The flow behavior of metastable β titanium alloy was investigated basing on isothermal hot compression tests performed on Gleeble 3800 thermomechanical simulator at near and above β transus temperatures. The flow stress curves were obtained for deformation temperature range of 800–1100 °C and strain rate range of 0.01–100 s−1. The strain compensated constitutive model was developed using the Arrhenius-type equation. The high correlation coefficient (R) as well as low average absolute relative error (AARE) between the experimental and the calculated data confirmed a high accuracy of the developed model. The dynamic material modeling in combination with the Prasad stability criterion made it possible to generate processing maps for the investigated processing temperature, strain and strain rate ranges. The high material flow stability under investigated deformation conditions was revealed. The microstructural analysis provided additional information regarding the flow behavior and predominant deformation mechanism. It was found that dynamic recovery (DRV) was the main mechanism operating during the deformation of the investigated β titanium alloy.

The stress-strain curves for nickel-based superalloy were obtained from isothermal hot compression tests at a wide range of deformation temperatures and strain rates. The material constants and deformation activation energy of the investigated superalloy were calculated. The accuracy of the constitutive equation describing the hot deformation behavior of this material was confirmed by the correlation coefficient for the linear regression. The distribution of deformation activation energy Q as a function of strain rate and temperature for nickel-based superalloy was presented. The processing maps were generated upon the basis of Prasad stability criterion for true strains ranging from 0.2 to 1 at the deformation temperatures range of 900–1150 °C, and strain rates range of 0.01–100 s−1. Based on the flow stress curves analysis, deformation activation energy map, and processing maps for different true strains, the undesirable and potentially favorable hot deformation parameters were determined. The microstructural observations confirmed the above optimization results for the hot workability of the investigated superalloy. Besides, the numerical simulation and industrial forging tests were performed in order to verify the obtained results.

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The hot deformation behavior of Ti-10V-2Fe-3Al alloy obtained by the powder metallurgy (PM) method was investigated. Material for the research was produced by blending of elemental powders followed by uniaxial hot pressing. Thermomechanical tests of Ti-10V-2Fe-3Al compacts were carried out to determinate the stress-strain relationships at the temperature range of 800°C to 1000°C and strain rate between 0.01 and 10 s À1. Based on the dynamic material model (DMM) theory, processing maps at constant strain value were developed using data obtained from hot compression tests. The processing maps were elaborated for the final strain value, which was 0.9, and with flow instability criterion domains applied to it. Two critical regions associated with the flow behavior of the investigated material were revealed. Microstructural changes during hot deformation at various temperatures and strain rates were discussed. The correlation between calculated efficiency of power dissipation, flow instability criterion, and microstructure evolution was determined. The presence of defects was confirmed in regions predicted by the instability maps. The microstructure of the investigated alloy, corresponding to the high efficiency of power dissipation characterized by the occurrence of dynamic recrystallization (DRX) phenomena, was also shown. Additionally, average hardness values in relation to variable process parameters were designated. Based on the conducted studies and analysis, processing windows for Ti-10V-2Fe-3Al alloy compacts were proposed.

The influence of the induction sintering process at different temperatures on the behavior of the powder metallurgy Ti-5Al-5Mo-5V-3Cr alloy was investigated. Material for the research was produced by elemental powder blending, followed by the uniaxial cold compacting process. Powder compacts were induction heated and sintered within the temperature range of 1000 °C to 1300 °C. The influences of process parameters on the material behavior during sintering and its properties were studied. The microstructure examination was performed with particular attention to the pore size and distribution as well as the homogenization of the microstructure. The sintering temperature of 1200 °C proved to be critical for the dissolution of most alloying powder particles. Hot compression tests were performed to determine the formability of the obtained material. Significant differences in flow stress behavior between samples sintered at temperatures below and above 1200 °C were observed. The mechanical properties of the material before and after deformation were compared. The evolution of the microstructure of sintered Ti-5Al-5Mo-5V-3Cr alloy after hot deformation was analyzed with an emphasis on its influence on the material properties. Based on the conducted research, it was found that the adequate homogenization of the chemical composition and microstructure was achieved at the temperature of 1250 °C, and a further increase did not reflect in a significant improvement.