Phase Transformation of &amp;alpha;&amp;Prime; Martensite Structure by Aging in Ti-8 mass%Mo Alloy

Mantani, Yoshikazu; Takemoto, Yoshito; Hida, Moritaka; Sakakibara, Akira; Tajima, Mamoru

doi:10.2320/matertrans.45.1629

Cited by 63 publications

(20 citation statements)

References 11 publications

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“…is reported in the specimens quenched from the temperature above the BTT. [21,22] Figure 4 also shows the presence of pit like feature in all the specimens heat treated at different temperatures. These features are identified as complex phosphides by the EDS analysis as shown in Figure 4(g).…”

Section: Methodsmentioning

confidence: 89%

“…It is reported that when the b-titanium alloys are rapidly cooled from the heat treatment temperatures above BTT, i.e., from 100 pct b-phase, the quench strains are sufficient to cause the shear transformation of orthorhombic martensite, a¢¢. [21,22] …”

Section: A Microstructural Investigationsmentioning

confidence: 99%

“…The decrease in the shear anisotropy parameter in the specimens heat treated beyond BTT may be attributed to the presence of stressinduced martensite, a¢¢ at a few locations, as seen in Figure 4(f). [21,22] To better understand and correlate the shear anisotropy parameter with the microstructural changes, the variation in the shear anisotropy parameter with the a-phase volume fraction is analyzed for the specimens heat treated below the BTT, as shown in Figure 13. The shear anisotropy parameter for the bannealed specimen is 0.0739, and theoretically, it can be assumed that the shear anisotropy parameter becomes zero when the volume fraction of the a-phase precipitation reaches 100 pct.…”

Section: B Ultrasonic Velocitiesmentioning

confidence: 99%

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Ultrasonic Characterization of Microstructural Changes in Ti-10V-4.5Fe-1.5Al β-Titanium Alloy

Viswanath

Kumar

Jayakumar

et al. 2015

Metall Mater Trans A

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Ultrasonic measurements have been carried out in Ti-10V-4.5Fe-1.5Al b-titanium alloy specimens subjected to b annealing at 1173 K (900°C) for 1 hour followed by heat treatment in the temperature range of 823 K to 1173 K (550°C to 900°C) at an interval of 50 K (50°C) for 1 hour, followed by water quenching. Ultrasonic parameters such as ultrasonic longitudinal wave velocity, ultrasonic shear wave velocity, shear anisotropy parameter, ultrasonic attenuation, and normalized nonlinear ultrasonic parameter have been correlated with various microstructural changes to understand the interaction of the propagating ultrasonic wave with microstructural features in the alloy. Simulation studies using JMatPro Ò software and X-ray diffraction measurements have been carried out to estimate the a-phase volume fraction in the specimens heat treated below the b-transus temperature (BTT). It is found that the a-phase (HCP) volume fraction increases from 0 to 52 pct, with decrease in the temperature from 1073 K to 823 K (800°C to 550°C). Ultrasonic longitudinal and shear wave velocities are found to increase with decrease in the heat treatment temperature below the BTT, and they exhibited linear relationships with the a-phase volume fraction. Thickness-independent ultrasonic parameters, Poisson's ratio, and the shear anisotropy parameter exhibited the opposite behavior, i.e., decrease with increase in the a-phase consequent to decrease in the heat treatment temperature from 1073 K to 823 K (800°C to 550°C). Ultrasonic attenuation is found to decrease from 0.7 dB/mm for the b-annealed specimen to 0.23 dB/mm in the specimen heat treated at 823 K (550°C) due to the combined effect of the decrease in the b-phase (BCC) with higher damping characteristics and the reduction in scattering due to randomization of b grains with the precipitation of a-phase. Normalized nonlinear ultrasonic parameter is found to increase with increase in the a-phase volume fraction due to increased interfacial strain. For the first time, quantitative correlations established between various ultrasonic parameters and the volume fraction of a-phase in a b-titanium alloy are reported in the present paper. The established correlations are useful for estimation of volume fraction of a-phase in heat-treated btitanium alloy, by nondestructive ultrasonic measurements.

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Section: Methodsmentioning

confidence: 89%

Section: A Microstructural Investigationsmentioning

confidence: 99%

Section: B Ultrasonic Velocitiesmentioning

confidence: 99%

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Ultrasonic Characterization of Microstructural Changes in Ti-10V-4.5Fe-1.5Al β-Titanium Alloy

Viswanath

Kumar

Jayakumar

et al. 2015

Metall Mater Trans A

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“…The deformed microstructures were observed using the electron backscatter diffraction (EBSD) method in a scanning electron microscope (SEM, Quanta TM 250-FEI) operated at 20 kV. The experimental lattice parameters for EBSD measurement are as follows: a = 3.01 Å, b = 4.98 Å, c = 4.65 Å for α ′′ (orthorhombic) phase 16) , a = 3.31 Å for β phase 17) , and a = 4.62 Å, c = 2.81 Å for ω phase 18) . The EBSD-based crystal orientation map data was analyzed using Orientation-Imaging Microscopy (OIM TM ) equipped with an EBSD measurement system (TexSEM Laboratories Inc., TSL).…”

Section: Methodsmentioning

confidence: 99%

Stress-Induced α″ Martensitic Transformation Mechanism in Deformation Twinning of Metastable β-Type Ti-27Nb-0.5Ge Alloy under Tension

Lee

Kim

et al. 2016

Mater. Trans.

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In this study, the formation mechanism of the stress-induced α ′′ martensitic phase in the deformation twinning (DT) band of metastable β-type Ti-27Nb-0.5Ge (at.%) alloy under tension was investigated. A preferential nucleation site for the stress-induced α ′′ martensitic transformation is inside a DT band with high dislocation density. The α ′′ martensitic phase developed in the DT band with increasing applied plastic strain. The α ′′ martensitic phase subsequently grew to intersect other DT bands, forming secondary DT bands themselves in the parent β grains.

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“…As a result, the structure of 00 martensite in this alloy is discussed first here. Orthorhombic martensite was reported to have either a face-centered 13,14) or a base-centered [15][16][17] structure in titanium alloys. In this study, the crystal structure of 00 has been identified as a base-centered (centered on the C face) orthorhombic lattice.…”

Section: Microstructure Of the Water-quenched Weldsmentioning

confidence: 99%

Microstructure and Notch Properties of Heat-Treated Ti-4.5Al-3V-2Mo-2Fe Laser Welds

2009

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The microstructure and transformation behavior of Ti-4.5Al-3V-2Mo-2Fe alloy and its laser welds after various heat treatments were investigated. Notch properties, such as impact toughness and notched tensile strength, were also measured on the welds to choose an appropriate post-weld heat treatment (PWHT) of the alloy. The temperature regimes in which transformed into 0 , 00 or retained as after quenching were identified and discussed. The results indicated that 00 could be obtained primarily by rapid quenching from 880$840 C solution temperatures and was identified as a base-centered orthorhombic (centered on the C face) with the lattice parameters of a ¼ 0:305 nm, b ¼ 0:489 nm, and c ¼ 0:457 nm. The as-welded specimen exhibited fine acicular in the matrix with hardness considerably higher than the mill-annealed base metal. For a PWHT temperature lower than 800 C, the change in microstructure and hardness of the welds depended mainly on the temperature, not on the cooling rate. If the PWHT temperature was higher than 800 C, both the temperature and the cooling rate were important in altering microstructure and hardness of the welds. The welds after a 704 C/4 h treatment could prevent notch brittleness, reduce hardness variation in different regions of the weld, and obtain notch properties similar to the mill-annealed base metal.

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Phase Transformation of α″ Martensite Structure by Aging in Ti-8 mass%Mo Alloy

Cited by 63 publications

References 11 publications

Ultrasonic Characterization of Microstructural Changes in Ti-10V-4.5Fe-1.5Al β-Titanium Alloy

Ultrasonic Characterization of Microstructural Changes in Ti-10V-4.5Fe-1.5Al β-Titanium Alloy

Stress-Induced α″ Martensitic Transformation Mechanism in Deformation Twinning of Metastable β-Type Ti-27Nb-0.5Ge Alloy under Tension

Microstructure and Notch Properties of Heat-Treated Ti-4.5Al-3V-2Mo-2Fe Laser Welds

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