Experimental and numerical investigations on the microstructural features and mechanical properties of explosively welded aluminum/titanium/steel trimetallic plate

In this paper, 3A21Al/TA1/CCSB composite plate was fabricated successfully by explosive welding to improve the bond strength. The microstructure characteristics of aluminum/titanium and titanium/steel bonding interfaces were systematically investigated by two-step numerical simulation and SEM/EBSD characterizations. Firstly, the SPH (Smoothed Particle Hydrodynamics) and Lagrange methodology were used to simulate and calculate the collision velocity and collision angle, establishing an accurate impact condition. Secondly, the SPH model was used to simulate the high-speed oblique impact welding process. The simulation results reproduce the formation of wavy interface, vortex zone and jet, which are consistent with the experimental results. Combined with SEM, EBSD, and EDS analysis, continuous and uniform wavy structures were found at different interfaces of the composite plate, showing significantly different wave lengths and amplitudes. Dynamic recovery and recrystallization took place at the bonding interfaces which showed refined grain with different preferred orientations. The observed structural characteristics and the thermodynamic state predicted by SPH simulation inferred the evolutions of microstructures (including morphologies, micro defects, grain structures). The tensile strength and fracture elongation of the trimetallic plate reach 448.2 MPa and 14.15%, respectively. In addition, the shear strengths of each interface far exceed the corresponding acceptable standard values.