Effect of annealing on microstructure, shear and tensile strength of diffusion bonded FeCrAl/Zy4 clad plate

Abstract

The FeCrAl/Zy4 bi-layer clad plate was fabricated by solid diffusion, hot rolled and annealing treatment. The interface microstructure and phase analysis, texture, shear and tensile strength of the clad plate were investigated in details. The diffusional interface of clad plate was tightly bonded, and there were no cracks and pores. The intermediate phases formed at the interface region of the plate were identified as αZrCr2, ZrFe2 and Zr3Al. In addition, Zr3Fe formed at the interface of the sample annealed at 600 °C for 3 h (A63) and the sample annealed at 600 °C for 5 h (A65). For A65 samples, the texture of FeCrAl alloy is <111>∥ND, and a small part of <101>∥RD and <101>∥TD, the texture of Zy4 alloy are mainly <0001>∥ND, and a small part of <101¯0>∥RD and <112¯0>∥RD. These textures are favorable for plastic deformation of A65 samples. The optimal annealing process is 600 °C for 5 h, the sample has good comprehensive properties, shear strength 202 MPa, tensile yield strength 169 MPa, tensile utimate strength 563 MPa and fracture elongation 29%. The shear fracture surface of Zy4 alloy in A65 sample showed a mixture of dimple and brittle features. The fracture of FeCrAl alloy in the A65 sample shows ductile feature, while the Zy4 alloy side near the interface shows mixed fracture, and the region far away from the interface shows ductile fracture. The results in this study could provide possible valuable guidance for fabricating double or multilayer fuel cladding materials for the application in the nuclear reactor.