Friction Stir Welding of Oxide Dispersion Strengthened Alloy MA956

Impact of friction stir welding on the microstructure of ODS steel

“…We have also detected a modest increase in the average particle size in all welds with respect to the base material, as have other studies on FSW of ODS steel [37][38][39]. In our study, the base material had been annealed at 1320°C for 1h prior to FSW.…”

“…The SZ grain structure coarsens from its initial sub-micron grain size, and becomes more equiaxed in the thermal wake of the tool in a static annealing process [40]. Another study on FSW of MA956 [38] showed that the grain size of friction stir welded MA956 is stable during post weld heat treatment at 1300⁰C for one hour. Given that the temperatures achieved in this work during FSW remained lower than 1000°C and that the exposure time during welding was below 1 min, the direct effect of the heat input on the matrix is unlikely to be the sole determining factor for the final grain size in MA956 after FSW.…”

Grain size and particle dispersion effects on the tensile behavior of friction stir welded MA956 oxide dispersion strengthened steel from low to elevated temperatures

“…Previous research on FSW of MA956 has shown that FSW is a viable joining mechanism that can produce consolidated welds in MA956 while maintaining a majority of the base material hardness [21,29,37]. Research on FSW with an initial fine grain size was shown to cause significant grain coarsening and softening in the weld nugget that was a function of the welding parameters [21].…”

Influence of Heat Input on Friction Stir Welding for the Ods Steel MA956

“…For example, no meaningful change in oxide particle size or distribution could be seen in backscattered electron images across the SZ/TMAZ interface for the 400 RPM/4 IPM condition, (Figure 2). It is well known that MA956 has both a microscale and a nano-scale oxide particle distribution and the results in this work cannot speak to changes in the nanoscale oxides [9,20]. Atom probe tomography (APT) measurements by other authors have concluded that the oxide particle size and distribution does not change much during FSW [7].…”

“…Based on the current literature, increasing the heat input during FSW of MA956 is expected to increase the grain size in the stir zone (SZ) while consequently lowering hardness [5,6,8,9]. The research results reported herein quantifies the heat input during FSW as a function of the tool rotational speed and tool traverse speed.…”