Apply Impregnation Technology to Produce Aluminum Alloy Composites

[China Aluminum Network] In the automotive industry, there are many parts for casting aluminum alloys, such as engine blocks, pistons, cylinder heads, water pumps, joints in cooling systems, petrol pumps in combustion systems, nozzles, and transmission systems. Transmission and so on. For such aluminum alloy castings, if there is oil leakage, it will seriously affect the performance of the vehicle. For this reason, it is more effective to use impregnation technology to treat it, and it can save resources and save energy, and it is also conducive to environmental protection.

As we all know, metal parts in the casting process, because of its solidification shrinkage and shrink holes, which inevitably caused by hydrogen, nitrogen and other gases pore defects. In addition, the metal sintered body and the ceramic sintered body manufactured by the powder metallurgy method without using the casting method are themselves porous bodies. In order to increase their mechanical properties, it is necessary to eliminate and reduce their internal porosity defects. Therefore, the purpose of research and development of impregnation technology is here.

At present, according to relevant data records, there are three main methods for impregnation:

Internal pressure impregnation;

Vacuum before impregnation;

After impregnation vacuum vacuum method.

If the inside of the impregnated object is porous, it must be replaced with an immersion liquid. While under vacuum or decompression, the immersion liquid can easily replace the air. On the other hand, even when the wettability between the impregnating liquid and the impregnated material is poor and the impregnation speed becomes high, high hydraulic pressure can be effectively generated by the pressure-increasing pump, and the impregnated material can be heated by vacuum pressurization. Increase the fluidity of the impregnating fluid so that a good impregnation process can be performed with a uniform temperature distribution.

The pressure impregnation method has many advantages, but it is also technically difficult to perform a vacuum-high temperature treatment, and there are many legal restrictions on the use of pressure vessels. The high temperature vacuum pressure impregnation apparatus shown in FIG. 1 overcomes the above problems. As in the previous step 1 (heating and pressurizing treatment), the pressurization is performed while heating, the number of gas molecules in the tank increases, the convection conduction efficiency increases, and the temperature distribution of the impregnating liquid and the impregnated material becomes uniform. In the previous step 2 (vacuum treatment), impurities such as air, moisture, and organic gas in the impregnated material can be excluded. After vacuum treatment, the permeability of the impregnating liquid is increased.

In the immersing step 1 (immersion treatment), for example, the impregnated material is placed in the immersion liquid by an elevating machine, and the immersion liquid penetrates inside the impregnated product. In the immersing step 2 (pressurized immersion treatment), the immersion liquid can permeate the inside of the impregnated product. If a high viscosity immersion liquid is used, a sufficient penetration effect can be produced even if the vacuum treatment is insufficient. At the same time, bubbles due to the pressurization can also be suppressed. The impregnated material is lifted by the processing step (cooling+exhaust treatment) and cooled to harden the impregnating liquid. Subsequently, the impregnated substance is returned to the atmosphere under reduced pressure, and at this time, bubbles are also expanded in the hardened impregnation liquid.

In order to apply the impregnation technique to the manufacture of pistons for automobile engines, the pressure is controlled as far as possible within a certain range during impregnation so as to avoid the use of high pressure vessels and to improve the gravity casting device. At the same time, low pressure impregnation methods below 0.8 MPa have also been developed.

2 Aluminum alloy composite materials produced by low-temperature impregnation method are used as aluminum alloy composite materials for automobile engine pistons and other components, and the weight must be light and the temperature must be high. Originally such parts were produced by high pressure casting and powder metallurgy. However, these two methods are difficult to produce large-scale and complex-shaped components. In order to avoid these disadvantages, we have adopted metal composites made of metal fibers as reinforcing materials and low-pressure impregnation to produce large-sized and complex-shaped metal composite parts. It has been verified by experiments that the low-pressure impregnation method is suitable for manufacturing aluminum alloy composite materials, and can obtain a void-free composite material with solidification shrinkage defects and poor flowability.

A3360 (Al, 13% Si, 1.5% Ni, 1.3% Cu, 1.3% Mg) in the ASTM standard was used as the base alloy. The iron-chrome-silicon (Fe, 20% Cr, 5% Si) fiber produced by Japan Spring Co., Ltd. was selected as a reinforcing material. This metal fiber and aluminum alloy had good wettability, and it was produced by the melt extraction method. Fine crystal grains therefore have high strength properties. Specifically, it has a tensile strength of 950 MPa and 650 MPa at room temperature and 673 K, respectively, and its elongation rates are 15% and 30%, respectively.