Microstructure and mechanical properties of additive manufactured steel-Al structure materials with nickel gradient layers

The microstructure and mechanical properties of steel/Al structure material produced by additive manufacturing (AM) was investigated in this work based on the cold metal transfer welding. The results show that the microstructure gradually changed from the steel side to the aluminum side. The microstructure in the steel layer consisted of vermiform like δ ferrite and austenite structure, while in the aluminum layer the microstructure was constituted by α-Al grains and typical reticulate distributive Al-Si eutectic structure. Besides, a 7 μm thickness Ni-Al intermetallic compound layer was emerged at the interface of nickel and aluminum layer. The maximum room-temperature tensile strength of the Steel-Al structure materials was found to be 54 MPa, the rupture morphology showed a brittle fracture characteristic.