Microstructural characterization in dissimilar friction stir welding between 304 stainless steel and st37 steel

Dissimilar friction stir welding of duplex stainless steel to low alloy structural steel

“…greater hardness) was placed on the advancing side, 10 too great a traverse speed induced top surface groove-like defects due to lack of heat input, 14 and tool pin offset is an important factor to balance tool wear, material flow and weld penetration depth. 11,16 With supporting evidence that FSW could be applied to dissimilar materials, 1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] some focus was shifted towards dissimilar steel joints. Research in FSW of dissimilar ferrous alloys is immature and continuing to develop, unlike more traditional fusion welding processes.…”

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Extensive work has been carried out to demonstrate the advantages of FSW for a range of metals [24][25][26][27][28][29][30][31][32][33][34][35][36] and a growing amount of work for dissimilar alloys. 1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Results from FSW of dissimilar materials highlighted the viability of such a process with the majority of reports concluding that high quality, defect-free welds had been produced. Nevertheless, there were a few issues and considerations revealed; the level of material flow is closely linked to weld tool rotational speed, 8 high quality welds were produced when the material requiring t...…”

“…1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Results from FSW of dissimilar materials highlighted the viability of such a process with the majority of reports concluding that high quality, defect-free welds had been produced. Nevertheless, there were a few issues and considerations revealed; the level of material flow is closely linked to weld tool rotational speed, 8 high quality welds were produced when the material requiring the highest flow stress to induce thermo-mechanical deformation (i.e. greater hardness) was placed on the advancing side, 10 too great a traverse speed induced top surface groove-like defects due to lack of heat input, 14 and tool pin offset is an important factor to balance tool wear, material flow and weld penetration depth.…”

“…Reporting on the dissimilar welds, it was concluded that tensile strength was greater than the similar St37 weld, ductility was higher than either of the similar material welds, and that the microstructure of the AISI 304 stainless steel close to the weld interface presented little change as a result of the welding process. Published work on FSW of dissimilar steels is very sparse with Jafarzadegan et al 8 being one of the very few. This work reports on FSW of AISI 304 stainless steel to st37 steel at two different weld tool rotational speeds, 400 rpm and 800 rpm.…”

“…It was also suggested that the 304 stainless steel within the SZ recrystallised due to the hot deformation during the welding process in the austenite region, leading to transformation of the austenite grains to two different microstructures; ferrite and pearlite, and Widmanstatten ferrite with colonies of ferrite and cementite. 8 The SZ of the AISI 304 stainless steel displayed evidence of dynamic recrystallisation which was one of the reasons for the increase in hardness within the weld SZ, the other being the transformation of the st37 steel. Jafarzadegan et al 8 determined the yield strength (YS) and ultimate tensile strength (UTS) of the welds.…”