Amorphous NiTi films deposited by magnetron sputtering have been studied. The results show that it is easier for precipitation to occur in crystallized films and that, in the films aged at 550℃ for 1h, the parent phase transforms to rhombohedral phase at 27℃ and then to martensitic phase at 2℃.

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.

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.

In the course of preparation of titanium matrix composite by fiber-coating method, it is one of the important procedures to deposit titanium alloy onto SiC fiber. In our experiment, SiC fiber was coated with Ti-6Al-4V by magnetron sputtering. And then the coating was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS). The coating whose composition is consistent with the target material, and whose thickness is uniform, has (001) texture preferred orientation. In addition, deposition rate, dimension of crystallites and surficial morphology are changed with sputtering parameters.

Interfacial processes in SCS-6 SiC/TiB2/Super a2 composites were investigated by means of analytical transmission electron microscopy (TEM). No reaction between the TiB2 coating and the carbon coating of the fibres can be found in the as-processed specimen. At the TiB2/matrix interface the TiB2 transforms into both a homogeneous layer and needles of TiB which are distributed in the matrix. This process takes place according to the reaction TiB2+Ti=2TiB. The TiB2 coating is consumed completely in the specimen heat treated at 9008C for 64h. At this time TiC and Ti3AlC form at the TiB/C-coating and the TiB/matrix interface, respectively. Prolonging the holding time at 9008C, reaction layers thicken continuously following parabolic reaction kinetics. The paper additionally discusses the formation mechanisms of the reaction products.

The interfacial reaction zone of SCS-6 SiC/Ti2AlNb composites consists of two TiC layers with fine and large grains,respectively, and a layer of Ti3Si separating the large grained TiC layer with matrix. A discontinuous layer of Ti5Si3 was identified between the two TiC layers. Some Ti3AlC particles distribute within the Ti2AlNb matrix in thermally exposed composites. The formation mechanism of the reaction products was discussed.

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.

Interfacial reactions in SCS-6 SiC/Ti-25A1-10Nb-3V-1Mo composites processed by fibre coadng with matrix material, hot isostatic pressing and thermal~eadng for simulation of service conditions were studied by analytical transmission electron microscopy. In the as-processed specimen three reaction layers were observed. Adjacent to C coating of the SCS-6 fibre no mixture of TiC and Ti5Si3 was found reported in literature [Rhodes, C. G., Mat. Res. Soc. Symp. Proc., 1992, 273, 17; Baumann, S.F., Brindley, P.K. and Smith, S.D., Metall. Trans., 1990, 21A, 1559; Smith, P.R., Rhodes, C.G. and Revelos, W.C., in Interfaces in Metal-Ceramics Composites, eds R.Y. Lin, R.J. Arsenault, G.P. Martins and S.G. Fishman, TMS Press, New York, 1989, PP. 35-58; Badini, C., Terraris, M. and Marchetti, F., J. Mater. Sci., 1994, 2]. Instead, two sublayers were determined. Sublayer l close to C coating was identified as (Ti, V)C and sublayer 2 as (Ti, V, Nb)5 Si3. The second layer is composed of larger equiaxed grains of (Ti, Nb) C and separated from matrix by a third layer of (Ti, Nb)5 (Si, A1)3. Small amounts of (Ti, Nb)3 (Si, A1) and (Ti, Nb)3 (Al, Si) C were also identified. In the specimens heat treated at 700℃ and 800°for up to 3000h, three, four or five reaction layers were found. In all specimens the reaction products of the first two layers are the same. The additional layers consist of the (Ti, Nb)3 (A1, Si)C, the (Ti，Nb)3 (Si, A1) or the (Ti, Nb)5 (Si, AI)3 phase. These phases are arranged in different sequences. At the treatment temperature of 700℃ the thickening of the interfacial reaction zone is mainly due to the growth of (Ti, Nb)3 (A1, si)C and (Ti, Nb)3 (Si, A1). The growth of these phases is probably responsible for the slow decrease of mechanical properties of the composites during heat treatment. A kinetic analysis indicates that the growth of the reaction zone is a diffusion controlled process. The activation energy was determined to be 368 kJ/mol for the total reaction zone, 302kJ/mol for (Ti, Nb)3 (A1, Si)C and 18l kJ/mol for (Ti, Nb)3 (Si, A1) phase. The experimental results and a crystallographic analysis indicate that (Ti, Nb)3 (Si, A1) is not a diffusion barrier for the carbon and titanium diffusion.