CHARACTERIZATION OF CO- CONTINUOUS-COMPOSITES BY DIFFERENTIAL THERMAL ANALYSIS AND DILATOMETRY

摘要

Metal and ceramic matrix composites arepromising materials for applications in the transport field.However; to this purpose, significant cost reductions arenecessary through the development of new processingtechniques. In-situ fabrication processes, which are suitable forthe production of near-net-shape components, can significantlyreduce the cost by minimizing or eliminating costly post-firemachining. Among these processes, directed metal oxidation [1-3], reaction bonded alumina [4] and reactive metal penetration[5-9] have been recently investigated. In the present study,composites produced by reactive metal penetration (RPM) wereinvestigated. The RPM method, first developed by M.C. Breslinat Ohio State University [7-9], involves the submersion of asilica preform in molten aluminum, held at a temperature above1000 deg C, whence the following reaction occurs:3SiO_2 +4Al->Al_2O_3+3Si[Al]Due to the superior thermodynamic stability of alumina withrespect to silica, the final material consists of a continuousnetwork of alumina (about 70 percent), which provides highstiff ness and wear resistance, interpenetrated with acontinuous network of aluminum, which improves bothtoughness and thermal conductivity. Because of thesecharacteristics and high specific strength, these co-continuous-ceramic-composites (C~4) may find applicationsin the aerospace and auto-motive fields [10,11].The objective of the research reported here was to investigatethe behavior of two C~4 materials (Al_2O_3-Al5Cu2Si andSiC- Al_2O_3-Al20Si) during thermal exposure and thermal cycling.