Role of Ni Content on Microstructure, Mechanical Property, and In‐Site Local Corrosion Behavior of Welded Joints Produced by Laser Welding of Dual‐Phase Steel

Herein, the effects of Ni content on the microstructure, microhardness, and in‐site local corrosion behavior of laser‐welded joints in dual‐phase steel are investigated. The experimental results indicate that the microstructure of the fusion zone (FZ) changes from martensite to austenite as the Ni content increases. The FZ hardnesses of the 0Ni (no Ni foil addition) and 50Ni (50 μm Ni foil) welded joints are higher than that of the 100Ni (100 μm Ni foil) welded joints because of the austenite in the 100Ni welded joint. The welded joint without Ni shows severe pitting corrosion (more than 15 pitting sites in each zone of the welded joint) at the tested corrosion time. However, when immersed in the corrosion solution, the welded joints with added Ni exhibit slight pitting corrosion (less than five pitting sites). The Ni addition inhibits the pitting corrosion of the welded joints of high‐strength dual‐phase steel.