| Along with development of aviation and spacelight,titanium alloys are expected as good matching of strength,plastic and toughness.Ti62A alloy is one of the titanium alloy of damage tolerance which remains with Ti-Al-Mo-Sn-Zr-Cr-V-Si-Fe series.The alloy has excellent strength and toughness,which has been applied in the field of aviation and ocean engineering.In order to obtain the excellent mechanical properties with a combination of high strength,high ductile and high modulus,an(?+?)two phases Titanium alloy Ti-5.92Al-3Mo-1.45Cr-2.25Sn-2.15Zr-1V-0.17Fe-0.08Si(wt%)was designed.This paper studied microstructure evolution and precipitation behavior of precipitation phase in the different heat treatments.This paper also studied the effect of the microstructrue on mechanical properties at room temperature.At the same time,the cooling process of the welded sample was simulated by the end quenching experiment.The phase composition and mechanical behavior of the sample under the continuous cooling gradient were studied.After heat treatment in the two phase region,the samples were cooled by three different cooling methods in the experiment.And then we used different temperature of aging heat treatment.The results of the experiment show that the alloy produced ?" phase after oil quenching or water quenching.As the aging temperature increases,the size of the secondary phase in the alloy is gradually coarsening,and the XRD and SEM results show that the volume fraction of the secondary phase is small.When the aging temperature is more than 860,the beta matrix will release a very fine secondary phase.The effect of precipitation phase on the mechanical properties was studied by tensile test and fracture toughness test.The results indicate that the tensile strength of the samples of three kinds of cooling ways after solution treatment tend to decrease firstly and then increase due to the change of the size of the secondary alpha phase with increasing aging temperature.The tensile strength and yield strength of water quenched or oil quenched samples were both larger than that of air cooled under the same aging temperature.At the same aging temperature,the fracture toughness of the samples after air cooling is larger than that of the water quenched or oil quenched samples.Fracture toughness of the samples after air cooling was jointly affected by intermetallic compounds of Ti3Al and content and morphology of secondary ? plates.The coarsening of the secondary a lamellae can improve the toughness,while the ?2 particles can significantly reduce the toughness of the material while increasing the strength of the material.Therefore,with the increase of aging temperature,KIC has a "V"shaped trend,that is,the first decrease and then increase.Under the condition of oil quenching or water quenching,The size of secondary alpha phase has significant influence on the mechanical properties of the alloy.With the increase of aging temperature,the fracture toughness of the alloy increased.Microstructure and mechanical properties of the two-phase titanium alloy Ti62A,after the heat treatment based on soaking this alloy in the P range,cooling by ending quench and aging at a wide range of temperature,were investigated in this experiment.The microstructure and phase composition of the alloy were characterized by SEM and XRD,and the mechanical properties were analyzed by means of hardness test.With the distance from quenching end increases,the cooling rate decreased,so the content of ?" decreased until no longer produce,and? and ?phase precipitate and grow.With the increase of the distance from the quenching end,the axial hardness of the end quenching sample first increased and then decreased.The hardness of samples along the central axis after aging at different temperature increases first and then decreases.As the aging temperature increases,the hardness of the same position on the axial line of the quenched sample is decreased continuously. |
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