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

Abstract

Tungsten (W) usually shows a high ductile-brittle transition temperature (DBTT). To overcome this shortcoming, 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 ℃. For uniaxial tensile tests, the DBTT of composites bonded at 1000 ℃ is about 200 ℃. However, the DBTT of composites bonded above 1200 ℃ is about 300 ℃. When testing temperature is lower than the DBTT, both the strength and ductility are improved with increasing temperature. The composites exhibit the highest tensile strength at 300 ℃. Meanwhile, the fracture modes of the composites, especially the W layer, changes dramatically at different testing temperature. For the composites bonded at 1000 ℃, the fracture mechanism of W layer changes from brittle cleavage fracture to delamination fracture, and then to ductile shear fracture. For the composites bonded at a temperature above 1200 ℃, 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.