Microstructure, properties and temperature evolution of electro-pulsing treated functionally graded Ti-6Al-4V alloy strip

Microstructure, mechanical properties, electrical resistivity and temperature evolution of functionally graded Ti-6Al-4V alloy strips were processed under the electro-pulsing treatment (EPT) for 16 s and further studied by optical microscope, scanning electron microscopy, X-ray diffraction, electrical resistivity measurement, mechanical testing and consecutive temperature testing. Six kinds of microstructures were obtained on the single functional graded material (FGM) by different EPT parameters. The temperature evolution of each processing parameter was measured timely to be found low and different as a proof of the coupling of thermal and athermal effect in the FGM-EPT procedure. With increasing the frequency, the volume of beta phase increased gradually in general and re-dissolution both occurred. The ductility for sectional samples of FGM was enhanced to the maximum value, elongation to failure 27.8%, without compromising too much ultimate tensile strength and relevant tensile fracture behaviors were changed. The mechanism of microstructure change was discussed by the coupling of the thermal and athermal effect of EPT to decrease the thermodynamic barrier and influence the dislocations and atoms motion.