Tensile properties and strengthening mechanisms of SiC p -reinforced aluminum matrix composites as a function of relativ
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Jingpei Xiea) College of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023, China (Received 28 February 2013; accepted 24 June 2013)
Metal matrix composites manufactured by the powder metallurgy route often exhibit different tensile strength due to particle geometrical reasons. The tensile strength tendency was studied in 2024 Al/30% SiCp composites as a function of relative particle size (RPS) ratio between the matrix and reinforcement particles. Dry blended composite powders, with different RPS ratios, were hot-pressed in vacuum, their microstructures were observed, and their tensile properties were measured. It was found that a decrease in RPS ratio resulted in a decrease in tensile strength, as a result of improved distribution of the SiCp. Despite their low density and heterogeneous distribution, 3-lm SiCp-reinforced composites had maximum tensile strength. The main reasons were due to the few fracture for small SiCp and the strengthening of the matrix microstructure from small particle effects. Solution treatment plus aging of the composites with the RPS ratio of 10:3 resulted in a significant improvement (42%) in strength due to the smaller diffusion path length for the alloying element.
I. INTRODUCTION
The attractive physical and mechanical properties that can be obtained with metal matrix composites (MMCs) such as high specific modulus, strength, and thermal stability have been documented extensively.1–4 The MMCs have higher strength in shear and compression and higher temperature capability because they are a combination of metallic properties (ductility and toughness) and ceramic properties (high strength and modulus). Interest in MMCs for aerospace, automobiles, and other structural applications has grown over the last few years.5,6 In composites produced by the powder metallurgy (PM) technique, the spatial distribution of the reinforcements is much more uniform although clustering still occurs on a smaller scale and especially in the case of finer reinforcements. In PM composites, clustering can occur either because of static charges present on reinforcement particle surfaces7 or due to geometrical reasons when there is a difference between the particle sizes of the matrix and reinforcement.8 This can be controlled by optimizing the relative particle size (RPS) ratio, which can be defined as the ratio between the average size of the matrix particles and a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2013.202 J. Mater. Res., Vol. 28, No. 15, Aug 14, 2013
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that of the reinforcement particles. RPS ratio optimization may lead to an improvement in the uniformity of reinforcement distribution in MMCs and in turn improve the mechanical properties.9,10 RPS ratio can be varied by changing the particle size of either the reinforcement or the matrix, separately or simultaneously. While the mechanical properties are very much dependent not only on the RPS ratio but also on
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