unetched regions around the fiber are niobium rich the dark etching phase in the matrix is beta phase or transformed beta phase and the light regions in the matrix are alpha 2 a fiber of the plate of example 1 and its surrounding niobium coating are seen in greater detail in fig2 examination of the sample showed that there was a niobium rich region surrounding or partially surrounding the fibers of fig1 there was essentially no continuous alpha 2 envelope no cracks were seen in the niobium rich regions of beta phase or ordered beta phase adjacent to the fibers in this sample in the discontinuous alpha 2 regions in contact with the fibers a few instances of cracking were observed the reaction zone between the fibers and the plasma sprayed niobium was about 1 u03bcm thick in a composite made without the plasma sprayed niobium coating on the fibers as for instance in examples 6 8 the reaction zone between fiber and matrix was about 2 5 u03bcm thick since increasing the reaction zone thickness can have a deleterious effect on mechanical properties limiting the reaction zone thickness by deposition of a niobium coating and by process control can be important to preserving the mechanical properties tensile samples were made from the composite formed with the aid of the niobium coated fibers as well as from composites made without niobium coated fibers tests of these tensile samples were made at room temperature with the applied stress perpendicular to the fiber axis the data obtained from this testing are listed in table i table i______________________________________room temperature.