Scanning and transmission electron microscopy study of the microstructural changes occurring in aluminium matrix composites reinforced with SiC particles during casting and welding: interface reactions

Abstract

Processing of aluminium matrix composites (AMCs), especially those constituted by a reactive system such as Al-SiC, presents great difficulties which limit their potential applications. The interface reactivity between SiC and molten Al generates an aluminium carbide which degrades the composite properties. Scanning and transmission electron microscopes equipped with energy-dispersive X-ray spectroscopes are essential tools for determining the structure and chemistry of the Al-SiC interfaces in AMCs and changes occurring during casting and arc welding. In the present work, an aluminium-copper alloy (AA2014) reinforced with three different percentages of SiC particles was subjected to controlled remelting tests, at temperatures in the range 750-900 degrees C for 10 and 30 min. Arc welding tests using a tungsten intert gas with power inputs in the range 850-2000 W were also carried out. The results of these studies showed that during remelting there is preferential SiC particle consumption with formation of Al4C3 by interface reaction between the solid SiC particle and the molten aluminium matrix. The formation of Al4C3 by the same mechanism has also been detected in molten pools of arc welded composites. However, in this case there was formation of an almost continuous layer of Al4C3, which protects the particle against further consumption, and formation of aciculate aluminium carbide on the top weld. Both are formed by fusion and dissolution of the SiC in molten aluminium followed by reaction and precipitation of the Al4C3 during cooling.

Active coatings for SiC particles to reduce the degradation by liquid aluminium during processing of aluminium matrix composites: study of interfacial reactions

“…7), which underwent rapid degradation in contact with environmental humidity, forming hydrated Al–O products. The mechanisms of formation and degradation of these reaction products were the same as those explained by Ureña et al . (1999), during remelting of an AA2014 matrix composite reinforced with 13% in volume of SiC particles.…”

“…Reactivity between molten aluminium and SiC particles in composites and the detrimental effects of this, such as reducing reinforcement and interfacial strengths and increasing corrosion susceptibility, have been studied in depth by several authors (Warren & Anderson, 1984; Laurent et al ., 1987). Here, we focus our studies on electron microscopical analysis of the mechanisms of interface reaction during casting and welding in both SiC particle (Ureña et al ., 1999) and whisker (Ureña et al . 2001a, b) reinforced aluminium composites.…”

Graphyne and Graphdiyne: Versatile Catalysts for Dehydrogenation of Light Metal Complex Hydrides

“…Table 3 also shows that two Al−C bonds with lengths of 0.204 and 0.215 nm are formed for NaAlH 2 on GD and four Al−C bonds, all with bond lengths of 0.208 nm, are formed for NaAlH with GD, which agrees with the experimental measurements of 0.190−0.222 nm. 18 In this regard, the catalytic effect of GD on the complex metal hydride is stronger than that of GP.…”

Compressive properties of Al-A206/SiC and Mg-AZ91/SiC syntactic foams

“…Coarse phases containing Fe and Si were also observed to be dispersed in the Aluminum alloy specimens. The formation of these intermetallics may be as a result of the presence of excess Si in the matrix due to the partial reaction of the SiC spheres to form aluminum carbides [44], as well as partial dissolution of the steel tube that was used as a crucible. Some cracking of the spheres is also observed in these micrographs, which likely occurred during or after solidification due to CTE mismatch as there is little to no infiltration of the spheres.…”