The 21-4N austenitic steel and the 4Cr9Si2 martensite steel were joined successfully by using inertia friction. In the process of inertia friction, the 4Cr9Si2 matrix on the welding surface precipitates along the 21-4N austenite grain boundary, forming the "bite" effect, which promotes metallurgical bonding. The peak temperature of inertia friction welding interface can reach above 1487K, and recrystallization, element diffusion and grain refinement exist in the weld center zone. In the tensile test, the fracture of the welded sample is in the 21-4N shear deformation zone, the maximum tensile strength is 1057MPa, and the elongation is about 12.5%. The 21-4N and 4Cr9Si2 dissimilar metals can be welded by inertia friction welding to obtain a joint structure with excellent performance.
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