Study On Hot Deformation Mechanism Of Ti-1023 Alloy

Near?titanium alloy has the advantages of high specific strength,good corrosion resistance,and good biocompatibility.It is widely used in aerospace,chemical,medical and other fields.This paper takes Ti-1023 alloy as the research object,and uses various characterization methods to evaluate the stress-strain behavior,dynamic recovery/dynamic recrystallization(DRV/DRX),phase transformation characteristics and spheroidization of the lamellar?phase during thermal compression deformation in high and low temperature regions,as well as the phase transformation characteristics under heat treatment and room pre-deformation aging have been studied in depth.When Ti-1023 alloy is compressed at high temperature at 750?(?+?phase region),DRV/DRX will occur,and the?phase will be precipitated by dynamic nucleation.When the strain rate is 0.0005 s^-1,0.001 s^-1,and 0.01 s^-1,the peak stresses of the alloy are 37MPa,57 MPa,and 106 MPa,respectively,and the critical stresses for DRX are 35.7 MPa,53.2 MPa,and 100.2 MPa,respectively.When the alloy is compressed at 750?,the original?grains are flattened and a large number of small-angle grain boundaries are formed.The?phase is preferentially precipitated at?and small-angle grain boundaries,and the?/?orientation relationship is deviates greatly from the Burgers orientation relationship,the Pitsch-Schrader orientation and the Potter orientation relationship.After pre-deformation at room temperature,a large amount of martensite is produced in Ti-1023 alloy.After high temperature(750?)aging treatment,the?phase is preferentially precipitated in spherical and short rod shapes at the interface of primary martensite and secondary martensite.With the extension of the aging time,the spherical and short rod-shaped?phases merged and grew.When the aging time is 40 min,the?and?phases at the martensite interface do not follow the Burgers orientation relationship,while the?and?phases outside the martensite all follow the Burgers orientation relationship.When the aging time is extended to 60 min,the?phase at the martensite interface and the?phase in other regions follow the Burgers orientation relationship with the?phase.Ti-1023 alloy exhibits DRV and DRX during low temperature(550?)thermal compression deformation,and a large number of?phases with various morphologies are precipitated.When the strain rate is 0.0005 s^-1,0.001 s^-1,and 0.01 s^-1,the peak stresses are 423 MPa,496 MPa,and 797 MPa,respectively;the critical stresses for DRX are 339.5MPa,427.1 MPa,and 728.7 MPa,respectively.The?phase precipitated when the alloy is compressed at low temperature exists in the form of equiaxed?,lamellar?,and a small amount of broken?phase.In the interior of the slip band,the?phase is densely precipitated in an equiaxed shape,and the area outside the slip band is precipitated in a lamellar shape.A small amount of the lamellar?phase is broken.The?phase preferentially precipitates small short rod-like?phases in the primary martensite and the secondary martensite of the Ti-1023 alloy after pre-deformation and subjected to a long-term aging treatment at low-temperature(550?).Compared with pre-deformed high-temperature aging,the precipitation of?phase is more difficult during low-temperature aging,and the size is smaller.The precipitation of?phase is inhibited during high temperature compression of Ti-1023 alloy.The low temperature compression promoted the precipitation of?phase.There is an equilibrium point between?phase transformation and DRV/DRX.The hot deformation mechanism of Ti-1023 alloy is mainly the dislocation migration mechanism.In addition to the dislocation migration mechanism,the grain boundary diffusion mechanism and grain boundary sliding mechanism also exist in the hot deformation process of the alloy,which are related to the lamellar?phase fragmentation and spheroidization.The three mechanisms work together and promote each other to promote the plastic deformation of the alloy.