In-Situ Observation of Fracture Behavior of Ti-Aluminide Multi-Layered Composites Produced by a Hybrid Sintering Process

The fabrication of Ti-aluminide multi-layered composites have attracted great attention for their excellent mechanical properties, such as high specific strength, high specific stiffness, tolerable toughness, and low density. The preparation of the composite produced by a hybrid procedure composed of Vacuum Hot Pressing (VHP) and Hot Isostatic Pressing (HIP) using Ti foils and Al foils has been performed. Further, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-ray Spectrometry (EDXS) were carried out to identify the microstructure and phase formation of the composite. In addition, an in-situ three-point bending test was conducted on the notched specimen to observe the crack propagation behavior carefully. The results indicate that the densified composite was obtained without any apparent voids and pores which could undesirably develop into the source of cracks. Furthermore, all the pure Al foils were totally consumed to form a series of the Ti-Al compounds through the diffusive reaction between the adjacent Ti and Al foils. Moreover, the in-situ observation demonstrates the initiation and propagation of cracks in the intermetallic layers and the role of residual Ti layers to blunt and bridge the cracks by their plastic deformation. This study provides a new strategy for fabricating the Ti-aluminide multi-layered composites.