Study Of Influences Of ω Phase Transformation On Microstructures And Properties Of Titanium Alloy

As a kind of important metal materials, titanium alloys developed in the1950s have beenused in many fields because of high specific strength, good corrosion resistance and high heatresistance. Therefore, it is important and valuable in theoretical research and practicalapplication to study the influences of ω phase transformation on the microstructures andproperties of titanium alloys.In this paper, the influences of athermal omega phase and isothermal omega phase on themicrostructures and properties as well as the influences of V and Al elements on themicrostructures and properties were studied by using vacuum consumable electric arc furnace,heat treatment furnace, scanning electron microscope, and XRD diffraction. The studiedresults are as follows.（1） In Ti-Fe binary alloy, the content of4%⁶%Fe can satisfy the formation condition ofathermal omega phase, i.e., G_β-G_α <G_{barrier α},and G_β-G_ω> G_barrierω.The solution temperaturecan significantly affect the diffusion behavior of elements stabilizing β phase, and resut in thevariation in the stability of β phase. As a result, the formation condition in component forathermal omega phase can also be changed.（2） In Ti-Fe binary alloy, isothermal omega phase can be formed when the athermalomega is decomposed. With the increase in ageing temperature, the omega phase isdecomposed quickly; the omega phase may be decomposed into α phase and the omega phasecontaining more β stabilizer, then metastable β and α phases are formed; finally theequilibrium α and β phases are formed.（3） In Ti-Fe binary alloy, isothermal omega phase can be precipitationed easily whileaged at low temperature. But the higher ageing temperature is not help for the precipitation ofisothermal omega phase. The influences of alloying concentration on isothermal omega phaseare not invariable, that is isothermal omega phase can be formed once the formation conditionin component of isothermal omega phase can be satisfied.（4） In Ti-Fe binary alloy, the isothermal omega transformation is related to diffusion anddisplacement, diffusion can supply the component condition for displacement; whileisothermal omega phase can be formed by means of displacement once the componentcondition is satisfied. Therefore, the model for isothermal omega phase should be “diffusion-displacement-diffusion-dispalcement·····”, and these alternant transformations can be carriedout until the equilibrium α+β microstructures can be formed.（5） The variation tendency in hardness for Ti-V binary alloy is similar to the one of Ti-Febinary alloy; in addition, the addition of Al element can cause the significant decrease inhardness of Ti-Fe alloy.