1990 Volume 76 Issue 2 Pages 278-285
The effect of hot-pressing conditions such as temperature, time and pressure on the tensile strength of B/Al (1100) composite was investigated quantitatively. The B/Al (1100) composites were prepared invacuum by hot-pressing the sandwiches composed alternately of boron fibers and the thin plates of aluminium. The reaction products at the interface of B/Al were identified by X-ray diffraction and transmission electron microscopy (XRD and TEM). This indicates that the (100) plane of α-AlB12 crystal formed with the interfacial reaction reaction orients in parallel with the aluminium plane at the interface of B/Al. Increasing press temperature, time and pressure led to the degradation of the tensile strength of the B/Al (1100) composite due to the growth of the α-AlB12 phases.
The rule of mixtures was successfully applied to the tensile strength of the B/Al(1100) composite, on the assumption that the notches which were formed by fracture of the α-AlB12 phases caused loss of the tensile strength of boron fibers. The dependence of the tensile strength (σc) of the B/Al (1100) composite on press temperature (T) and time (t) can be expressed by the following equations :
σc=(2Eγs/πX)1/2 Vf + σm( 1-Vf ) (Pa)
X={2 × 10-8 × exp (-16 000/ T) ×t}1/2 (m)
where E is the Young's modulus, γs the surface energy of boron fiber, Vf fiber volume fraction, σm the tensile strength of aluminium and X the thickness of the α-AlB12 phase.
