Phase transformation of the Ti-5553 titanium alloy subjected to rapid heating

Abstract

The a ? b phase transformation upon heating in the Ti-5553 alloy with lamellar-nodular bimodal microstructure was tracked in situ with high energy X-ray diffraction. Rapid heating at 10, 50 and 100 °C s -1 from room temperature to 1050 °C was tested. Phase transformation on heating was studied by a combined analysis of the microstructural features that provides estimates of mass fractions, mean lattice parameters and full width at half maximum for the two phases. In comparison with equilibrium conditions, the experimental mass fractions reveal a shift of the transformation domain toward high temperatures when the heating rate increases. Also, the dissolution of the a phase is largely impacted by its morphology, the transformation being faster for a lamellae. The combined analysis of mean lattice parameters and full width at half maximum suggests that the a ? b phase transformation on heating is diffusion controlled. The b phase therefore inherits the solute content of the adjacent parent a phase, leading to chemical heterogeneities in the b phase regardless of the heating rate.

Material Characterization and Electrochemical Properties of Titanium Alloy 5553 Prepared by Selective Laser Melting as Processed and after Abrading and Polishing

“…Literature shows that Ti-5553 can be multidirectionally forged in the two-phase α + β field that consists of a microstructure with large globular and rodlike, needle-shaped α precipitates within the β phase matrix. [61][62][63]70 XRD data for Ti-5553 specimens used in this work indicate a largely β-phase alloy based on the higher intensity of the β-phase peaks relative to the α-phase ones.…”

“…An X-ray diffraction spectrum for a typical as-processed Ti-5553 specimen is shown in Figure . High-intensity and symmetric diffraction peaks corresponding to the β phase were present at 2θ values (deg) of 39.45 (172,771 counts, 0.52 deg fwhm), 58.54 (10,855 counts, 1.47 deg), and 72.02 (6248 counts, 2.19 deg fwhm). , The weakly intense, symmetric peak at a 2θ value of 35.45 deg (1632 counts, 0.49 deg fwhm) and asymmetric peak at a 2θ value of 85.40 deg (3254 counts, 1.33 deg fwhm) are associated with α and α″ phases, respectively. The peak assignments are based on comparison of diffraction pattern data for this alloy. ,,,, The high intensity of the peak at a 2θ of 39.45 deg indicated that the alloy has a considerable amount of β phase.…”

“…The crystal structure of pure Ti at ambient temperature and pressure is close-packed hexagonal, known as the α phase. At about 890 °C, the Ti undergoes an allotropic transformation to a BCC structure, known as the β phase. ,,− ,− This β phase remains stable at the melting temperature (1700 °C). The alloying elements can be categorized according to their stabilizing effect on the α and β phases. ,,− ,− Some alloying elements, such Al, are α stabilizers, while other elements, such as Mo, Nb, Ta, V, and Cr, are β stabilizers.…”

Electrochemical characteristic and microstructure of Ti-6Al-7Nb alloy by centrifugal casting for orthopedic implant based on ageing time variations

“…In all conditions, there is an increase and decrease in the FWHM value. The lower FWHM values in the as-cast and 6-hour aged samples indicate that these conditions exhibit lower levels of chemical inhomogeneity and internal strain [38].…”

Influence of α‐Precipitate Orientation and Distribution on the Deformation Behavior of the Additively Manufactured Metastable β‐Titanium Alloy Ti‐5553 Assessed by Cyclic Nanoindentation

“…[ 45,46 ] An additional cause can be modifications of the local microstructure due to the β → α phase transformation during the heat treatment. [ 47 ] All these processes can lead to complex residual stress/strain states. Further, the LPBF‐M process and the subsequent heat treatment promote the formation of high dislocation densities primarily in the β‐grain boundaries and in the α p ‐precipitates (Figure S2, Supporting Information).…”