Abstract
Fiber reinforced metal composites were fabricated by diffusion welding. The matrices used were commercially pure titanium (CPTi) and two kinds of titanium alloys (Ti-6Al-4V and Ti-21V-4Al), and the filaments were two kinds of SiC-CVD fiber. The structure and the distribution of elements in reaction zone between matrix and filament both in as-fabricated state and in heat-treated state were investigated by microscopy, SEM/EDX microanalyses and transmission electron microscopy (TEM). From the results obtained, the kinetics and mechanism of growth of the reaction zone were discussed.
It was found that the reaction zone was composed of TiC and Ti5Si3 and the growth rate of the zone in Ti-21V-4Al alloy matrix was lower than those in CPTi and Ti-6Al-4V alloy matrices.
The apparent activation energy for the growth of the reaction zone, derived from the relation between heating temperature and reaction rate constants, revealed that the value of the activation energy was different between the heating temperatures above and below the α-β transformation (1153K) in case of CPTi or β transus temperature (1268K) in case of Ti-6Al-4V alloy matrices because of rapid diffusion rate and low solubility of carbon in beta phase.
In the composite of the Ti-21V-4Al alloy matrix, the growth rate of raection zone was very low compared with that in the Ti-6Al-4V alloy, suggesting that large amounts of alloying elements of V and Al reduced the growth rate of reaction zone. This result indicates that the Ti-21V-4Al alloy is suited to the matrix of composites reinforced with SiC filament.
