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Deformation and phase transformation are two major topics in the study of titanium alloy materials. Titanium alloys usually require a series of complex thermo-mechanical treatments to obtain a microstructure corresponding to service performance. Its hot deformation behavior is a typical thermo-mechanical coupling process. Deformation and phase transformation may occur simultaneously and affect each other. It is one of the current research hotspots. However, due to the inevitable existence of dynamic recovery / recrystallization, microstructure fragmentation / spheroidization, a large number of deformation defects, deformation texture, and stress-induced phase transformation during hot deformation, coupled with the changes of the phase transformation kinetics characteristics and the crystallographic mechanism of the variant selection under thermo-mechanical coupling, directly leads to the extremely complicated dynamic phase transformation behavior of the titanium alloy during the hot deformation process, and it becomes quite difficult to reveal its evolution law in depth. This paper summarizes the main characteristics and laws of titanium alloy deformation and phase transformation in view of the dynamic phase transformation behavior of titanium alloy during hot deformation,mainly introduces the research progress of the dynamic phase transformation of the titanium alloy under the thermo-mechanical coupling from the three aspects of precipitation phase morphology characteristics, variant selection mechanism and phase transformation kinetics characteristics, and summarizes and prospects its research and development trend.

As Ti-70 is a new type of marine titanium alloy, research on the recrystallization process of its sheet is necessary. This article studies the effects of different temperatures and times of annealing on the recrystallization process of 5.0 mm thick Ti-70 titanium alloy cold-rolled sheets by metallographic analyses and hardness tests. The results show that after 30 min of annealing at 620~700 °C, the recrystallization process was mostly complete, and uniform and equiaxed recrystallized grains could be obtained. The recrystallization process starts after 8 min of annealing at 700 °C, and after holding for 15~30 min, the recrystallization process is almost complete and the grain size is about 8.2 μm. The recrystallization activation energy of a Ti-70 titanium alloy cold-rolled sheet is Qr = 11.0645 × 104 J/mol. The ultimate tensile strength (Rm) can be controlled between 705 and 852 MPa, the yield strength (Rp0.2) can be controlled between approximately 623 and 793 MPa, and the elongation percentage (A) can be controlled between approximately 10.0 and 25.0% after rolling and heat treatment of Ti-70 alloy sheets. [ABSTRACT FROM AUTHOR]

In this study, an approach utilizing a conjunction of the extended finite element method (XFEM) and the Gurson‐Tvergaard‐Needleman (GTN) micromechanical damage model is proposed for predicting the ductile crack propagation of a mill‐annealed Ti‐6Al‐4V alloy. The cohesive model‐based XFEM approach is used to capture the continuous crack propagation process, and the GTN model is applied to describe the constitutive behaviour of the material. Simulations are conducted by using the standard finite element code ABAQUS following a Newton–Raphson algorithm solution with employing the user material subroutine of the GTN model. In comparison with the experimentalresults of the smooth, notched and cracked titanium specimens, this approach is shown to be an efficient method for simulating the ductile crack propagation process under different stress triaxialities. [ABSTRACT FROM AUTHOR]