| The new?-Ti alloy has excellent specific strength,good toughness and fatigue resistance,and is widely used in aerospace,biomedicine and automotive industries.Cold-rolled high-strength?-titanium alloy sheet is the main application route,and the cold-rolling process and subsequent heat treatment have significant effects on the structure and properties of the?-titanium alloy.The cold rolling and subsequent solution treatment of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe high-strength?titanium alloy showed that:at a large degree of cold deformation,the?grains deformed due to uneven deformation,for belts and elongated grains,in the short-term solution process,static recrystallization occurs preferentially in the unevenly deformed places(deformed belts and elongated grain boundaries).The main recrystallization method in the deformed belts is grain boundary annex,the abnormal growth of nucleation and sub-crystals;the main recrystallization methods at the elongated grain boundaries are the prominent nucleation of grain boundaries and the nucleation of poor orientation gradients.With the increase of the solution time,the non-recrystallized areas begin to nucleate,and the preferentially recrystallized areas begin to grow,and the average grain size increases at a slower rate.As the annealing temperature increases,the recrystallization rate increases,the time required to complete the same recrystallization volume fraction decreases,and the increase rate of the average crystal grain size increases.Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy forms a strong deformation texture after cold rolling,forming?-fiber:{111}<110>and?-fiber:{111}<112>;And after annealing at 820?for 5 minutes,complete recrystallization occurs,the texture is significantly weakened,and only a weak{001}<110>?-fiber texture is formed.The research on the precipitation of variants shows that:during the aging precipitation process,the Burgers orientation relationship between?phase and?phase,namely(0001)?//{110}?and<11-20>?//<111>?;after high-temperature forging,small secondary?phases are precipitated in the?grain boundaries and within the grains;in the deformation zone of the?grains after cold rolling,long needle-like secondary?phases along the direction of the elongated deformation zone are precipitated.Fine needle-like secondary?phases are precipitated outside the deformation zone.When the degree of recrystallization is low,a large number of small secondary?phases are precipitated in the numerous unrecrystallized regions,and a small amount of secondary?phases are precipitated in the recrystallized grains;when the degree of recrystallization is higher,there are many recrystallized regions.,The secondary?phase is preferentially precipitated at the grain boundary,and parallel to each other,a small amount of precipitation in the crystal,agglomerated together.The higher the degree of recrystallization,the easier it is to form the?-fiber texture of{001}<110>,and the greater the probability of variant selection during the???transition,the easier it is to precipitate{0001}?parallel to the common{110}?plane.The secondary?phase transformation of the?plane.Research on the heat treatment system of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy shows that when the solution time is 5min,the grains are fine and uniformly distributed,the strength of the alloy is 843Mpa,and the elongation is 9.2%.Has high strength and plasticity.A large number of equiaxed dimples can be seen from the tensile fracture,indicating that the alloy is mainly ductile fracture,and the fracture mode is mainly microporous aggregate fracture,which has good plasticity.Subsequent aging treatment will precipitate needle-like secondary?phases during aging,which can further increase the strength of the alloy.As the aging temperature increases,the strength of the alloy decreases from 1392MPa to 1134MPa,and the plasticity increases from%0.78 to 7.8%.Direct aging of the cold-rolled alloy results in the precipitation of smaller secondary?phases.As the aging temperature increases,the strength of the alloy decreases from 1456MPa to 1181MPa,and the ductility increases from0.35%to 1.56%.When the Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5F alloy undergoes work hardening at the early stage of high temperature deformation,the flow stress reaches its peak.As the strain increases,flow softening occurs,and the flow stress of the alloy begins to decrease continuously.Under the same strain rate(8.33×10-4s-1,5.00×10-3s-1,1.00×10-2s-1),as the deformation temperature of the alloy increases(700?-800?),when the alloy deforms,the flow stress is reduced.When the deformation temperature is the same,as the strain rate increases(8.33×10-4s-1-1.00×10-2s-1),the flow stress of the alloy increases continuously. |
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