Time-dependent effects in transient liquid phase bonding of 304L and Cp-Ti using an Ag-Cu interlayer

One of the challenges for bimetal manufacturing is the joining process. Hence, transient liquid phase (TLP) bonding was performed between 304L stainless steel and Cp-Ti using an Ag-Cu interlayer with a thickness of 75 µm for bonding time of 20, 40, 60, and 90 min. The bonding temperature of 860 °C was considered, which is under the β transus temperature of Cp-Ti. During TLP bonding, various intermetallic compounds (IMCs), including Ti₅Cr₇Fe₁₇, (Cr, Fe)₂Ti, Ti(Cu, Fe), Ti₂(Cu, Ag), and Ti₂Cu from 304L toward Cp-Ti formed in the joint. Also, on the one side, with the increase in time, further diffusion of elements decreases the blocky IMCs such as Ti₅Cr₇Fe₁₇, (Cr, Fe)₂Ti, Ti(Cu, Fe) in the 304L diffusion-affected zone (DAZ) and reaction zone, and on the other side, Ti₂(Cu, Ag) IMC transformed into fine morphology toward Cp-Ti DAZ. The microhardness test also demonstrated that the (Cr, Fe)₂Ti + Ti₅Cr₇Fe₁₇ IMCs in the DAZ on the side of 304L have a hardness value of HV 564, making it the hardest phase. The maximum and minimum shear strength values are equal to 78.84 and 29.0 MPa, respectively. The cleavage pattern dominated fracture surfaces due to the formation of brittle phases in dissimilar joints.