Ti-Mo-Nb-Cr-Al-Fe-Si alloy is a new metastable β titanium alloy with excellent combination of strength and ductility. The β grain-growth exponent and the activation energies for β grain growth for the investigated alloy at specified temperature were computed by the kinetic equations and the Arrhenius-type equation. The rate of β grain growth decreases with elongating solution treated time and increases with the increasing solution-treated temperature. The β grain-growth exponents, n, are 0.461, 0.464 and 0.469 at 1113, 1133 and 1153K, respectively. The β grain growth activation energy is determined to be 274 KJ/mol.

The hot deformation behavior of Ti-4.5Al-3V-2Mo-2Fe (SP-700) titanium alloy in the temperature range of 650°C~950°C and constant strain rate of 0.01, 0.1, 1 and 10s-1 has been investigated by hot compressive testing on the Gleeble-1500D thermal simulation test machine. The experimental results indicated that the hot deformation behavior of SP-700 alloy was sensitive to the deformation temperature and strain rate. The peak flow stress decreased with the increase of temperature and the decrease of strain rate. The flow curves characteristic under different deformation parameters show significant different. Analysis of the flow stress dependence on strain rate and temperature gives a stress exponent of n as 4.8235 and a deformation activation energy of Q as 410kJ/mol. Based on the dynamic materials model, the processing map is generated, which shows that the most peak efficiency domain appears at the temperature of 725°C~775°C and the strain rate of 0.001 s-1~0.003s-1 with a peak efficiency of 45% at about 750°C/0.01s-1.

Hot compressive experiments of TC4-DT titanium alloy were performed on Gleeble 3500 hot simulator. The influence of hot deformation parameters on high temperature deformation behaviors were investigated, including deformation temperature (938°C~1038°C), deformation degree and strain rate (0.01s-1~10s-1). The results indicated that the peak (σp) and steady-state flow stress (σs) of TC4-DT alloy decreased with the increase of deformation temperature under the same strain rate, especially under a high strain rate. The flow stress increased sharply then decreased and kept invariant finally with the increase of deformation degree. The flow stress increased with the strain rate increasing and exhibited different characteristics in different strain rate range. The optimum conditions obtained based on this investigation of TC4-DT alloy as follows: temperature was 938°C~1008°C, stain rate was 0.01s-1~0.1s-1.

The hot deformation behavior of Ti-Al-Nb-Zr-Mo-Cr titanium alloy was studied by hot compressive method in this paper, and the flow stress constitutive equation and activation energy also calculated. The results show that the flow stress increased with deformation temperature dropping and strain rate increasing. The flow behavior of the sample hot-deformaed exhibited a peak value of stress in the α+β field, whereas, the true stress attained a steady state in the β field. According to the stress-strain curves of the alloy and its stress characteristics, the Arrhenius constitutive equation was obtained. The average activation energy was about 654.228 KJ/mol in the α+β field, and about 272.196 KJ/mol in the β field, respectively.

This article investigated the fatigue crack growth behaviors in the novel TC32 titanium alloy with bimodal and basket-weave microstructures, which were respectively obtained by the convectional (α+β) phase forging and quasi-β forging processing. Results showed that at the same level of tensile performance, the basket-weave microstructure had a lower fatigue crack growth rate than the bimodal microstructure, as the basket-weave microstructure had a more tortuous crack path, a rougher fracture surface and more secondary cracks. All these served to improve the fatigue crack growth resistance, which attributed largely to the effects of crack closure. Moreover, secondary cracks grew primarily along the α/β interfaces for the basket-weave microstructure but directly went across the colony-type lamellar (α+β) phase and the primary α phase without obvious regularity for the bimodal microstructure.