先进复合材料及其制备讲义.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * * Summary of Ultrasonic Processing High-intensity ultrasonicwaves are capable of distributing and dispersing nanoparticles in Mg matrix with non-linear effects in liquids, especially transient cavitation. From the high-resolution SEM observation, SiC nanoparticles are almost uniformly distributed in the matrix, although some small clusters (less than 300 nm) still exist in matrix. EDS analysis indicates that the SiC nanoparticels are partly oxidized. Compared to pure cast AZ91D, cast AZ91D/5SiC yields Mg2Si compounds. The Mg2Si compound in the composites might be resulted from chemical reactions taking place during the ultrasonic processing of composites. Si could be introduced into the magnesium matrix by reactions between Mg and the SiO2 layer that covers the surfaces of SiC nanoparticles. The XPS analysis also indicates the existence of SiO2. The microhardness of nanoparticle reinforced magnesium composites improved with the increasing fraction of SiC nanoparticles. The microharness of AZ91D/5SiC increasedby 75% compared to that of AZ91D. Magnesium Matrix Nano-composite Fabrication – Case 4 J. Lan et al.：Materials Science and Engineering A386 (2004) 284–290 Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd. The interaction between high-intensity ultrasonic waves and nano-sized particle clusters in magnesium melts High-intensity ultrasonic waves are especially useful in that they generate some important non-linear effects in liquids,namely transient cavitation and acoustic streaming, which are mostly responsible for benefits including refining microstructures, degassing of liquid metals for reduced porosity, and dispersive effects for homogenizing. Magnesium Matrix Nano-composite Fabrication – Case 4 Evaluation only. Created with