Effect of heat treatments on interfaces of hot rolled Q235- TA2 clad plate with a niobium interlayer

The normalization process and high- temperature temper process were used to investigate the effect of heat treatments on the microstructure and mechanical properties of bond interfaces. The SEM and EDS were used to discuss the microstructure and element diffusion after heat treatment. And the interfacial bond strength was obtained by compression shear test on the testing machine. With the fractured surface morphology analysis, the composition of phases at the bond interface was analyzed by XRD. The experimental results show that a small quantity of brittle intermetallic compound Fe2Nb phases are observed at the bonding interface of the Q235- Nb bonds after heat treatment, and needle structure is formed at Nb- Ti interface after normalization treatment. The compression shear strength of normalized specimens(171MPa) at 900?? is slightly higher than that of the high- temperature tempered specimens(162MPa) processed at 650??. Observation of fracture surfaces demonstrations that the failure takes place through the bonding interface of the Q235- Nb bonds during all the shear tests, the compression shear strength is lower at Q235- Nb interface than at Nb- Ti interface.