Grain refinement by means of phase transformation and recrystallization induced by electropulsing

The specimens cut from as-cast TiAl alloy and cold-rolled TA15 sheet were treated by high density electropulsing. The optical microscope (OM) and transmission electron microscope (TEM) were used to examine the changes of the microstructure before and after the electropulsing. It is found that fine and homogeneous microstructures with the grain size of 30-50 μm can be obtained from the as-cast TiAl based alloy with the initial lamellae of about 1 000μm. The electropulsing treatment can induce the completed recrystallization in cold-rolled TA15 sheet. After electropulsing treatment, the microstructure of TA15 sheet transformed from primary α laths grain to smaller α equiaxed grain. The research results show that the electropulsing treatment is an effective method to refine grain of as-cast TiAl alloy and cold-rolled titanium alloys sheet. Because the conventional thermo-mechanical processing such as forging or extrusion or rolling as well as heating are not required, the refining process by electropulsing is simpler than conventional ones.