Composition Design And Research On Microstructure And Properties Of Multi-component ? Titanium Alloys

In this paper,three ?-type titanium alloys of Ti-5V-4Mo-3Cr-3Zr-3Al(1#alloy),Ti-4V-6Mo-3Cr-3Zr-3Al(2#alloy)and Ti-5V-7.5 Mo-3Cr-3Zr-3Al(3#alloy)were designed by the design criteria of alloy composition combined with molybdenum equivalent[Mo]eq,K? stability coefficient,valence electron concentration e/a,(Bo,Md)and other parameters.The Kp stability coefficients of the three alloys were 1.16,1.30 and 1.65,respectively.Molybdenum equivalent[Mo]eq were 9.25,10.48,14.25.The theoretical ?/? phase transition points were 810?,786? and 741?,respectively.The volume fractions of a phase in annealed alloy were 55.45%,51.24%and 36.96%,respectively.(Bo,Md)were(2.7807,2.3766),(2.7883,2.3765)and(2.7854,2.3572),respectively.It is predicted that twins will occur during the deformation of the three alloys,and martensite transition may take place in the 1#alloy and 2#alloy,while martensite transition will not take place in the 3#alloy.Optical microscope(OM),scanning electron microscope(SEM)and X-ray diffractometer(XRD)were used to observe and analyze the microstructure of the samples in the as-cast state and under different processess of solid solution treatment and aging treatment,and the compression test was carried out by RG3050 universal testing machine.The cold rolling deformation and post-rolling heat treatment of three kinds of alloy samples with different deformations were carried out,and the tensile mechanical properties were tested.The experimental results show that the actual ?/? phase transition points of the three alloys were 830?,810? and 770?,respectively,which are not different from the theoretical calculation values,indicating that the theoretical calculation has certain guiding significance.Among the three experimental alloys,the effect of precipitated a phase of 1#alloy was stronger,while that of 3#alloy was weaker.1#alloy has the best compressive mechanical properties at 520?/2h,with the compressive strength up to 1800MPa;2#alloy and 3#alloy have the best compressive mechanical properties at 520?/5h,with the compressive strength above 1500MPa and 1700MPa,respectively.Twins were produced in all the three alloys during the deformation,and martensite transformation occurred in both the 1#alloy and 2#alloy,which was consistent with the theoretical prediction.1#alloy after two times of 50%cold rolling+annealing,then aging treatment,the tensile strength?b=1360MPa,?=5.8%.2#alloy after 72%cold rolling+annealing,then aging treatment,the tensile strength ?b=1313MPa,?=6%.3#alloy after 75%cold rolling+annealing,?=23%,the tensile strength ?b=1260MPa,?=7.5%.