Squeeze casting of SiC p /Al-alloy composites with various contents of reinforcements
- PDF / 1,519,910 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 44 Downloads / 163 Views
Aluminum matrix composites reinforced with various contents and sizes of silicon carbide particles (SiCp) were fabricated by squeeze casting. A lower melting point AA A383 aluminum alloy (A383 Al) was squeezed into the higher melting point SiCp/pure aluminum (SiCp/pure Al) and SiCp/AA 6061 aluminum alloy (SiCp/6061 Al) preforms. The volume percents of the ceramic reinforcements were effectively lowered from traditional 50 to 8â25 vol% by the addition of pure Al and 6061 Al powders in the preforms. The SiC particles uniformly distributed within the matrices, and no pore was found in these composites. The growth of silicon precipitates in A383 Al alloys was limited by the addition of the aluminum alloy powders and SiC particles, and the tensile properties of the alloys were effectively enhanced by the refinement of the silicon precipitates. The tensile strengths and elongations of the SiCp/pure Al/A383 Al and SiCp/6061 Al/A383 Al composites were both better than those of the A383 Al alloy. The T6-treated 12-âŪm SiCp/6061 Al/A383 Al composite exhibited the highest tensile strength of 301 MPa.
I. INTRODUCTION
Metal matrix composites (MMCs) have been developed and applied as structural materials in aerospace and automobile industry for two decades because of their high specific strength, high specific stiffness, good elevated-temperature properties, and better wear resistance.1â5 Among these composites, short fiber and particulate-reinforced aluminum matrix composites attract a lot of emphases because of their isotropic properties. Methods for the production of particulate-reinforced MMCs mainly include liquid casting,6,7 and powder metallurgy.8 Though traditional liquid casting offers an advantage of high economic profit, many defects, such as gas porosity, oxide inclusions, clustering of the reinforcements, and intensive interfacial reactions between the reinforcements and the molten metal, incorporate with these products and result in worse properties.9 On the other hand, the powder metallurgy method offers good properties; however, production cost is expensive. Squeeze casting10â13 eliminates gas porosity and reduces interfacial reactions that occur in traditional liquid casting by large pressures and rapid solidification rates, respectively, offering a combination of high economic profit and good properties. Before squeeze casting, the preforms need to be prepared by mixing the reinforcements and binders homogeneously. Molten metals are then squeezed into the preforms by a large pressure. The application of high pressure during squeeze casting is 376
J. Mater. Res., Vol. 17, No. 2, Feb 2002
required not only to enhance the wettability of the molten metals to the reinforcements but also to drive the molten metals into the space in the preforms and obtain poreless bulks. Besides, it makes the molten metals closely contact the mold, enhancing heat dissipation and rapid solidification of the molten metals. Rapid solidification rates construct fine microstructures and offer good mechanical properties of the composite
Data Loading...
