Some Aspects of Processing and Properties of Composite Material with Si-C Particles
D. Nedelcu a, I. Carcea b, L. Tabacaru a and C. Ciofu a
aFaculty of Machine Manufacturing and Industrial Management;
bFaculty of Science and Materials Engineering "Gheorghe Asachi", Technical University of Iasi, 700050 Iasi, Romania
Full Text PDF
The processing of composite materials with metal matrix reinforced with carbon particles, graphite or SiC (Silicon Carbide) is decisively determined by the transfer of the reinforcing particles from the gaseous atmosphere into the molten metal and then by their transfer from liquid into solid. The degree of incorporation, the uniformity of particle distribution and finally all the properties of the composite materials depend on the way in which the transfer conditions from one phase to another have been accomplished. According to the thermodynamic principles, the transfer of the reinforcing particles from one phase to another can happen without external energy input only if the variation of the total free enthalpy is negative. The estimation of the direction of transfer can be done after the determination of critical measurements to the balance of forces that act on the reinforcing element. The particles wetted by the liquid metal and with density of its nearest will be integrated in the melt without external energy input, and those dry and light need additional energy consumption (powder injection, melt stirring etc.). The stalling speed of the SiC particles to the gas/liquid interface is influenced by the density difference and the reinforcing particles size. The critical moving speed of the solidification front is decisively influenced by the difference between σPS and σPS, inter-phase tensions, as well as by the reinforcing particles size, if their density significantly differs from the one of the liquid alloy. Compared with the initially used alloy, the pull strength is doubled for some samples of obtained composite material. The ultrasonic testing disclosed the presence of some very small spots (porosities) which don't have a major influence on the tensile specimens subjected to pulling. From this reason, a very clear display of the bottom echo can be observed, which justifies the uniformity of the casting process. At the level of the matrix, the presence of the carbon to the separation limit between matrix and reinforcement can be observed, which confirms that during the processing Aluminium Carbide Al4C3 has been formed. The presence of these carbides considerably improves the wetting process.
DOI: 10.12693/APhysPolA.120.344
PACS numbers: 81.05.Mh, 81.05.Ni, 81.05.Pj, 81.05.Qk, 12.60.Rc