The Role of Ni-P Coating Structure on Fly Ash Cenospheres in the Formation of Magnesium Matrix Composites
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METAL matrix composites reinforced with different fibers or ceramic particles deserve special consideration due to their properties, especially low density, high specific stiffness and strength, high damping capacity, and good dimension stability.[1–3] What is more, metal matrix composites based on different matrix alloys with fly ash cenospheres are materials that have recently been intensively investigated.[4–6] Cenospheres (also called microballoons) are thin-walled, hollow, ceramic particles of different sizes (up to 500 lm) and a very low true density equal to about 0.4 to 0.6 g/cm3. The cenosphere walls belong to glass ceramic materials based on aluminosilicate glass, mullite, quartz, calcite, iron oxides, and calcium silicates and sulfates.[7–9] The wall thickness of cenospheres is generally 5 to 10 pct of that of their diameter, whereas the glassy phase content in the wall material is about 80 to 90 pct. Hollow cenospheres are filled with gases like CO2 and N2 with traces of CO, O2, and H2O. It should also be noted that cenospheres as a by-product of coal-fired power plants
KATARZYNA N. BRASZCZYN´SKA-MALIK and JACEK KAMIENIAK are with the Institute of Materials Engineering, Czestochowa University of Technology, Al. Armii Krajowej 19, 42200 Czestochowa, Poland. Contact e-mail: [email protected] Manuscript submitted November 21, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS A
could contribute to reducing the cost of metal matrix composites.[10,11] In recent years metal matrix composites based on magnesium alloys with cenospheres have also been synthesized.[12–15] Magnesium alloys are light metallic structural materials and have a unique combination of properties, which are very attractive in such applications as the automotive, aerospace, and electronic industries.[15–17] Therefore, these alloys are attractive as a composite matrix. Rohatgi et al.[18] obtained by the die casting technique a composite based on the AZ91 magnesium alloy matrix with cenospheres. Analogical material was fabricated by the stir casting method by Huang et al.,[19] Lu et al.,[20] and Gupta et al.[21] A composite based on the AZ91 alloy with cenospheres was obtained by the pressure infiltration process by Liu et al.[22] Daoud et al.[23] investigated a composite fabricated on the base of the ZC63 magnesium alloy by the stir casting technique. The main problem during the fabrication of cast metal matrix composites with cenospheres is the destruction of their walls due to mechanical damage or chemical reaction with the liquid alloy matrix.[1–4,12] During the processes of composite fabrication like stir casting, die casting, or pressure infiltration method, thin-walled, hollow cenospheres could easily undergo damage due to mixing or pressure actions. On the other hand, magnesium alloys (due to their high reactivity) are especially prone to reactions with the oxides forming the cenosphere walls. In consequence, the obtained composites are characterized
by a majority or part the cenospheres broken and filled by the matrix alloy. The main re
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