Effect of physical and crystallographic properties on diffusion mechanism of copper and titanium sheets joined via explosion welding

In this study, ASTM C11000 commercially pure copper and Grade 2 commercially pure titanium sheets were joined by explosive welding using two different explosive ratios (R = 2.5 and R = 3.5) to produce Cu/Ti layered composites.The effects of the explosive ratio on the interfacial morphology, crystallographic characteristics, dislocation density, electrical conductivity, and thermal behavior of the composites were investigated.Microstructural and elemental analyses were performed using scanning electron microscopy (SEM) and energy--dispersive X-ray spectroscopy (EDS), while crystallographic characterization was conducted using X-ray diffraction (XRD).Differential scanning calorimetry (DSC) analyses were performed at heating rates of 5, 10, and 15 • C min -1 , and the apparent activation energies associated with the selected interfacial thermal event were calculated using the Kissinger method.Increasing the explosive ratio from R = 2.5 to R = 3.5 transformed the relatively flat Cu/Ti interface into a distinctly wavy morphology and resulted in the formation of island-like regions and a locally broadened interfacial interaction zone.The dislocation density increased from 1. × 10 15 to 2.1 × 10 15 m -2 with increasing explosive ratio.The composite produced at R = 2.5 exhibited approximately 25 % higher electrical conductivity than that produced at R = 3.5.The apparent activation energies were determined as 206 and 44 kJ mol -1 for R = 2.5 and R = 3.5, respectively.The lower apparent activation energy obtained at R = 3.5 indicates that the thermal process associated with the selected DSC peak occurs more readily at the highly deformed and defect-rich interface.These findings reveal a trade-off between interfacial deformation and electrical performance.R = 2.5 is more favorable when higher electrical conductivity and a relatively uniform interface are required, whereas R = 3.5 promotes a wavy interface and greater defect density at the expense of electrical conductivity.Therefore, the explosive ratio should be selected according to the required balance between interfacial morphology, electrical conductivity, and thermal response in Cu/Ti layered composites.