Effect of Ni Coating on Microstructure and Property of Al Alloy/Steel CMT Welding-Brazing Joints

The cold metal transfer (CMT) welding-brazing process was chosen to join Al alloy and Ni-coated steel using AlSi12 as the filler wire. macrostructure microstructure of joints were tested by an optical microscope (OM), scanning electron (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD). tensile properties corrosion also tested. results showed that Ni coating could improve wettability spreadability molten on surface, resulting in a good appearance for alloy/steel joint. hinder chemical metallurgical reaction between atom Fe atoms inhibit formation brittle Fe-Al intermetallic compounds (IMCs) reduce thickness IMCs layer. Meanwhile, reacted with form Al3Ni2, (Fe, Ni) Al3 Ni)2Al3, which improved strength joints. All cracked near alloy. When Ni-coating 5 μm, joint reached maximum 202.5 MPa. addition resistance Significantly, when 10 most still solid, interface layer mainly composed α-Ni solid solution some Ni)2Al3.