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Microstructure Evolution During Hot Deformation Of Near Beta Ti-5553 Alloy

Source: Cheng Jun. "Journal of Alloys and Compounds"

Near beta titanium alloys have been widely used in aerospace industry because of their high yield strength, excellent resistance to fatigue crack growth and good quenching performance.

For example, in the near beta titanium alloy in the most representative of the alloy, that is, Ti-1023 (nominal composition: Ti-10V-2Fe-3Al) alloy forging structure has been used to manufacture the aircraft landing gear of the Boeing 777. 

Similarly, the Ti-5553 (nominal composition: Fe Ti-5Al-5Mo-5V-3Cr-0.5) alloy forgings have also been used to make the landing gear of the Boeing 787 and the Airbus 350 aircraft. In general, the mechanical properties of titanium alloys depend largely on the volume fraction, morphology and distribution of the phase. For example, in titanium alloys with more spherical alpha phase is conducive to improve the plasticity, and has a more lamellar alpha phase is conducive to improve the fracture toughness.

 Moreover, the microstructure and mechanical properties of the near - beta titanium alloy are very sensitive to the thermal deformation process parameters. For this research, the flow stress curve characteristics and microstructure evolution behavior of titanium alloy during hot deformation are mainly focused on, and few people pay attention to the behavior of strain induced phase transformation.

Hua Ke and others used Gleeble3500 thermal simulation test machine to study the thermal deformation behavior of near beta Ti-5553 alloy under the condition of deformation temperature 750 ~ 900 degrees C and deformation rate of 0.001 ~ 1 s-1. The influence of different thermal deformation conditions on Microstructure and deformation mechanism was studied by TEM and EBSD. The results show that the dynamic recovery and dynamic recrystallization microstructure evolution of Ti-5553 alloy under this hot deformation condition will occur, and the phase and the phase of the alpha phase are not strictly followed by Burgers. Of 

ti-5553 alloy in hot deformation appearing in the alpha - layer structure of organization evolution process can be beta phase wedge model to explain, which in the lamellar spheroidization process will move in and out of the internal atomic beta opposite lamellar alpha phase diffusion phenomena appear. The change of machining parameters can significantly improve the power of phase transition. The phase transition process of deformation induced beta alpha is mainly caused by the defects of microstructure (deformation bands and dislocations).

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