The Effect Of Microstructure And Properties Of Ti-1300 Alloy At Severe Plastic Deformation And Heat Treatment

The microstructure and mechanical properties of Ti-1300 alloy processed by solution treatment and ECAP deformation and following aging heat treatment were studied by advanced technology methods,such as optical microscope(OM),scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM),X-ray diffractometry(XRD)and mechanical properties testing at room temperature.The main research conclusions of this research are as follows.The grains of Ti-1300 alloy deformed by ECAP are not broken.The grain boundaries are clear and distinct.A large number of mixed dislocations of positive and negative edge dislocations and screw dislocations appear in the grain boundaries after deformation,which increases the difficulty of dislocations slip.In addition,there are lots of shear slip bands in deformed grains.And after the two-pass deformation,the more intertwined shear slip bands in grains,the clearer and flatter the slat interfaces with larger dislocation density,whose average width is 50nm.The 900°C solution treated Ti-1300 alloy shows the{332}<113>nano-twin structure after ECAP two-pass deformation,and the width of twin structure is approximately 70 nm.And with the deformation increasing,the original(110)[11?1]texture of Ti-1300alloy after ECAP deformation gradually changed toαtexture,and D texture and cubic texture were formed.What’s more,all of the microstructures are almost transformed into substructures after first deformation.While the substructures decrease after the two-pass deformation,the deformed grains and the low angle grain boundaries gradually increase.The results of aging heat treatment for Ti-1300 alloy in different states display that in the two-phase region ofα+β,a part ofα_p phase is retained and a part ofα_s phase is precipitated at the same time;after solution and aging treatment in the single phase region ofβ,α_s phase is precipitated on the wholeβmatrix.The content ofα_s phase increases with aging time,and the hardness of Ti-1300 alloy grows up rapidly and then following stable state by degrees.The microstructure of pre-deformed Ti-1300 alloy produces numerous slip lines and defects,which increase the distortion energy,so that it provides an important condition for theα_s phase nucleation,growth,and precipitation.Therefore,the rate and content of precipitation of the pre-deformedα_s phase are increased at the same aging heat treatment,so the micro-hardness are.