesium die castings is 30% - 50% higher than that of aluminum. The newly developed pore free Diecast method can produce magnesium die castings that have no pores and can be heat treated.
The earliest example of magnesium castings used in automobiles is wheel rims. Examples of trying or applying magnesium alloys in automobiles include clutch housings, clutch pedals, brake pedal fixing brackets, instrument panel frames, seats, steering column components, steering wheel cores, gearbox housings, engine mounts, cylinder heads, cylinder head covers, etc. Compared with the traditional zinc steering column bracket, the weight of magnesium parts is reduced by 65%; Compared with the traditional steel steering wheel core, the weight of magnesium parts is reduced by 45%; Compared with the all aluminum cylinder head, the weight of magnesium parts is reduced by 30%; Compared with the traditional steel stamping and welding brake pedal support, the weight of the overall magnesium casting is reduced by 40%, and its rigidity is also improved.
The research of magnesium matrix composites has also made progress. The magnesium matrix composites obtained by using SiC particles as reinforcement and liquid stirring technology have good performance and low production cost. The tensile strength, yield strength and elastic modulus of the composites reinforced with 25% SiC particles in AZ91 alloy are 23%, 47% and 72% higher than those of the matrix alloy.
The density of titanium is 4.5g/cm3, which has the advantages of high specific strength, high temperature strength and corrosion resistance. Due to the high price of titanium, it has been only used in racing cars and some luxury cars. However, there is a lot of experimental research on the application of titanium alloys in automobiles. For example, use α+β It is an engine connecting rod made of titanium alloy. Its strength is equivalent to that of 45 steel, and its weight can be reduced by 30%; β Titanium alloy (ti-13v-11cr-3al, etc.) has a strength of 2000mPa after strong cold processing and aging treatment. It can be used to manufacture suspension springs, valve springs and valves. Compared with high-strength steel with a tensile strength of 2100mpa, the weight of titanium springs can be reduced by 20%.
The biggest resistance to the application of titanium alloy comes from its high price. Toyota Central Research Institute has developed a low-cost titanium matrix composite. The composite material is produced by powder metallurgy with Ti-6Al-4V alloy as matrix and TiB as reinforcement, and has been applied in engine connecting rod.