Effect of fine dispersoids on dislocation density and dislocation rearrangement of Al-Mn alloy during tensile deformation

In-situ neutron diffraction studies of changes in the dislocation density and dislocation rearrangement have been performed during tensile deformation of Al-1.14Mn-0.16Si-0.14Fe (mass%) alloy, which were homogenized at different conditions (sample-A: 350 degrees C for 60 h and sample-B: 500 degrees C for 4 h) for controlling size and number density of dispersoids. The sample homogenized at 350 degrees C shows finer size and higher volume fraction of dispersoids than those of the sample homogenized at 500 degrees C. An increase rate of the dislocation density and the yield stress of the sample homogenized at 350 degrees C are higher due to more effective short-range interactions controlled by dislocation pinning by dispersoids. The larger number of finer dispersoids leads to higher applied stress, proportional to the yield stress, required for dislocations to pass these obstacles in order to facilitate further plastic deformation. The presence of dispersoids leads to an inhibition of the dislocation cell wall formation induced by large dislocation accumulation during the deformation. The inhibition of the cell formation is indicated by a trend change of the dislocation rearrangement parameter from an increasing trend to a decreasing trend is observed at similar to 0.06 true strain for the sample-B and at similar to 0.1 true strain for the sample-A. The finer and larger number density of dispersoids caused longer delay in the formation of dislocation cell walls.