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Bimetal composites have wide applications due to their excellent overall performance and relatively low cost. In this study, the formability of stainless/carbon steel bimetal medium-thick composite in the stamping process without blank holder was investigated by finite element (FE) simulations and experiments. Uniaxial tensile tests on substrate metal (carbon steel) and clad metal (stainless steel) were first conducted, respectively, in order to obtain the material properties of each metal layer required in the FE simulation. Processing variables, including the layer stacking sequence, relative thickness ratios of two layers and friction conditions, were considered, and their effects on the magnitude of press load and distributions of thickness strain for predicting the high-risk region of necking during stamping were discussed. Experimental tests were carried out to verify the simulation results. It is indicated that simulation results can be used as an evaluation indicator to ensure the bimetal medium-thick composite can be safely formed. [ABSTRACT FROM AUTHOR]

• The unique hot flow behaviour of bimetal composite different from that of a single material was analysed. • A physically-based constitutive model considering DRV and DRX softening mechanisms for bimetal composite was established. • A mixture law of bimetal composite considering the strain and stress partitioning was developed. • Analytical, FE and experimental investigations were conducted on the flow behaviour of bimetal composite. The flow behaviour and strain partitioning of 2205 duplex ferritic-austenitic stainless steel/AH36 low carbon steel bimetal composite (2205/AH36 BC) were investigated at elevated temperatures in this study. A physically-based constitutive model was established to describe the flow behaviour of bimetal composite based on the stress–strain relationships obtained from hot tensile tests, which were performed on a Gleeble 3500 thermal-mechanical test simulator over the temperature range of 950–1250 °C and strain rate range of 0.01–1 s−1. The stress and strain partitioning of bimetal composite was analysed to develop a mixture law of flow stress under those hot working conditions, due to the different strain contributions of each material on the total flow behaviour of bimetal composite. The developed constitutive model and the mixture law considering strain partitioning were both adopted to predict the stress–strain curves and used in finite element (FE) simulation model to calculate the peak loads of 2205/AH36 BC at 1000 °C. It is found that the softening mechanisms of 2205/AH36 BC changes depending on the externally imposed working temperatures and strain rates. The contribution of AH36 carbon steel layer on total stress is relatively more than that of 2205 stainless steel layer at high temperatures, as a result of the occurrence of stress partitioning. The proposed constitutive model, instead of the mixture law, is recommended to be used in the FE simulation of practical hot working of bimetal composite due to its high accuracy. [ABSTRACT FROM AUTHOR]