Optimization Mechanisms of Microstructure and Mechanical Properties of SiC Fiber Reinforced Ti/Al3Ti Laminated Composite Synthesized Using Titanium Barrier

Abstract

A novel structure-optimized SiC fiber reinforced metal-intermetallic-laminated composite (SiCf-Ti/Al3Ti) without intermetallic centerline defect has been fabricated by vacuum hot pressing using stacked fibers and foils as well as Ti barrier layer. Through microstructure characterization by SEM and EBSD, the mechanisms of centerline formation and structural optimization were investigated detailedly. The mechanical properties and fracture behaviors of the optimized and non-optimized SiCf-Ti/Al3Ti composites were studied via quasi-static compression tests. The experimental results indicated that the intermetallic centerline region existing at the mid-plane of Al3Ti layer in non-optimized composite mainly contains newly-formed Kirkendall voids and gathered metallic oxides. Additionally, owing to the similar moving trails of fibers, oxides and voids in molten Al during hot pressing, SiC fiber is always accompanied with centerline, which causes the poor bonding of SiCf/Al3Ti interface. Unlike that, due to the adding of Ti barrier layer, SiC fibers are separated from centerline and metallurgically bonded with Al3Ti intermetallic in the optimized composite. The compression testing results proved that the optimized SiCf-Ti/Al3Ti composite possesses superior strength and toughness compared with those of the non-optimized composite. Besides, the extending of cracks along centerline often leads to large-scale centerline splitting and untimely SiCf/Al3Ti interface debonding in non-optimized composite. Nevertheless, cracks formed in optimized composite tend to propagate at the interfacial zone between layers instead of cutting off Al3Ti layer along its mid-plane. Moreover, ascribed to the well-bonded SiCf/Al3Ti interface, SiC fibers play an important role in strengthening and toughening the optimized SiCf-Ti/Al3Ti composite by fiber bridging mechanism.