| Particles reinforced aluminum matrix composite material because of its having a high weight, high specific strength and specific stiffness, good thermal stability, good wear resistance, low thermal expansion coefficient and high heat resistance, are widely used in aerospace, energy, machine tools, advanced weapons and automobile. Currently the process of particle reinforced aluminum matrix composites are roughly classified into two types, one is Mandatory addition method the other is the in situ reaction. Compared to the mandatory addition method, the reinforcing particles prepared by in-situ reaction and have small particles, heat stability and well bonded to the substrate. As the same time, mechanical stirringultrasonic vibrations can effective grain refining, uniform organization greatly enhances the mechanical properties of the in situ composites. Therefore, in recent years, mechanical casting-ultrasonic vibration assisted in situ reaction to prepared particle reinforced aluminum matrix composites having attention.The AlFeSi/Al in-situ composites was prepared by mechanical casting and ultrasonic vibration combined with in-situ reaction technique by changing process parameters(Fe content, stirring-ultrasound temperature, stirring-ultrasonic time). The Microstructure, phase components and mechanical properties(Vickers hardness, wear resistance, compression performance, bending properties) was investigated by X-ray diffraction(XRD), scanning electron microcopy(SEM), energy dispersive spectroscopy(EDS), optical microscope, XHV-1000 digital micro hardness tester, MFT-4000 surface properties of multifunctional materials tester, electronic universal testing machine and M2000 wear tester. The results show that:(1) The size, shape and distribution of reinforcing phase particles in AlFeSi/Al in-situ composites was related to Fe content, stirring temperature and stirirring vibration time. With the increase of Fe content, the long needle-like β-Al5 FeSi gradually grew into a plate by a long needle into the lump grew last in in-situ composites. And the reinforcing phase particles distribution more uniform because of stirring. When the ultrasonic vibration temperature was 750℃, the shape, size and distribution of reinforcing phase particles was the best, and the numbers are the most. However, when the stirring temperature higher than 750℃, there is no impact on shape, size and distribution. When the ultrasonic vibration time was 8min, the shape, size and distribution of reinforcing phase particles was the best, and the numbers are the most. At this time, the reinforcement is beneficial to in-situ composites.(2) The reinforcement of AlFeSi has an obvious enhancement effect of in-situ composites, when the mass fraction of Fe was 6%, the stirring temperature was 750℃, the stirring time was 8min is the best. The hardness of composites has a peak value(111.5), which is 1.5 times that of Al-Si alloy, The wear resistance is the best(wear rate is 0.231%), which is 7.4 times that of Al-Si alloy. the wear mechanism is mainly abrasive wear. the compressive strength and the bending strength has a peak value(548.2MPa which is 5.4 times that of Al-Si alloy and 369 MPa which is 3.5 times that of Al-Si alloy).(3) To compared with microstructure and mechanical properties of in-situ composites,which prepared by two casting process. The ultrasonic vibration is the best.(4) It is caused acoustic cavitation, acoustic streaming, and thermal effects when ultrasonic vibration propagation in melt. The generation of these effects is beneficial to size, morphology, and distribution of AlFeSi intermetallic compounds. Effect of acoustic cavitation bubble crash instantly are able to generate 103-104 K high temperature and high pressure up to 105 MPa, it is greatly improved the mechanics properties of AlFeSi/Al in-situ composites... |
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