Fracture toughness of TiB reinforced Ti3Al2.5V composite prepared by the combination of high-energy ball milling and hot isostatic press followed by reactive sinteringWednesday (08.11.2017) 17:40 - 18:00 Part of:
Titanium Matrix Composite materials (TMCs) are highly expected as the aerospace materials with their high specific stiffness and fatigue properties among Metal Matrix Composite (MMCs). However, the few elongation and small fracture toughness of TMCs interrupt the practical realization of TMCs as the aerospace materials. We recently demonstrated good tensile strength of TiB reinforced Ti-based (Ti?TiB) composite, and it was implied that our Ti-TiB composite can have a good fracture toughness. In this study, we fabricated TiB reinforced Ti3Al2.5V (Ti3Al2.5V?TiB) composite, by the combination of high-energy ball milling, hot isostatic press and reactive sintering. Ti3Al2.5V and TiB2 powder were employed as the starting materials. The quantity of TiB2 powder was controlled to obtain Ti3Al2.5V?7.5, 10, 12.5 vol % TiB composite as the final composite. The mixed powder was encapsulated in a steal can and vacuumed at 500 ?. This vacuum-encapsulated powder was densified by the Hot Isostatic Press (HIP) at 920 ? for 2 hours under the pressure of 140 MPa. After removing the steal can from the densified Ti3Al2.5V + TiB2 precursor, this precursor was heat-treated at 1200 ? for 4 hours to form TiB particles inside composite. We finally obtained Ti3Al2.5V?TiB composite with the size of 11×11×70 mm3, from the cylindrical bulk with the size of f120300 mm3. We prepared Single Edge Notched Beam (SENB) specimens with the dimension of 5×10×50 mm. Also, the fatigue pre-crack was introduced before fracture toughness test. We performed 4-point bending test to estimate crack extension by using compliance method. We estimated the plane-strain fracture toughness (KIC) of Ti3Al2.5V?TiB composite, and revealed that the KIC of Ti3Al2.5V?TiB composite is constant. The observation of the microstructure of Ti3Al2.5V?TiB composite by Scanning electron microscope (SEM) and transmission electron microscope (TEM) implies that the shape of this R curve can be improved by the optimization of the microstructure of Ti3Al2.5V?TiB composite.