In-situ observation of dislocation motion and its mobility in Fe-Mo and Fe-W solid solutions at high temperatures

The mobilities of the edge dislocations in Fe-W and Fe-Mo solid solution alloys ai high temperatures were investigated with in-situ TEM observation in order to compare the effect of W and Mo on the solid solution hardening of ferrite. The dislocation behaviors were recorded continuously with VTR. TEM observations showed that the dislocations werfe moving viscously and that the dislocation velocites were constant in both Fe-W and Fe-Mo alloys. These results show that dislocations dragged solute atmosphere. The mobilities were determined to be 5.7xlO^-15m/(Pa·s) at 993 K in the Fe-W alloy and 4.3xlO-15m/(Pa·s) at 1 011 K in the Fe-Mo alloy. It was found that the mobility in the Fe-W alloy is similar to that in the Fe-Mo alloy. Mobilities were estimated by simulation using the interaction between an edge dislocation and solute atoms. The results show that the simulated value was similar to the measured value in the Fe-Mo alloy while the simulated value is different from the measured in the Fe-W alloy. The simulated mobility of the dislocation in Fe-W is one-tenth as large as that in Fe-Mo. The simulated results for Fe-W did not agree xvith the experimental results. It is considered that the difference between the experimental values and simulated values chiefly came from the shape of the dislocations using for measurement and the diffusion constant which was used in the simulation. Experimental results showed that the mobility in Fe-W is as large as that in Fe-Mo, Therefore, it is suggested that the effect of W on the solid solution hardening of Fe is similar to that of Mo.