Microstructure and property inhomogeneity investigations of bonded Zr/Ti/steel trimetallic sheet fabricated by explosive welding

Abstract

Compared to Ti/steel bimetallic sheets, Zr/Ti/steel trimetallic sheets have improved service performance in severely corrosive environments because the corrosion resistance of zirconium and titanium are complementary. The inhomogeneities of the microstructure and mechanical properties as well as the underlying mechanism of the interactions in the Zr/Ti/steel trimetallic composite sheets fabricated by explosive welding were investigated. The shear strength of the Ti/steel interface and Zr/Ti interface was found to be anisotropic and isotropic respectively, which could be explained by the wide and unambiguous wavy morphology of the former and relatively narrow and obscure wavy morphology of the latter. A transient strain field on the bending specimen was achieved through the digital image correlation (DIC) method during a bending test and it was found that the change of von Mises strain across the Ti/steel interface was much more significant than that across the Zr/Ti interface. This could be related to the through-thickness heterogeneous mechanical properties verified by Vickers hardness tests and tensile tests of the stratified samples of the Zr/Ti/steel plate. Large blocks of FeTi intermetallic compounds were formed in the local melted zone (LMZ) at the Ti/steel interface, while uncoordinated plastic deformation across the interface resulted in the failure appearing at the Ti/steel interface during the bending test. Importantly, the values of shear strength and impact energy of the studied Zr/Ti/steel sheet met the requirements of ASME S264.