This study is an experimental investigation on the tensile responses of Ti–5Al–2.5Sn alloy over a wide range of strain rates. Uniaxial tension tests within the rate range of 10⁻³–10¹ s⁻¹ are performed using a hydraulic driven MTS810 machine and a moderate strain-rate testing system. The high-rate uniaxial tension and tension recovery tests are conducted using a split-Hopkinson tension bar to obtain the adiabatic and isothermal stress–strain responses of the alloy under dynamic loading conditions. The experimental results show that the value of the initial yield stress increases with the increasing strain rate, while the strain rate sensitivity is greater at high strain rates. The isothermal strain-hardening behavior changes little with the strain rate, and the adiabatic temperature rise is the main reason for the reduction of the strain-hardening rate during high strain-rate tension. The electron backscatter diffraction (EBSD) analysis of the post-deformed samples indicates that there are deformation twins under quasi-static and high-rate tensile loadings. Scanning electron microscope (SEM) micrographs of the fracture surfaces of the post-deformed samples show dimple-like features. The Zerilli–Armstrong model is modified to incorporate the thermal-softening effect of the adiabatic temperature rise at high strain rates and describe the tension responses of Ti–5Al–2.5Sn alloy over strain rates from quasi-static to 1050 s⁻¹.

The complex deformation usually involves wide strain-rate change. However, few efforts have been devoted to investigate the effect of strain rate history on the tensile behavior of α + β titanium alloy. In present paper, tensile tests of Ti-6.6Al-3.3Mo-1.8Zr-0.29Si alloy were carried out under both constant and variable strain-rate conditions within the region from 10⁻³~500 s⁻¹. A single stress pulse experimental technique was utilized to conduct the recovery tests. The strain-rate history effect was examined. It is found that the flow stress is independent on the strain rate history, though the alloy exhibits obvious positive strain rate sensitivity. The Taylor-Quinney coefficient of the plastic work converted to heat is proved as 0.9 at high strain rates. The cavitation fracture mechanism is revealed by microstructural observation over the full range explored. In basis of the experimental results and other pulished literatures, empirical Khan-Huang-Liang constitutive model was suitably modified to account for the strain-rate dependent behavior. Good agreement is achieved between the modeling prediction results and experimental data.

The effects of aging treatment and the volume fraction of precipitation particles on the nano-hardness and nano-indentation morphology of Ni-based single crystal superalloys are systematically investigated. Using nano-indentation tests and atomic force microscopy (AFM), this study examined the mechanical properties and related physical mechanisms of Ni-based superalloys that have two volume fractions of precipitation particles and four aging treatment times. Results analyzed using the Oliver–Pharr method indicate that prolonging the aging time or increasing the volume fraction of particles enhances the nano-hardness and creep resistance of Ni-based single crystal superalloys and reduces the indentation-affected area. Additionally, the nano-hardness and elastic modulus decrease gradually with increasing applied force, revealing an obvious indentation size effect. These variations are closely linked to the size and density of particles and work hardening rate, as well as to the topologically close-packed (TCP) phases, which influence dislocation movement and accumulation within the material and lead to various nano-indentation behavior in Ni-based single crystal superalloys. The related study provides theoretical guidance and experimental data to support the design and application of superalloys.