The present paper analyzed the microstructural characteristics and the mechanical properties of a Ti–Nb–Zr–Fe–O alloy of β-Ti type obtained by combining severe plastic deformation (SPD), for which the total reduction was of ε_tot = 90%, with two variants of super-transus solution treatment (ST). The objective was to obtain a low Young’s modulus with sufficient high strength in purpose to use the alloy as a biomaterial for orthopedic implants. The microstructure analysis was conducted through X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) investigations. The analyzed mechanical properties reveal promising values for yield strength (YS) and ultimate tensile strength (UTS) of about 770 and 1100 MPa, respectively, with a low value of Young’s modulus of about 48–49 GPa. The conclusion is that satisfactory mechanical properties for this type of alloy can be obtained if considering a proper combination of SPD + ST parameters and a suitable content of β-stabilizing alloying elements, especially the Zr/Nb ratio.

The present study investigates the influence of hot-deformation, above β-transus and different thermal treatments on the microstructural and mechanical behaviour of a commercially available Ti-6246 titanium-based alloy, by SEM (scanning electron microscopy), tensile and microhardness testing techniques. The as-received Ti-6246 alloy was hot-deformed—HR by rolling, at 1000 °C, with a total thickness reduction (total deformation degree) of 65%, in 4 rolling passes. After HR, different thermal (solution—ST and ageing—A) treatments were applied in order to induce changes in the alloy’s microstructure and mechanical behaviour. The applied solution treatments (ST) were performed at temperatures below and above β-transus (α → β transition temperature; approx. 935 °C), to 800 °C, 900 °C and 1000 °C respectively, while ageing treatment at a fixed temperature of 600 °C. The STs duration was fixed at 27 min while A duration at 6 h. Microstructural characteristics of all thermomechanical (TM) processed samples and obtained mechanical properties were analysed and correlated with the TM processing conditions. The microstructure analysis shows that the applied TM processing route influences the morphology of the alloy’s constituent phases. The initial AR microstructure shows typical Widmanstätten/basket-weave-type grains which, after HR, are heavily deformed along the rolling direction. The STs induced the regeneration of α-Ti and β-Ti phases, as thin alternate lamellae/plate-like structures, showing preferred spatial orientation. Also, the STs induced the formation of α′-Ti/α″-Ti martensite phases within parent α-Ti/β-Ti phases. The ageing treatment (A) induces reversion of α′-Ti/α″-Ti martensite phases in parent α-Ti/β-Ti phases. Mechanical behaviour showed that both strength and ductility properties are influenced, also, by applied TM processing route, optimum properties being obtained for a ST temperature of 900 °C followed by ageing (ST2 + A state), when both strength and ductility properties are at their maximum (σ_UTS = 1279 ± 15 MPa, σ_0.2 = 1161 ± 14 MPa, ε_f = 10.1 ± 1.3%).

In this present study, the influence of solution annealing temperature on microstructural properties of a forged Super Duplex Stainless Steel (SDSS) was investigated by SEM-BSE (Scanning Electron Microscopy-Backscattered Electrons) and SEM-EBSD (Scanning Electron Microscopy-Electron Backscatter Diffraction) techniques. A brief solution treatment was applied to the forged super duplex alloy, at different temperatures between 800 °C and 1100 °C, with a constant holding time of 0.6 ks (10 min). Microstructural characteristics such as nature, weight fraction, distribution and morphology of constituent phases, average grain-size and grain misorientation were analysed in relation to the solution annealing temperature. Experimental results have shown that the constituent phases in the SDSS alloy are δ-Fe, γ-Fe and σ (Cr-Fe) and that their properties are influenced by the solution treatment temperature. SEM examinations revealed microstructural modifications induced by the Cr rich precipitates along the δ/γ and δ/δ grain boundaries, which may significantly affect the toughness and the corrosion resistance of the alloy. Solution annealing at 1100 °C led to complete dissolution of σ (Cr-Fe) phase, the microstructure being formed of primary δ-Fe and γ-Fe. The orientation relationship between δ/δ, γ/γ and δ/γ grains was determined by electron back scattering diffraction (EBSD). Both primary constituent phase’s microhardness and global microhardness were determined.

In this present study, the influence of isothermal aging temperature and duration on microstructural and mechanical properties of a hot-deformed UNS S32750 super duplex stainless steel (SDSS) alloy was investigated by SEM-EBSD (scanning electron microscopy-electron backscatter diffraction) and tensile testing techniques. An isothermal aging treatment, at temperatures between 400 and 600 °C and treatment duration between 3 and 120 h, was applied to a commercial UNS S32750 SDSS alloy. Microstructural characteristics of all thermomechanical (TM) processed states, such as distribution and morphology of constituent phases, grain’s modal orientation (MO), and obtained mechanical properties were analysed correlated with the TM processing conditions. The obtained experimental results show that the constituent phases, in all TM processed states, are represented by elongated γ-phase grains within the δ-phase matrix. The R-phase was observed in the case of aging treatment performed at 600 °C for 120 h. Within the δ-phase matrix, dynamically recrystallized grains were identified as a result of applying hot deformation and isothermal aging treatments. Also, it was observed that aging treatment parameters can significantly influence the mechanical behaviour exhibited by the UNS S32750 SDSS alloy, in terms of elongation to fracture and absorbed energy during impact testing.

The deformation temperature of Super-Duplex Stainless Steels (SDSS) is a key factor defining the number of phases, their proportions, and their arrangement in space, with the main role for the hot plastic processing on the industrial scale. The main scope of the study was to determine the optimal forging temperature of UNS S32750 Super-Duplex Stainless Steel by means of the SEM-EBSD technique. The alloy was forged at different temperatures between 800 °C and 1300 °C, after which the most representative samples were analysed by SEM-EBSD. Microstructural characteristics as nature, distribution, morphology, and relative proportion of constituent phases, grain form, homogeneity, and dynamic recrystallization of the structure were analysed in relation to forging temperature. Primary phases as δ-Fe and γ-Fe were identified in all structural states of the steel, irrespective of the deformation temperature. Secondary phases σ-(Cr-Fe) and χ-(Fe-Cr-Mo), identified only under 1050 °C, have a strong negative effect on hot formability because they are fragile. The conclusion was that the optimal forging temperature range for the UNS S32750 steel is 1050–1300 °C because between these temperatures the structure is composed only of ferrite and austenite, without other harmful secondary alloy phases. Due to the dynamic recrystallization, the plasticity of the material also increases in this thermal range.

The super-duplex stainless steel UNS S32750 consists of two main phases, austenite and ferrite, which differ not only by their morphology, physical, and mechanical properties, but also by their deformation behaviour. A heterogenous deformation can be obtained during thermomechanical processing, generating internal stresses and sometimes fissures or cracks on sample lateral surfaces, due to ferrite’s phase lower potential of plastic deformation accommodation in comparison with austenite phase. The research objective is to determine the optimum range of the applied deformation degree, during hot deformation processing by upsetting of the super-duplex steel (SDSS) UNS S32750. In the experimental program several samples were hot deformed by upsetting, by applying a deformation degree between 5–50%, at 1050 °C and 1300 °C. The most representative hot-deformed samples were selected and analysed by scanning electron microscope-Electron Backscatter Diffraction (SEM-EBSD), to determine the main microstructural characteristics obtained during thermomechanical processing. When considering the experimental results, the influence of the applied deformation degree on the microstructure has been evaluated. Microstructural features, such as nature, distribution, morphology and relative proportion of constituent phases, Grain Reference Orientation Deviation (GROD), and recrystallization (RX), were analysed, in correlation with the applied deformation degree. Finally, it was concluded that the UNS S32750 alloy can be safely hot deformed, by upsetting, at 1050 °C and 1300 °C, with a maximum applied deformation degree of 20% at 1050 °C and, respectively, by 50% at 1300 °C.