Indentation of titanium processed by equal channel angular pressing

Commercially pure titanium rods were processed by equal channel angular pressing (ECAP) to obtain an ultrafine-grained microstructure. The titanium rods were extruded for 2 passes at 623 K, using three different bending angles of 90°, 120° and 150°. For the bending angle of 90°, the titanium rods were extruded for 4 and 8 passes in addition to 2 passes. The microstructure of the ECAP-processed titanium was evaluated using the TEM technique. The bending angle had a strong effect on the grain refinement, while the number of pressing passes did not have a noteworthy effect on the evolution of the microstructure. Microindentations were conducted with the indentation load in the range 100-2000 mN. The indentation hardness decreased slightly with the increase in the indentation load. The titanium processed by the die with a bending angle of 90° had the highest indentation hardness. The energy ratio of the plastic energy to the total energy was found to be proportional to the ratio of the residual indentation depth to the maximum indentation depth.