The ductile-brittle transition behaviors of W/Ta multilayer composites

Tungsten (W) usually shows a high ductile-brittle transition temperature (DBTT). To overcome this short-coming, W-based multilayer composites have been designed. In this study, the ductile-brittle transition behaviors of W/Ta multilayer composites are investigated by uniaxial tensile and three-point bending tests under temperatures ranging from room temperature to 600 degrees C. For uniaxial tensile tests, the DBTT of composites bonded at 1000 degrees C is about 200 degrees C. However, the DBTT of composites bonded above 1200 degrees C is about 300 degrees C. When testing temperature is lower than the DBTT, both the strength and ductility are im-proved with increasing temperature. The composites exhibit the highest tensile strength at 300 degrees C. Meanwhile, the fracture modes of the composites, especially the W layer, changes dramatically at different testing temperature. For the composites bonded at 1000 degrees C, the fracture mechanism of W layer changes from brittle cleavage fracture to delamination fracture, and then to ductile shear fracture. For the com-posites bonded at a temperature above 1200 degrees C, the fracture mode of W layer evolves from intergranular fracture to cleavage fracture, then to shear fracture. Compared with uniaxial tensile tests, the DBTT is lower during three-point bending. (c) 2023 Elsevier B.V. All rights reserved.