Microstructural characterisation of stir zone containing residual ferrite in friction stir welded 304 austenitic stainless steel

Abstract

Friction stir welding was applied to a 2 mm thick 304 austenitic stainless steel plate. The microstructural evolution and hardness distribution in the weld were investigated. The stir zone (SZ) and thermomechanically affected zone (TMAZ) showed dynamically recrystallised and recovered microstructures, respectively, which are typically observed in friction stir welds in aluminium alloys. The hardness of the SZ was higher than that of the base material and the maximum hardness was observed at the TMAZ. The higher hardness at the TMAZ was attributed to high densities of dislocations and subboundaries. Microstructural observations revealed that the ferrite was formed along grain boundaries of the austenite matrix in the advancing side of the SZ. It is suggested that the frictional heat due to stirring resulted in the phase transformation of austenite to ferrite and that upon rapid cooling the ferrite was retained in the SZ.

High Speed–High Quality Friction Stir Welding of Austenitic Stainless Steel

“…A number of authors have shown the possibility of friction stir welded high temperature materials of Mo, 12) Ti, 13,14) IF steel 15) and carbon steel, [16][17][18][19] etc. There are some reports [20][21][22][23][24][25][26][27][28][29] on the friction stir welding of austenitic stainless steel. Though these research studies mainly reported the characteristics of corrosion [20][21][22] or the microstructures and mechanical properties.…”

“…There are some reports [20][21][22][23][24][25][26][27][28][29] on the friction stir welding of austenitic stainless steel. Though these research studies mainly reported the characteristics of corrosion [20][21][22] or the microstructures and mechanical properties. [23][24][25][26][27] There are only few reports of the welding condition effects on the joint strength.…”

Microstructure, Mechanical and Corrosion Properties of Friction Stir Welding High Nitrogen Martensitic Stainless Steel 30Cr15Mo1N

“…As a result of the specific metal flow and stress distribution, a band structure with lamellar and streamline structure can be observed at the region surrounding the boundary of TMAZ/SZ-AS (Figure 2d). Some other studies also found this phenomenon [28][29][30][31]. Additionally, the interface (Figure 3c), it can be indicated that the precipitates are mainly carbides and nitrides rich in chromium.…”

Microestrutura de uma Solda Dissimilar entre o Aço Inoxidável Ferrítico AISI 410S e o Aço Inoxidável Austenítico AISI 304L Soldado pelo Processo FSW

“…Os autores consideraram que o refino de grão neste caso foi ocasionado pela grande deformação plástica causada pelo ombro da ferramenta. Esta deformação plástica juntamente com a alta temperatura experimentada é responsável pelo fenômeno de recristalização dinâmica do qual resulta a formação de grãos finos e equiaxiais [24,25]. …”