Pd. Nicolaou et al., AN EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THE RAPID CONSOLIDATION OF CONTINUOUSLY REINFORCED, METAL-MATRIX COMPOSITES, Metallurgical and materials transactions. A, Physical metallurgy andmaterials science, 27(6), 1996, pp. 1719-1730
The feasibility of the rapid consolidation of T-14Al-21Nb/SCS-6 foil/f
iber/foil composites using a forging approach was established as an al
ternative to slower and more expensive processes such as those based o
n hot isostatic pressing (HIP) or vacuum hot pressing (VHP). A firm ba
sis for the technique was developed through theoretical analyses of te
mperature transients, forging pressures, and fiber fracture. These ana
lyses demonstrated that there exists an optimal forging speed at which
the consolidation stresses are a minimum. It was also shown that the
flow stress of the encapsulation material relative to that of the dens
ifying layup is an important consideration in achieving full consolida
tion during forging. Specifically, the difference in flow stress betwe
en the two materials influences the magnitude and sign of the in-plane
(secondary) stresses that are developed during forging and therefore
the rate of pore closure during the latter stages of the process. With
regard to fiber fracture, analyses were performed to estimate the axi
al and tangential stresses during rapid consolidation. The theoretical
work was validated by experimental trials using the Ti-14Al-21Nb matr
ix/silicon carbide fiber system. Measured forging pressures were in go
od agreement with predictions. Fiber fracture observations indicated t
hat tangential tensile stresses developed in the fiber control failure
; a forging window to avoid such failures was thus developed. Finally,
it was demonstrated that matrix microstructures and mechanical proper
ties similar to those of conventionally consolidated Ti-14Al-21Nb/sili
con carbide composites can be achieved by the forge-consolidation tech
nique.