Influence of holding time on microstructure and mechanical properties of 20G/316L dissimilar metal TLP welded joints

The amorphous Ni foil was used as the intermediate layer material. The transient liquid phase diffusion（ TLP） connection experiment was carried out on 20 G/316 L stainless steel by high frequency induction heating system. The microstructure,element diffusion and migration of the joint’s interface and the mechanical properties were studied. The results show that when the welding temperature is 1 120 ℃ and the holding time is 30 ～ 60 min,good metallurgical bonding can be achieved between 20 G carbon steel and 316 L stainless steel. During the welding process,carbides precipitated in the stainless steel side matrix. With the extension of holding time,the austenite-like structure is gradually formed. In a short holding time,the Ni element in the middle layer preferentially diffuses toward the stainless steel side to form a diffusion-dissolving layer of a certain width. As the holding time increases,carbon steel side interface appears bending and the interdiffusion flux of the interface element increases. When the holding time increases to 50 min,the interface element diffuses sufficiently,the fine austenite microstructure regenerates,and shear strength of the joint reaches a peak（ 351 MPa）.