The Effects Of Current Pulse On Microstructures And Propertiesof Titanium And Titanium Alloys

Based on the electroplasitic effect of metal materials,the uniaxial tensile experiments of TA1 pure titanium,TB2 titanium alloy and TC4 titanium alloy were conducted under the pulsed current,and to explore the influence of electroplasitic effect on mechanical properties and microstructure of materials by changing the parameters of pulse current.The experiments results show that:(1)when the uniaxial tensile experiments are under the effect of pulse current,the tensile strength of TA1 titanium has a significant reduction,the elongation does not increase but decreases,and the surface hardness slightly declines,comparing with the tensile experiments without pulse current.When the current is 20 A and duty radio is 5%,the tensile strength declines by 62.7%,the elongation reduces by 13.9% and the surface hardness decreases by 9.7%;(2)For TB2 titanium alloy,the tensile strength decreases greatly,the elongation increases,and the surface hardness decreases.When the current is 20 A and duty radio is 5%,the tensile strength of TB2 titanium alloy and TC4 titanium alloy decreases by 63.9%,the elongation increases by 7%,and the surface hardness decreases by 11.4%;(3)Also for TC4 titanium alloy,the tensile strength decreases greatly,the elongation increases,and the surface hardness decreases.When the current is 20 A and duty radio is 5%,the tensile strength of TC4 titanium alloy decreases by 78.1%,the elongation increases by 8.1%,and the surface hardness decreases by 15.5%.The electrothermal effect of current also can enhance the mechanical properties of materials,so the constant temperature tensile experiments of TB2 titanium alloy and TC4 titanium alloy are conducted to compare and analyze the influence of pure current effect and electrothermal effect on the properties of materials under the action of pulse current.Through the constant temperature tensile experiments,it is found that the reduction of tensile strength and the increase of elongation in material are significantly lower than that of the pulsed current group.Compared with pulsed current works,the tensile strength of TB2 titanium alloy and TC4 titanium alloy decreased by 39.3% and 45.8%,and the elongation decreased by 5.2% and 5.1%.The influence of electrothermal effect on material properties is always lower than that of pure current effect,so the effect of pure current on the properties of materials is more predominant.Combined with the observation on the microstructure of materials,it is found that the grains of TA1 pure titanium are coarsened under the action of pulsed current,and the arrangement of grains have a parallel orientation.The fracture morphology changes from the original ductile fracture to partial brittle fracture characteristics,which reflect the reduction of plasticity property.The fine grains of β phase of TB2 titanium alloy grow by recrystallized grain combination under the action of pulse current,and the distribution of β phase are more uniform,and the fracture morphology has more large and deep dimples,which reflect plasticity property lifting.Under the action of pulse current,the TC4 titanium alloy undergoes dynamic recovery and recrystallization to promote the transformation of α phases to β phases,and the β phases are connected to each other to form a more uniform bidirectional structure of α + β phase,and has larger dimples in the fracture morphology,which reflected plasticity property lifting.