Microstructure and mechanical properties of explosively welded joints between 06Cr18Ni11Ti stainless steel tube and Ti–4Al–2V alloy rod

The reliable joining of titanium and stainless steel is critically important, as these two materials are increasingly integrated in advanced industrial applications. In this work, a tubular composite rod was fabricated by explosive welding (EXW) between a 06Cr18Ni11Ti stainless steel tube and a Ti–4Al–2V alloy rod. Multi-scale characterization techniques, including SEM, EBSD, TEM, and microhardness testing, were employed to examine interfacial microstructural evolution, bonding mechanisms, and mechanical properties. The welded interface exhibited a corrugated morphology with a thin diffusion layer (∼260 nm). This layer formed through solid-state diffusion and localized eutectic reactions, producing amorphous phases and nanocrystalline Ti–Fe intermetallic compounds (IMCs). Interfacial shear testing revealed a maximum strength of 482 MPa, with fracture preferentially initiating in IMC-rich vortex regions acting as stress concentrators. Fractography confirmed predominantly brittle failure characterized by cleavage planes and fragmented IMCs, with localized ductile features near the IMC zones. The interfacial hardness on the stainless steel side increased markedly from 228 HV to 405 HV owing to the formation of strain-induced α′-martensite, deformation twins, and high-density dislocations, whereas the titanium side remained essentially unchanged. Compared with previously reported Ti/Fe plate joints, this work is the first to systematically investigate a tubular/rod-type Ti/Fe EXW joint, revealing interfacial microstructure–property relationships and extending the applicability of EXW to geometries more representative of engineering components.