Study On Surface Modifications Of Pure Titanium And Titanium Alloys By High Current Pulsed Electron Beam

High current pulsed electron beam(HCPEB) has been developed intensively as a new high-power energetic beam used for surface modifications of materials in recent years. The rolling technology was emerged in the last century. In the present work, pure Ti(TA2) and Ti alloys(TC2 and TC4) were selected to be treated with a method combining rolling and HCPEB to investigate the effect of the duplex treatments on their microstructures, phase components, hardness and corrosion resistance. The main conclusions are as follows:1. After the HCPEB treatment, the surface of pure Ti, TC2 and TC4 Ti alloys is α’ phase induced by α to b and then to α’ martensitic transformation due to HCPEB treatments. After the HCPEB treatments, craters appeared on the pure titanium and titanium alloys. With increasing the pulse number of HCPEB, the density of craters decreased.2. The texture modifications in pure titanium and titanium alloys by HCPEB were observed. Based on XRD analyses, the diffraction intensity of α(100) plane increased with the increasing number of pulses while the intensities of α(002) and α(101) planes weakened.3. The pure titanium and titanium alloys were hardened after rolling through deformation strengthening. However, the hardness of the pure titanium, TC2 and TC4 titanium alloys decreased after the HCPEB treatments due to the removal of residual stresses and the formation of soft martensite in the surface layer.4. The corrosion resistance of pure Ti can be improved by rolling and HCPEB treatments. With the increasing of rolling deformation, the corrosion resistance increased. The best corrosion resistance of pure Ti was achieved when the rolling deformation is 70%. When the deformation in pure titanium was kept constant, the pulses number of 5 times gave the best corrosion resistance. Under the electron beam treatment of 5 pulses, with increasing the rolling deformation, the corrosion resistance of pure titanium became better. For instance, when the deformation was 70% and pulses number was 5, the corrosion current density is 245.3 m A/cm2. When the number of pulses increased, the grain in the surface layer would grow larger and the corrosion resistance decreased.5. The corrosion resistance of TC4 was significantly improved after HCPEB treatments. When the number of electron beam pulses on the TC4 titanium alloy was 5 pulses and 10 pulses, Ecorr of the samples was increased from-682.5m V for the untreated sample to-297.5m V and-342.3 m V, respectively. At the same time, the corrosion current density decreased from 1028.1 m A/cm2 for the untreated sample to of 382.0 m A/cm2 for the 5 pulses treated sample. The Ecorr of TC2 was improved from-625.7m V for the as-received sample to-163.5m V for the 10 pulses treated sample. The corrosion current density was reduced to 343.3 m A/cm2 for the 5 pulses treated sample. The results indicated that the corrosion resistance of pure Ti and Ti alloys was improved by rolling and HCPEB treatments of 5 pulses, which was attributed to the homogenization, grain refinement and surface cleaning induced HCPEB treatments.