Interfacial reactions in SCS-6 SiC/Ti-25Al-10Nb-3V-1Mo composites processed by fibre coating with matrix and followed by hot isostatic pressing were investigated with the method of analytical transmission electron microscopy. In as-processed composites, the reaction products are mainly (Ti, Nb)C and (Ti, Nb)5 (Si,Al)3 with small amounts of (Ti, Nb)3 (Si, Al) and (Ti, Nb)3 (Al, Si)C distributed in three layers. In heat treated specimens additional layers of the reaction products were observed. After heat treatment at 700°C for 1000h, the thickness of the reaction zone increases due to the formation and growth of the phases (Ti,Nb)3(Si,Al) and (Ti,Nb)3(Al,Si)C. A heat treatment at 800℃ for 2000h results in a thickening of all the reaction products. The formation and growth of phases in the interface is discussed with respect to the thermal stability of composite properties.

A detailed investigation on the thermally grown oxide (TGO) layers of EB-PVD thermal barrier coatings (TBCs) on as-coated samples and samples that were thermally exposed at 1050°C for up to 1013h was conducted by using transmission electron microscopy (TEM). It was observed that a mixed layer of alumina and zirconia exists in the as-coated condition. The thickness of this mixed layer remained constant over a long period of time. Thickening of the TGO during thermal exposure is due to the growth of a continuous layer of pure α-alumina caused by inward diffusion of oxygen However, a small amount of increase in thickness of the mixed layer was found in the samples exposed at 1050°C for more than 504h, which is predominantly induced by the aggregation of elements Cr, Co, Ni and the formation of spinels in the mixed layer.

MoSi2-matitrix composites reinforced with ZrO2 and SiCparticles were fabricated by means of combustion synthesis (CS) com bined with high-energy mechanical milling (MM) and hot-pressing and sintering. The microstructures and mechanical properties of the composites were investigated by X-ray diffractometry (XRD), scanning and transmission electron microsocopy (SEM and TEM), and with a universal meterials testing machine. The results show that SiC particles are mainly distributed inside the grains of the MoSi2s matrix, while ZrO2 particles are distributed at the inter-granular region and produce coalesence and coarseing of the matrix grains during hot pressing. The room-temperature indentation fracture toughness of the composites reinforced with ZrO2 particles non-stabilzed by Y2O3 (the reinforcing agent is coded as OY-PSZ) was higher than that of the composites reinforced with ZrO2 paticles stabilized by 2.5mol% Y2O3 (the reinforcing agent is coded as 2.5Y-PSZ). However, the latter show higher hend strengths. Moreover, the composites hotpressed at 1400℃has a lower hbend strength than hot-presses monolithic MoSi2. It is obvious that there is a synergistic effect of SiC and ZrO2 on the mechanical properties of ZrO2/(MoSi2+SiC) composites.