Microstructural evolution in 4Cr_(10)Si_2Mo at the 4Cr_(10)Si_2Mo/Nimonic 80A weld joint by inertia friction welding

摘要

The microstructure evolution in 4Cr_(10)Si_2Mo at the weld joint of 4Cr_(10)Si_2Mo/Nimonic 80A formed by inertia friction welding was studied. It is discovered that the welds formed included three zones: thermo-mechanically affected zone (TMAZ); heat-affected zone and the matrix. The TMAZ comprised two regions: a chemical composition mixture zone (CMZ) and a pure shearing zone (PSZ). The austenite grain of the matrix in the CMZ sizing in 3-5 mu m contains large numbers of carbides with a size smaller than 50 nm. However, the grain size in PSZ is about 8-10 mu m. The dislocation density in this zone is much lower than that in CMZ. The carbides in PSZ were mainly distributed at grain boundaries or on shear band. In some locations of high dislocation density, clusters of pearlite of hundreds of nanometers precipitated from the dislocation networks. Grain size in the heat-affected zone is similar to that in the as-received 4Cr_(10)Si_2Mo.