The effect of omega phase on the mechanical properties of titanium alloys

“…The embrittling effects of the ω phase are thought to be because dislocations stop or bend around ω particles, leaving high dislocation densities in the β matrix [137]. When dislocations do move through the ω phase, they shear the ω phase, creating slip bands that can lead to crack nucleation at low macroscopic strains [139], as shown in Figure 10.…”

Section: Effect Of the ω Phase On Mechanical Propertiesmentioning

confidence: 99%

“…Feeney and Blackburn [136] found that β + ω microstructures in a Ti-11.5Mo-6Zr-4.5Sn alloy exhibited strengths up to 1500 MPa. Williams et al [137] found that the yield strength of Ti-10Mo (at%), Ti-25 V (at%), Ti-8Mn (at%), and β III alloys increased when the ω phase was present and decreased when the α phase became the dominant phase. Alloys that deform via the ω transformation also exhibit higher yield strengths than alloys that deform via twins [51].…”

Section: Effect Of the ω Phase On Mechanical Propertiesmentioning

confidence: 99%

“…The increase in elastic modulus and tensile strength due to the ω phase is accompanied by embrittlement. In tension, embrittlement is shown by a decrease in elongation to failure (ϵ f ) when ω microstructures are present, as Zhao et al [31], Mantri et al [112], Williams et al [137], Wang et al [125], and Feeney and Blackburn [136] documented in alloys that had precipitated the isothermal ω phase. The decrease can be seen the most clearly in Zhao et al’s [31] Ti-18V alloy in Table 4 and is also demonstrated by the drop in ϵ f from ∼35% to <5% with ω iso precipitation in Mantri et al’s [112] Ti-12Mo alloy.…”

Section: Effect Of the ω Phase On Mechanical Propertiesmentioning

confidence: 99%

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A review of the metastable omega phase in beta titanium alloys: the phase transformation mechanisms and its effect on mechanical properties

Ballor

Prima

et al. 2022

International Materials Reviews

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Since its discovery in 1954, the omega (ω) phase in titanium and its alloys has attracted substantial attention from researchers. The β-to-ω and ω-to-α phase transformations are central to β-titanium alloy design, but the transformation mechanisms have been a subject of debate. With new generations of aberration-corrected transmission electron microscopy and atom probe tomography, both the spatial resolution and compositional sensitivity of phase transformation analysis have been rapidly improving. This review provides a detailed assessment of the new understanding gained and related debates in this field enabled by advanced characterization methods. Specifically, new insights into the possibility of a coupled diffusional-displacive component in the β-to-ω transformation and key nucleation driving forces for the ω-assisted α phase formation are discussed. Additionally, the influence of ω phase on the mechanical properties of β-titanium alloys is also reviewed. Finally, a perspective on open questions and future direction for research is discussed.

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“…The formation of α″ martensite under rapid quenching tends to reduce hardness, tensile, and fatigue strength [ 18 , 35 , 36 , 37 , 38 ]. Additionally, the ω phase is strengthening the titanium alloy in a certain volume fraction range, but also can lead to embrittlement [ 39 , 40 ]. Heat treatments of metastable β titanium alloys show promising features to improve and enhance the mechanical properties and are considered for different fields of applications, including aerospace or medical applications [ 22 , 26 , 41 , 42 ].…”

Section: Introductionmentioning

confidence: 99%

Heat Treatments of Metastable β Titanium Alloy Ti-24Nb-4Zr-8Sn Processed by Laser Powder Bed Fusion

et al. 2022

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Titanium alloys, especially β alloys, are favorable as implant materials due to their promising combination of low Young’s modulus, high strength, corrosion resistance, and biocompatibility. In particular, the low Young’s moduli reduce the risk of stress shielding and implant loosening. The processing of Ti-24Nb-4Zr-8Sn through laser powder bed fusion is presented. The specimens were heat-treated, and the microstructure was investigated using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mechanical properties were determined by hardness and tensile tests. The microstructures reveal a mainly β microstructure with α″ formation for high cooling rates and α precipitates after moderate cooling rates or aging. The as-built and α″ phase containing conditions exhibit a hardness around 225 HV5, yield strengths (YS) from 340 to 490 MPa, ultimate tensile strengths (UTS) around 706 MPa, fracture elongations around 20%, and Young’s moduli about 50 GPa. The α precipitates containing conditions reveal a hardness around 297 HV5, YS around 812 MPa, UTS from 871 to 931 MPa, fracture elongations around 12%, and Young’s moduli about 75 GPa. Ti-24Nb-4Zr-8Sn exhibits, depending on the heat treatment, promising properties regarding the material behavior and the opportunity to tailor the mechanical performance as a low modulus, high strength implant material.

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The effect of omega phase on the mechanical properties of titanium alloys

Cited by 185 publications

References 3 publications

Influence of cooling rate on the precipitation kinetics of nanoscale isothermal ω-phase in metastable β-Ti alloy, Ti–5Al–5Mo–5V–3Cr

Influence of cooling rate on the precipitation kinetics of nanoscale isothermal ω-phase in metastable β-Ti alloy, Ti–5Al–5Mo–5V–3Cr

A review of the metastable omega phase in beta titanium alloys: the phase transformation mechanisms and its effect on mechanical properties

Heat Treatments of Metastable β Titanium Alloy Ti-24Nb-4Zr-8Sn Processed by Laser Powder Bed Fusion

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