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Material characterization at moderate strain rates is an important factor for improving the adequacy and accuracy of analysis of structures operating under extreme conditions. In this paper, the deformation and fracture of Ti-5Al-2.5Sn alloys were studied utilizing the punch test at strain rates up to several hundred per second. Loading velocities from 0.0003 to 15 m/s were realized during the spherical body penetration through a thin titanium plate. To describe the plastic flow and fracture of the Ti-5Al-2.5Sn alloy at strain rates ranging from 0.001 to 103 s−1, a micromechanical damage model was coupled with a viscoplastic constitutive model based on the dislocation dynamics. Numerical simulations of the punch test at 15 and 2 m/s were carried out to validate used constitutive relations. It was verified that the simulated fracture shape and deflections were similar to experimental ones. It was found that dynamic punch test is suitable for validation of damage kinetics under complex stress states.

A comprehensive study was performed of the deformation and temperature behavior during quasi-static tension, as well as the peculiarities of accumulation and dissipation of energy during plastic deformation. Microstructural analysis at the pre-fracture stage of pure titanium and Ti-45Nb alloy in the coarse grain (CG) and ultrafine-grained (UFG) states was also conducted. It was shown that substructural and dispersion hardening leads to a change in the regularities of dissipation and accumulation energies during deformation of the samples of the pure titanium and Ti-45Nb alloy in the UFG state. Some features of structural transformations during deformation of the pure titanium and Ti-45Nb alloy samples in the CG and UFG states were studied. A band and cellular-network and fragmented dislocation structure was formed in the case of the CG state, while large anisotropic fragments were formed in the UFG state, thus specifying a local softening of the material before fracture.

The microstructural investigation, mechanical properties, and accumulation and dissipation of energies of the magnesium alloy Mg-2.9Y-1.3Nd in the recrystallized state and after severe plastic deformation (SPD) by extrusion are presented. The use of SPD provides the formation of a bimodal structure consisting of grains with an average size 15 µm and of ultrafine-grained grains with sizes less than 1 µm and volume fractions up to 50%, as well as of the fine particles of the second Mg24Y5 phases. It is established that grain refinement during extrusion is accompanied by an increase of the yield strength, increase of the tensile strength by 1.5 times, and increase of the plasticity by 1.8 times, all of which are due to substructural hardening, redistribution of the phase composition, and texture formation. Using infrared thermography, it was revealed that before the destruction of Mg-2.9Y-1.3Nd in the recrystallized state, there is a sharp jump of temperature by 10 °C, and the strain hardening coefficient becomes negative and amounts to (−6) GPa. SPD leads to a redistribution of thermal energy over the sample during deformation, does not cause a sharp increase in temperature, and reduces the strain hardening coefficient by 2.5 times.

The paper presents the experimental results of the mechanical behavior of Ti-5Al-2.5Sn alloy at high strain rates and elevated temperature. Flat smooth and notched specimens with notch radii of 10 mm, 5 mm, and 2.5 mm were used. The experimental studies were carried out using the high-velocity servo hydraulic test machine Instron VHS 40/50-20. The samples were heated with flat ceramic infrared emitters on average between 60 s and 160 s. The temperature control in the working part of specimens was carried out in real time using a chromel-alumel thermocouple. The digital image correlation (DIC) method was employed to investigate the evolution of local fields in the gauge section of the specimen. Data on the influence of stress triaxiality on the ductility of Ti-5Al-2.5Sn alloy were obtained under tension with strain rates ranging from 0.1 to 103 s−1 at a temperature of 673 K. It was found that, at 673 K, the ductility of Ti-5Al-2.5Sn alloy increases with the increasing strain rate for both smooth and notched specimens.

This article investigated the mechanical behavior of Ti-6Al-4V alloy (VT6, an analog to Ti Grade 5) in the range of strain rates from 0.1 to 103 s−1. Tensile tests with various notch geometries were performed using the Instron VHS 40/50-20 servo hydraulic testing machine. The Digital Image Correlation (DIC) analysis was employed to investigate the local strain fields in the gauge section of the specimen. The Keyence VHX-600D digital microscope was used to characterize full-scale fracture surfaces in terms of fractal dimension. At high strain rates, the analysis of the local strain fields revealed the presence of stationary localized shear bands at the initial stages of strain hardening. The magnitude of plastic strain within the localization bands was significantly higher than those averaged over the gauge section. It was found that the ultimate strain to fracture in the zone of strain localization tended to increase with the strain rate. At the same time, the Ti-6Al-4V alloy demonstrated a tendency to embrittlement at high stress triaxialities.

The evolution of temperature fields and the deformation behavior of samples of VT1-0 titanium and zirconium Zr–1 wt % Nb alloys in coarse-grained and ultrafine-grained states is investigated under quasistatic stretching using infrared thermography. It is shown that the nature of the evolution of the temperature field in the process of deformation and the dependence of the maximum temperature on the strain in the working area differ for VT1-0 titanium and Zr–1 wt % Nb and depend on their structural and phase states, mechanical characteristics, and thermal diffusivity. It has been established that upon transition to the ultrafine-grained state, thermal diffusivity decreases by 6.5 and 9.3% for VT1-0 titanium and Zr–1 wt % Nb alloy, respectively. Differences in the deformation behavior of samples of VT1-0 titanium and Zr–1 wt % Nb alloy in the coarse-grained and ultrafine-grained states are associated with substructural hardening of the matrix phases of α-Ti and α-Zr and solid-solution hardening caused by the dissolution of β-Nb particles as the alloys under study are transferred into the ultrafine-grained state by severe plastic deformation.

This article presents the results of modeling the mechanical behavior of Zr–Nb and Ti–Nb alloys in a range of strain rates from 0.001 to 1000 1/s and temperature range 297–1273 K. A modification of constitutive equations describing the mechanical response of fine-grained and coarse-grained Zr–1Nb and Ti–13Nb–13Zr alloys in a wide temperature range is proposed. It was shown that the phase transition between the hexagonal closed packed and body-centered cubic crystal structure at elevated temperatures leads to a sharp change in strain rate sensitivity of the yield strength of Zr–Nb and Ti–Nb alloys. The proposed modifications of constitutive equations make it possible to describe the strain hardening and the strain rate sensitivity of the plastic flow stress over a wide temperature range in the coarse-crystalline and ultrafine-grained Zr–Nb and Ti–Nb alloys. The results can be used for engineering analysis of structural elements of technical systems and design of manufacturing technologies for biomedical products.

The present study investigates the effect of stress triaxiality on mechanical behavior and fracture of Ti-5Al-2.5Sn alloy in a practical relevant strain rate range from 0.1 to 1000 s&minus, 1. Tensile tests were carried out on flat smoothed and notched specimens using an Instron VHS 40/50-20 servo-hydraulic test machine. High-speed video registration was conducted by Phantom 711 Camera. Strain fields on the specimen gauge area were investigated by the digital image correlation method (DIC). The fracture surface relief was studied using digital microscope Keyence VHX-600D. Stress and strain fields during testing of the Ti-5Al-2.5Sn alloy were analyzed by the numerical simulation method. The evolution of strain fields at the investigated loading condition indicates that large plastic deformation occurs in localization bands. The alloy undergoes fracture governing by damage nucleation, growth, and coalescence in the localized plastic strain bands oriented along the maximum shear stresses. Results confirm that the fracture of near alpha titanium alloys has ductile behavior at strain rates from 0.1 to 1000 s&minus, 1, stress triaxiality parameter 0.33 &lt, &eta, &lt, 0.6, and temperature close to 295 K.

The paper analyzes the structure and mechanical properties of sheet-rolled Al 1560 alloy after four cycles of groove pressing. The analysis shows that under quasi-static uniaxial tension at a strain rate of 1 s-1, the offset yield strength of the groove-pressed alloy and its ultimate strength are respectively 1.4 and 1.5 times higher than their values in the as-received state. The ultimate tensile strain of the alloy after pressing is 17% against 21% in the as-received state, and its microhardness is 2.7 times higher. According to an electron backscatter diffraction analysis, the groove-pressed alloy has a bimodal structure composed of elongated coarse grains and agglomerates of equiaxed grains of micron and submicron sizes. When pressed, the alloy increases the density of its grain boundaries with a misorientation angle of less than 15° and changes its texture from rolling to upsetting whose volume during pressing grows. Part of the grain orientations in both states corresponds to recrystallization. The research data suggest that groove pressing provides grain structure refinement via plastic distortion in Al 15 60 alloy and a considerable increase in its strength properties.

A model for predicting mechanical properties of ultra-high temperature ceramics (UHTC) and composites within a wide temperature range is presented. A model can be useful for predicting the mechanical properties of UHTC composites under dynamic loading and thermal shock. Results of calculations taking into account the dependences nonlinearity of the normalized elastic moduli on homologous temperature T/Tm in the range of 0.2 - 0.62. are presented.. Residual stresses in ZrB2 composites reinforced with particles of refractory borides, carbides and nitrides after selective laser sintering (SLS) or spark plasma sintering (SPS) were predicted. It is shown that the fracture toughness KIC of UHTC increases at the sintering temperature in the range 0.45 – 0.62 T/Tm. The residual stress in the matrix of ceramic composites can differ on a sign due to difference between the thermal expansion coefficients of the matrix and inclusion phases. It is shown that the fracture toughness and the flexural strength of ZrB2 matrix composites can be increased by 25% by the introduction of inclusions of specially selected refractory strengthening phases. Dependence of the normalized strength of composites ZrB2–B4C on the logarithm of normalized strain rate can be described by a power law in the range of strain rates from 10^-3 to 10^6 1/s and temperatures from 295 K to ~1673 K. Results of simulation confirm that the technologies of SLS and SPS can be used for the production of UHTC composites with high values of the specific strength and the fracture toughness.