| Titanium is an excellent light material with light weight,high strength and corrosion resistance,but as a rare metal,the price is high.Stainless steel has high strength and good plasticity,but stainless steel corrodes quickly in the presence of chloride ion.Titanium/stainless steel composite plate not only reduces the consumption of precious metal titanium to a great extent,but also shows excellent comprehensive properties,so it is widely used in chemical industry,electric power,petroleum,marine,aerospace and other important fields.It has been widely concerned by scholars at home and abroad.The titanium/steel clad plate prepared by traditional hot rolling method has high rolling temperature and high reduction rate,and the bonding interface is easy to form many kinds of brittle compounds such as Fe-Ti system and TiC,which seriously affect the bonding properties of the composite plate.The formation of brittle compounds of Fe-Ti system and TiC can be inhibited to some extent by adding intermediate layer,but new compounds will be formed and the production cost will be greatly increased.In order to solve the above problems,a method of titanium/steel rolling composite assisted by pulse current is proposed in this paper.the electroplasticity effect of pulse current is used to realize the preparation of titanium/stainless steel composite plate at lower temperature and lower reduction rate.In order to realize the stable application of current in the rolling process,the current application device is designed by using Solidworks three-dimensional software,and the finite element simulation analysis of the designed device is carried out by COMSOL Multiphysics.The results show that the upper and lower current density can be guaranteed to have a higher and more uniform current density in the rolling zone.In order to study the influence mechanism of pulsed current on the plastic deformation of metal materials,the heuristic mechanism of pulsed current rolling test was explored.The finite element simulation of 304stainless steel and TA1 pure titanium was carried out by using COMSOL Multiphysics finite element analysis software,and the pulsed current assisted tensile test was carried out.The results show that under the action of pulse current,the tensile strength and elongation at break of 304stainless steel and TA1 pure titanium decrease gradually with the increase of current density,which is due to the long action time of pulse current in the tensile process.The TC4/304 composite plate was prepared by using titanium alloy TC4 and 304stainless steel with the assistance of pulse current.The tensile shear test was carried out by Instron5969tester,and the bonding properties of the composite plate were tested.The interface microstructure and element distribution of titanium/steel composite plates prepared by different processes were analyzed by scanning electron microscope(SEM)equipped with energy spectrometer(EDS),and the phase of the bonding interface was determined by X-ray diffractometer(XRD).The results show that at 750?,the TC4/304 composite plate can be bonded and a higher shear strength can be obtained,and the bonding strength does not increase with the increase of the reduction rate.When the reduction rate reaches 58%,the bonding strength decreases sharply due to the holes produced by the Kirkendahl effect.At58%reduction,a good bond can be achieved at 650?,and with the temperature rising to850?,a large number of brittle compounds are formed at the interface to weaken the bonding strength.The pulsed current-assisted rolling test of industrial pure titanium TA1 and 304stainless steel without alloying elements was carried out at 750?.The results show that there is a similar rule between TA1/304 composite plate and TC4/304 composite plate,and the interface can be bonded at the reduction rate of 24.4%.However,the bonding strength of the interface Fe Ti and Ti Ni compounds and holes due to Kirkendall effect decreased sharply at the reduction rate of 54.4%.Furthermore,rolling experiments with different current densities were carried out under 41.6%reduction rate.The results show that the shear strength of the composite plate is the highest when the current density is 1.15A/mm~2,reaching 356MPa. |
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