Research On The Rolling Process And Mechanical Properties Of Ti-Mo-V-Al-Fe Alloy

The metastable beta titanium alloy has been widely used as an important development direction of high-strength lightweight metal structure materials for aerospace due to its high specific strength and good matching of strength and ductility,and it is one of the most ideal candidate materials for load bearing structure with weight reduction.In this dissertation,with high strength titanium alloy as the research subject,a new type of metastable beta titanium alloy has been designed.The effect of hot rolling and heat treatment on microstructure and tensile properties of the metastable titanium alloys was analyzed by optical microscope,X-ray diffraction analysis methods,scanning electron microscope,transmission electron microscope and tensile testing machine.The main contents and the conclusions of the research are as follows:A new type of Ti-6Mo-5V-3Al-2Fe alloy was designed based on the principle of alloying,molybdenum equivalent and D-electron theory,under a twice melting process with vacuum consumable electrode smelting technology,where the chemical composition of the casting alloys was in accordance with the theoretical design composition.The phase transformation point of the alloy is 810?which was measured by the method of calculation and differential thermal analysis.The alloy was hot-rolled at three different temperatures,and the deformed?grains were elongated along the deformation direction and a certain amount of primary?phase were precipitated after hot rolling below the phase transformation point?800??.When the hot-rolled temperature was 850?,the microstructure turned into small equiaxed?grains,and when the hot rolling temperature increased to 900?,the dynamic recrystallization had completely occurred,and the isometric?-grains were coarsening.Compared with the other two states,850?hot-rolled state alloy has the most excellent strength and plastic.The precipitation of the secondary phase which through different solution plus aging treatment has a great effect on the alloy,the strength of the alloy has been greatly enhanced with the secondary?phase.When the alloy was 450?,the?phase was formed in the microstructure,the strength of the alloy increased,but the elongation decreased significantly.the secondary?phase was formed in the microstructure and the strength of the alloy was further increased at 500?,meanwhile the?phase of the alloys were decreased,and the ductility of the alloy was increased.while the 550?-600?aging occurs,the size and spacing of the secondary increased and the enhancement effect was significantly reduced.The tensile properties of all the different aging treatments had been analyzed,it can be seen that the effect of aging temperature on the tensile properties of the alloy is great,meanwhile the effect of aging time on the tensile properties of the alloy is relatively small.The alloy has good strength under the condition of 500?,and has good plasticity under the condition of 600?.The alloy has the most optimal strong plastic matching at the aging treatment of 500?/4h,at which its tensile strength is R_m=1426.52MPa,yielding strength is R_p0.2=1311.34MPa,and the elongation at the rear is A=8.0%.