In this paper, bimetallic functionally graded structures were fabricated using wire and arc additive manufacturing (WAAM). The bimetallic walls were built by depositing Si-Bronze and high-strength low-alloy (HSLA) steel, successively. The microstructural evolution of the built structures, especially within the fusion zone between the dissimilar alloys, was investigated in relation to their mechanical properties. The built bimetallic walls showed a high level of integrity. An overall interface length of 9 mm was investigated for microstructural evolution, elemental mapping and microhardness measurements along the building direction. Microhardness profiles showed a gradual transition in hardness passing through the diffusion zone with no evidence for intermetallic compounds. Failure of the tensile specimens occurred at the Si-Bronze region, as expected. Bending tests confirmed good ductility of the joint between the dissimilar alloys. Direct shear test results proved a shear strength comparable to that of HSLA steel. The obtained results confirm that it is appropriate to fabricate HSLA steel/Si-Bronze FGMs using WAAM technology.

This paper introduces an active thermal management (ATM) system mitigating the thermal stresses associated with WA-DED of HSLA steel/CuSi/aluminum (Al) trimetallic structures. The study aims to regulate the formation of detrimental intermetallic phases at the CuSi/Al interface. Preliminary trials included quantitative porosity analysis and qualitative interfacial cracking inspection to obtain the appropriate processing parameters of Al-5356 on CuSi substrates. The developed ATM system enabled multi-layer deposition of trimetallic HSLA steel/CuSi/Al-5356 structures. Comprehensive microstructural analysis revealed a continuous 2 µm film of η-AlCu intermetallic phase along the CuSi/Al-5356 interface, and a 40 µm mixed zone of eutectic (α-Al + θ-Al ₂ Cu) and intermetallic phases. Hardness measurement along the building direction passing through the interface between CuSi and Al layers revealed an abrupt increase in hardness up to (350 HV), which confirmed the formation of hard intermetallic phase along the CuSi/Al interface. Tensile testing of the trimetallic material along the building direction revealed a significant reduction in strength and ductility compared to the transverse tested single material samples due to the induced influence of the brittle intermetallic layer formed at the CuSi/Al interface. Graphical abstract