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

Abstract

FeCrAl/Zy4 clad plates were fabricated by solid diffusion at 850 °C for 5 h under mechanical pressure in argon atmosphere, and hot rolling at 800 °C with a reduction of 22%, 30%, and 52%. The hot-rolled clad plates were annealed at 700 °C for 0.5–3 h and were well-bonded. The αZrCr2, ZrFe2 and Zr3Al phases formed at the interface of the annealed sample. Further, Zr3Fe formed at the interface of the 22% rolled sample annealed at 700 °C for 1 h (2A7-1). The empirical formula for αZrCr2 and ZrFe2 was determined to be Zr(Cr,Fe)2 Laves phase by TEM characterisation. The size of the Zr(Cr,Fe)2 Laves phase was ~55 nm. The texture of the FeCrAl side of the 30% rolled sample annealed at 700 °C for 1 h (3A7-1) was mainly <111>//ND, whereas that of the Zy4 side was predominantly <0001>//ND with a small proportion of <101¯0 > //RD and < 112¯0 > //RD. These textures are favourable for the plastic deformation of the Zy4 alloy side in the 3A7-1 sample. The 52% rolled sample annealed at 700 °C for 1 h (5A7-1) exhibits good comprehensive properties, i.e. shear strength: 189 MPa, shear strain: 8%, tensile yield strength: 187 MPa, ultimate tensile strength: 556 MPa, and fracture elongation: 33%. The shear strength increased with the average thickness of the diffusion layer. The shear fracture surface of the Zy4 side exhibited a mixture of dimples and brittle features. The fracture of the FeCrAl side in the 5A7-1 sample is a ductile feature, whereas the Zy4 alloy side near the interface is a quasi-cleavage fracture, and the region far away from the interface is a ductile feature. The results could provide valuable insight for the design and fabrication of the bilayer or multilayer fuel cladding materials for application in nuclear reactors.