Effect of bonding temperature on tensile behaviors and toughening mechanism of W/(Ti/Ta/Ti) multilayer composites

Abstract The inherent low-temperature brittleness has restricted the application of tungsten materials. One option for enhancing the tungsten fracture toughness is to use tungsten-based layered composites. In this study, W/(Ti/Ta/Ti) multilayer composites with the application of spark plasma sintering under varying bonding temperatures from 1,000 to 1,400°C were fabricated. The ambient- and high-temperature tensile mechanical performance of W/(Ti/Ta/Ti) samples is investigated to obtain the correspondence of microstructure to tensile performance. The as-fabricated composites exhibit significantly superior comprehensive tensile performance to the original foil. When bonded at 1,200°C, the comprehensive tensile performance of W/(Ti/Ta/Ti) samples is the best, showing an elongation of 5.0% and a tensile strength of 671 MPa. The bonding temperature leads to microstructural changes in the as-fabricated composites, thereby affecting their high-temperature tensile mechanical properties. When bonded at 1,000°C, the ductile–brittle transition temperature (DBTT) is approximately 100°C. When bonded at 1,200°C, the DBTT is approximately between 100 and 200°C. When bonded at 1,400°C, the DBTT is between 100 and 200°C. For W/(Ti/Ta/Ti) multilayer composites having low interfacial bonding strength, the primary energy dissipation modes include intermediate-layer plastic deformation, multi-tunnel crack propagation in the W layer, as well as W/Ti interfacial delamination. As for W/(Ti/Ta/Ti) multilayer composites having high interfacial bonding strength, energy can only be consumed through the principal crack propagation. Meanwhile, a tensile strength model is constructed based on the stress concentration coefficient after the nucleation of microcracks at the W/Ti interface.