Thermal expansion anisotropy in a Ti–6Al–4V/SiC composite

We studied the thermal expansion behavior of a Ti–6Al–4V/35 vol.% continuous SiC fiber composite using in situ high temperature neutron diffraction (ND). The lattice expansion of constituent phases within the composite was monitored from axial (parallel to the unidirectionally aligned fibers) and transverse (perpendicular to the fibers) directions during heating from room temperature (RT) to 1170 K. The phase-specific thermal expansion of the Ti–6Al–4V matrix and SiC fibers in the composite is discussed in the context of thermal load partitioning between the matrix and fibers. In the axial direction, the matrix and the fiber share the thermal load and co-expand up to about 800–900 K, above which the thermal load transfer becomes ineffective. In the transverse direction, the matrix and fibers expand independently over the whole temperature range. Using the Schapery model (J. Comp. Mater. 2 (1968) 380) and the rule-of-mixtures (ROM), the macroscopic thermal expansion of the composite is predicted and compared with the experimental results.