Composition Design And Microstructure And Properties Of New High Strength And Toughness Titanium Alloy

?titanium alloy has good application prospects in aerospace vehicle structural parts for which exhibits high specific strength,cold formability and corrosion resistance.However,the strength and toughness of titanium alloy structures need to be further strengthened with the rapid development of China's aerospace industry.Therefore,it is necessary to develop new high strength and toughness titanium alloy.In this thesis,three?titanium alloys were designed according to alloy design criteria,empirical parameters and electronic parameters,named Ti-V-Mo-Cr-Fe-Al(1#),Ti-V-Mo-Cr-Zr-Al(2#)and Ti-Mo-Al-O(3#).The molybdenum equivalents of the three alloys were 13.60,14.16 and 15.00 respectively and the deformation mechanism of the alloy was predicted by calculating(B_o,M_d)values.in addition,the density,phase transition point,theoretical strength of?phase and volume fraction of?phase in the annealed alloy structure were predicted by theoretical calculation.Optical microscope(OM),scanning electron microscope(SEM)and X-ray diffraction(XRD)were used to observe and analyze the microstructure of the samples under different heat treatment processes and the corresponding compressive properties were measured.The results exhibited that the phase transition points of the three alloys were 840 ~oC,790 ~oC,900~oC,respectively,and the difference between the calculated phase transition points(822 ~oC,768 ~oC,905 ~oC)was within the experimental error range.1#and 2#alloys showed the best compressive properties when aged at 580~oC for 6 hours.Moreover,aging at 550~oC for more than 8 hours had a tendency to obtain better properties.3#alloy showed better compression properties and compressive strength reached 1800 MPa after aging at 500 ~oC for 2 hours.Cold rolling of the samples with different reduction and heat treatment of the rolled samples with different processes were carried out.The results exhibited that the three alloys showed more twins and 1#alloy exhibited phase transformation during rolling,which was the same as that predicted by(B_o,M_d)values.After double-stage cold rolling and annealing,1#alloy showed better plasticity,?=12%,at this time?_b=1120 MPa.2#alloy can be cold rolled with 85%reduction.After recrystallization annealing at 800~oC/30 min for 60%cold rolling reduction,the alloy showed good plasticity?=18%,at this time?_b=1200 MPa.After normalizing and aging at 550 ~oC/10 h,the tensile strength of the alloy reached 1510 MPa,at this time?=5%.3#alloy could be cold rolled with 85%reduction,annealed after rolling to obtain 15%elongation and aged after normalizing to obtain 1395 MPa tensile strength.