K. Chawla a high enough temperature or long enough time), diffusion and/or chemical reactions will occur between the components. Two common morphologies of reaction products at an interface in common metal matrix composites are (a)a reaction layer that covers the ceramic reinforcement more or less uniformly, and (b)a discrete precipitate, particle or needle shaped, around the reinforcement. Type(a)reaction is controlled by diffusion of elements in the reaction layer and the square of the reaction zone thickness(r) varies linearly with time(t), i.e. x=Dr where D is the diffusion coefficient. Examples of such a reaction include b/Al and Sic/Ti [8]. An example of such a parabolic growth of the reaction zone in SCS-6 silicon carbide fiber/Ti-45Al-3 V-2Fe-2Mo(wt%)composites at three different temperatures is shown in Fig. 2 [9]. Figure 3 summarizes schematically the effect of time and temperature on the growth of the reaction layer. Silicon carbide fiber reinforced titanium matrix composites are attractive for some aerospace applications. In particular, titanium alloy matrix containing the SCS-6 silicon carbide fiber can have a very complex interfacial chemistry and microstructure Titanium and its alloy are very reactive in the liquid state; therefore, only solid state processing techniques such as diffusion bonding are used to make these composites A schematic of the interface region in these composites is shown in Fig. 4 [10] Type(b)reaction is controlled by nucleation process and discrete precipitation oc curs at the reinforcement/matrix interface. Examples include alumina/magnesium, carbon/aluminum, and alumina-zirconia/aluminum. Figure 5 shows an example,a dark field TEM micrograph, of the reaction zone between alumina fiber and magne sium matrix. Also to be seen in this figure are the deformation twins in the matrix, the result of thermal stresses on cooling during liquid metal infiltration. Aluminum o口△ F1.o[ N 200 Time"(s/2) growth of the reaction zone in SCS-6 silicon carbide fiber/Ti-45AI- 3V-2Fe-2Mo(wt%) composites nt temperatures(adapted from 161)292 a high enough temperature or long enough time), diffusion and/or chemical reactions will occur between the components. Two common morphologies of reaction products at an interface in common metal matrix composites are: (a) a reaction layer that covers the ceramic reinforcement more or less uniformly, and (b) a discrete precipitate, particle or needle shaped, around the reinforcement. Type (a) reaction is controlled by diffusion of elements in the reaction layer and the square of the reaction zone thickness (x) varies linearly with time (t), i.e. x2 = Dt, where D is the diffusion coefficient. Examples of such a reaction include B/Al and SiC/Ti [8]. An example of such a parabolic growth of the reaction zone in SCS-6 silicon carbide fiber/Ti-4.SA1-3V 2Fe-2Mo (wt%) composites at three different temperatures is shown in Fig. 2 [9]. Figure 3 summarizes schematically the effect of time and temperature on the growth of the reaction layer. Silicon carbide fiber reinforced titanium matrix composites are attractive for some aerospace applications. In particular, titanium alloy matrix containing the SCS-6 silicon carbide fiber can have a very complex interfacial chemistry and microstructure. Titanium and its alloy are very reactive in the liquid state; therefore, only solid state processing techniques such as diffusion bonding are used to make these composites. A schematic of the interface region in these composites is shown in Fig. 4 [10]. Type (b) reaction is controlled by nucleation process and discrete precipitation oc￾curs at the reinforcement/matrix interface. Examples include alumina/magnesium, carbon/aluminum, and alumina-zirconia/aluminum. Figure 5 shows an example, a dark field TEM micrograph, of the reaction zone between alumina fiber and magne￾sium matrix. Also to be seen in this figure are the deformation twins in the matrix, the result of thermal stresses on cooling during liquid metal infiltration. Aluminum Figure 2. An example of a parabolic growth of the reaction zone in SCS-6 silicon carbide fiber/ Ti-4.5AI- 3V-2Fe-2Mo (wt%) composites at three different temperatures (adapted from [6])