Microstructure, texture and hardness of a metastable β-titanium alloy after bar-rolling and annealing


Microstructure, texture and hardness of a metastable β-titanium alloy after bar-rolling and annealing

Gu, B.; Chekhonin, P.; Schaarschuch, R.; Oertel, C.-G.; Xin, S. W.; Ma, C. L.; Zhou, L.; Gan, W. M.; Skrotzki, W.

The microstructure and texture evolution of a metastable Ti-5Al-3V-3Mo-2Cr-2Zr-1Nb-1Fe alloy during bar-rolling and after various thermal treatments was investigated by high-energy synchrotron diffraction and electron backscatter diffraction. Bar-rolling is applied in the (α+β)-phase field in order to achieve a bi-modal (duplex) microstructure. The effect of dynamic recrystallized and recovered zones on texture of Ti5321was analyzed separately, as well as the texture of primary α-precipitates and secondary α-lamellae. The texture of the recovered zones is characterized by a cube component ({001}<100>) plus α- and γ-fibre with dominant {100}<110>, {112}<110>, {111}<110> components, while the texture of the recrystallized zones is a strong cube texture. After aging or recrystallization plus aging, this texture component remains, while it disappears after solution treatment. The primary α-precipitates have their c-axes perpendicular to the rolling direction and do not follow the Burgers orientation relationship. This texture characteristics remains after various thermal heat treatments. Secondary α-lamellae obey the Burgers orientation relationship. Moreover, a variant selection of secondary α-lamellae occurs. The mechanism of texture formation of the β-phase and the precipitation behavior of the α-phase is discussed.
The hardness increase can be attributed to size, shape and volume fraction of the α-precipitates.
Different combinations of primary α- and secondary α-precipitates make an increase in hardness of about 11%.

Keywords: Metastable β-titanium alloy; Bar-rolling; Microstructure; Texture; Microhardness

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Publ.-Id: 30724