Abstract
The paper details the studies carried out on a dual-size particulate composite prepared by stir casting using A 356 aluminum alloy and B4C powders. Three composite compositions, viz., A356 plus 2% B4C (44µm size and 105µm size in 1:1 ratio), 4% B4C (3:1 ratio), and 6% B4C (1:3 ratio) were cast in finger molds, from which test specimens were prepared for hardness and tensile tests as well as for metallography. Vickers hardness tests, tensile tests and microstructure analysis using an optical microscope were conducted. The results obtained indicated that the B4C particles were evenly distributed in the alloy matrix. EDS also revealed the presence of B4C in all the three composites. In general, the hardness and tensile strengths increased with increase in concentration B4C powders. While the increase in hardness was increases less than 15%, there was significant increase (more than 35 %) in tensile strength. However, the ductility represented by % elongation, which was already very low in A 356 cast alloy (24.2%,), further decreased in composites. Tensile fractography results shows inter crystalline fracture where the breakage in the B4C particle instead of deboning were observed.
Highlights
Aluminum alloys find application in diverse fields owing to their high strength-to-weight ratio, low cost, and ease of fabrication [1,2,3]
The common reinforcement particles used in AMMCs are graphite, SiO2, SiC, Al2O3 and B4C used in small percentages of about 2 to 8% [8,9,10,11,12]
TMicrostructure he photomicrographs of the as-cast structures of base A 356 alloy, and AMMCs with A 356 and 2% B4C, 4% B4C, and 6% B4C respectively is shown in the Fig.5.(a to d), From Fig. 5(a), it is seen that the cast structure of the base A 356 alloy is dendritic or semi-dendritic
Summary
Aluminum alloys find application in diverse fields owing to their high strength-to-weight ratio, low cost, and ease of fabrication [1,2,3]. Substituting the base aluminum alloys with particulate composites has the advantage of improving the mechanical strength parameters without seriously disturbing the thermal and electrical conductivities and other properties. An AMMC with B4C particles may be expected to have higher strengths than other AMMCs. The work presented here, which is part of a larger comprehensive study, is based on aluminum alloy particulate composites with B4C particles. Two sizes of B4C particles (44 μm, and 105 μm) in different ratios were employed to obtain three AMMCs in the as-cast condition. These were evaluated for their microstructural features and mechanical properties using standard testing procedures
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