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论文类型：期刊论文

发表时间：2015-02-11

发表刊物：MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

收录刊物：SCIE、EI

卷号：625

页面范围：357-368

ISSN号：0921-5093

关键字：TiB2 particles; In situ composites; Stirring; Tomography; Microstructure; Mechanical properties

摘要：In this study, a new technique involving mechanical stirring at the salts/aluminum interface was developed to fabricate TiB2 particulate reinforced aluminum based in situ composites with improved particle distribution. Processing parameters in terms of stirring intensity, stirring duration and stirring start time were optimized according to the microstructure and mechanical properties evaluation. The results show that, the first and last 15 min of the entire 60 min holding are of prime importance to the particle distribution of the final composites. When applying 180 rpm (revolutions per minute) stirring at the salts/aluminum interface in these two intervals, a more uniform microstructure can be achieved and the Al-4 wt% TiB2 composite thus produced exhibits superior mechanical performance. Synchrotron radiation X-ray computed tomography (SR-CT) was used to give a full-scale imaging of the particle distribution. From the SR-CT results, the in situ Al-xTiB(2) composites (x=1, 4 and 7, all in wt%) fabricated by the present technique are characterized by fine and clean TiB2 particles distributed uniformly throughout the Al matrix. These composites not only have higher yield strength (sigma(0.2)) and ultimate tensile strength (UTS), but also exhibit superior ductility, with respect to the Al-TiB2 composites fabricated by the conventional process. The sigma(0.2) and UTS of the Al-xTiB(2) composite in the present work, are 260% and 180% higher than those of the matrix. A combined mechanism was also presented to interpret the improvements in yield strength of the composites as influenced by their microstructures and processing history. The predicted values are in good agreement with the experimental results, strongly supporting the strengthening mechanism we proposed. Fractography reveals that the composites thus fabricated, follow ductile fracture mechanism in spite of the presence of stiff reinforcements. (C) 2014 Elsevier B.V. All rights reserved.