The effect of cooling rates on the microstructure and mechanical properties of thermo-mechanically processed Ti–Al–Mo–V–Cr–Fe alloys

Abstract

The effect of cooling rates on the microstructure and mechanical properties of thermo-mechanically processed Ti-Al-Mo-V-Cr-Fe alloys AbstractTwo near-β titanium alloys, Ti-5Al-5Mo-5V-1Cr-1Fe and a modified one containing 2 wt% Cr (Ti-5Al-5Mo-5V-2Cr-1Fe) were produced from Ti hydride precursor powders via the cost-effective blended elemental powder metallurgy technique. The effects of two cooling rates (10 K s−1 and 1 K s−1) during thermo-mechanical processing on the microstructure and mechanical properties were investigated using X-ray diffraction and scanning electron microscopy. X-ray line profile analysis revealed that dislocation densities and microstrain in β-Ti phase are higher than in α-Ti phase for all cases. In both alloys, slower cooling results in an increase in α volume fraction and promotes morphology of continuous grain boundary α phase. A lower total elongation is obtained in both alloys under slower cooling which could be accounted for by the continuous morphology of α phase. Overall, Ti-5Al-5Mo-5V-1Cr-1Fe displays higher ultimate tensile strength and total elongation compared to Ti-5Al-5Mo-5V-2Cr-1Fe, regardless of the cooling rate. Two near-β titanium alloys, Ti-5Al-5Mo-5V-1Cr-1Fe and a modified one containing 2 wt. % Cr (Ti-5Al-5Mo-5V-2Cr-1Fe) were produced from Ti hydride precursor powders via the cost-effective blended elemental powder metallurgy technique. The effects of two cooling rates (10 Ks -1 and 1 Ks -1 ) during thermo-mechanical processing on the microstructure and mechanical properties were investigated using X-ray diffraction and scanning electron microscopy. X-ray line profile analysis revealed that dislocation densities and microstrain in β-Ti phase are higher than in α-Ti phase for all cases. In both alloys, slower cooling results in an increase in α volume fraction and promotes morphology of continuous grain boundary α phase. A lower total elongation is obtained in both alloys under slower cooling which could be accounted for by the continuous morphology of α phase. Overall, Ti-5Al-5Mo-5V-1Cr-1Fe displays higher ultimate tensile strength and total elongation compared to Ti-5Al-5Mo-5V-2Cr-1Fe, regardless of the cooling rate.

The influence of partitioning on the growth of intragranular α in near-β Ti alloys

“…The b grains became elongated during the deformation at 1073 K, and thus the allotriomorphic a phase is curved. The volume fraction of a, measured by XRD in our previous study [33] (both allotriomorphic and intragranular) is 22 ± 3% after TMP, increases to 38 ± 6% for the samples aged at 923 K for 60 min and reaches 50 ± 3% after 240 min. TEM specimens were analysed along the [1 1 0] b axis in order to view the intragranular a plates edge-on [34].…”

Enhanced fatigue behavior of powder metallurgy Ti–6Al–4V alloy by applying ultrasonic impact treatment

“…Specimens of Ti-6Al-4V alloy used in this study were prepared by means of the following route of the cost-effective blended elemental PM technique [5][6][7][8][24][25][26]. Hydrogenated (3.5 wt% H) Ti powder (the particle size is 100 μm) were mixed with 60Al-40V master alloy powder (the particle size is 40-63 μm) to obtain the required alloy composition.…”

“…Further development of the PM approach was consisted in the use of titanium hydride as a basis of powder mixtures. It was shown that titanium hydride had a positive impact on the final density, and chemical and microstructural homogeneity of PM titanium alloys of different phase compositions [5][6][7][8].…”

Effect of Fe Content on the Microstructure and Mechanical Properties of Ti-Al-Mo-V-Cr-Fe Alloys

“…The white circle in Fig. 3(b) indicates the grown secondary α and β phase region [14]. To analyze the shape of the α phase in the white circle, these specimens were etched by Kroll's reagent.…”