Study On The Compression Deformation Mechanisms Of Ti-55531 Alloy At Room Temperature

High strength-toughness titanium alloys have many advantages,for instance,low density and good corrosion resistance the same as traditional titanium alloys.High strength-toughness titanium alloys have its own advantages of high tensile strength and low elastic modulus.Therefore,the high strength-toughness titanium alloys are mainly used in the structural parts of aviation,aerospace,marine and national defense.The chemical composition of high strength-toughness titanium alloys is very special because of a large number of beta stable elements have been added to them.So other special deformation mechanisms may also occur besides the slip and twin under the room temperature load.These special deformation mechanisms include stress-induced martensitic and omega transformation.The study on the deformation behavior of high strength and toughness titanium alloy at room temperature is beneficial to reveal the deformation coordination mechanism of high strength and toughness titanium alloy them under the service environment.The results provide basic guidance for the microstructure design and control the deformation mode during the service of the alloys.In addition,the results also could provide a basic information for the study of damage behavior in the service process of them.Ti-55531 alloy is selected as the research object in this paper.Diffeerent heat treatment processes are designed.The content of the alpha phase is changed to adjust the content of the beta phase.Thus,the stability of the beta phase is adjusted.We carried out this experiment using Gleeble 3800 and 6.3MN fast forging machine at different strains and strain rates at the room temperature circumstance.Samples were sampled at different strains.The Instron 5895 experiment machine was used to finish the tensile test at room temperature.The sample is obtained at the maximum area of the fracture in the vicinity of the fracture.We analyzed the microstructure of the alloy under different strains by OM,SEM,XRD,TEM and EBSD in order to study the deformation mechanisms.We found that the whole beta tissue was obtained by water quenching after solid solution in the single phase region of Ti-55531 alloy.The strain rate was 0.0005s-1 and 0.1s-1.The mainl deformation mechanism in the process of compression deformation at room temperature was slip.When the engineering strain was 8%-10%,the deformation mechanism is dislocation slip.We found the strain induced ?"martensite transformation and torsional deformation when the engineering strain was 30%.The shear band appeared when the engineering strain increased to 60%at the strain rate of 10s-1.There were primary alpha phase and residual beta phase after solid solution treatment in two phase region.The strain rate was 0.0005s-1.The dislocation was mainly concentrated in the primary alpha phase when the engineering strain is from 8%to 10%.When the engineering strain increases to 20%,the primary phase and residual phase of the beta phase boundary generated dislocation pile-up.When the engineering strain increased to 60%,a large number of dislocation cells were found in the deformable tissue at the strain rate of 10s-1 The structure obtained after solid solution and aging treatment in two phase region was primary alpha phase,secondary alpha and residual beta phase.The strain rate was 0.0005s-1.The deformation was mainly concentrated in the primary alpha phase when the engineering strain is 8%.When the engineering strain increases to 10%,dislocation tangles occurred in the primary alpha phase.When the engineering strain increases to 15%,dislocation tangles occurred in the secondary alpha phase.The dislocation density in the residual beta phase increased gradually.Local had also undergone a dislocation pile-up and dislocation tangles.Eventually,they participate in the co-ordination of plastic deformation.