| Al foams can be applied in a wide range of areas because of their excellent properties. Al foams prepared by powder compact melting (PCM) technique have many characteristics and advantages. Al alloy, as matrix materials, not only will improve the properties of Al foams but also make the preparation technology be easily controlled as the melting point of Al alloy is lowered, which widers the application areas.Based on PCM and with the combination of real-time image pickup and cross section processing, the paper studies the effects of sample temperature, presetting furnace temperature (heating rate) and size of steel tube on foaming property of Al-Si alloy foams. As a result, the interrelation between process parameters (presetting furnace temperature and sample temperature), foaming behavior of Al alloy foams and pore structure has been obtained. And Al-Si alloy foams and Al-Cu alloy foams have been produced. The sample of compression property has been directly produced by a self-made mould. Test of and analysis into the static compression property of Al alloy foams with different materials and porosities as well as different heat treatment have also been carried out. These results lay a foundation for the further research into and application of big-size Al foams. The results show that:(1) Sample temperature and presetting furnace temperature mainly affect the foaming and pore structure of Al foams. The higher the furnace temperature, the larger the heating rate and the shorter the foaming time.In the experiment, when the presetting temperature ranges from 690℃to 750℃, sample will be full of the steel tube. When the sample temperature is between 670℃and 720℃, Al-Si alloy foams are provided with porosity of 77%-82%, the equivalent diameter of gas pore between 1.3mm and 2.1mm and pore circularity of 0.67-0.84. The foaming evolution of Al alloy foams includes the nucleation, growth, merging and cracking of pores, and the pore morphology is small sphere, big sphere and polygonization.(2) Stress-strain curves of three different materials each consist of three stages, elastic region, yield region, densification region, which are of great difference. The stress-strain curves of pure Al foam manifests apparent yield region and the absence of rise and fall, which is typical of plasticity compression. The stress-strain curves of foamed AlSi7 shows slight fluctuation in yield region. The stress-strain curves of foamed AlSi7Cu4 begin a considerable stress fluctuation along with porosity, which shows to some extent fragility. When they are provided with the same porosity, foamed AlSi7Cu4 boasts the largest compression strength, foamed AlSi7 comes second and foamed pure Al is the third. When they are under experimenting condition and the porosity ranges between 68% and 76%, the compression strength of foamed AlSi7Cu4 is 15-30MPa, foamed AlSi7 10-20MPa and foamed pure Al 5-10MPa.(3) Porosity has a considerable effect on compression property of Al foams. Stress-strain curves move up with the decrease of porosity, while modulus of elasticity, compression strength and energy absorption capability increase correspondingly.(4) Heat treatment has little influence on the shape of stress-strain curves of static compression property of Al alloy foams, but the curve goes upward, compression strength is enhanced. After foamed ZL107 with porosity between 68.1% and 76.0% undergo T5 heat treatment, its compression strength will increase by between 10% and 30%. The effects of heat treatment are more prominent when porosity is in a low level. |
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