Phase transformations during cooling in α+β titanium alloys

Ahmed, Tauseef; Rack, H.J.

doi:10.1016/s0921-5093(97)00802-2

Cited by 965 publications

(412 citation statements)

References 7 publications

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“…20) As shown in Fig. 3(b), Ti-6Al-7Nb has an acicular martensitic morphology with high-temperature -phase grain boundaries barely visible.…”

mentioning

confidence: 82%

“…This acicular martensitic morphology is similar to that observed by Ahmed and Rack, who claimed that a high cooling rate is required for Ti-6Al-4V to attain a martensitic morphology. 20) According to Filip et al, 21) a completely martensitic structure could be obtained at a cooling rate >18 K/s. This suggests that the cooling rate for the proposed casting process should be at least as high as 18 K/s.…”

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confidence: 99%

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Comparison among Mechanical Properties of Investment-Cast c.p. Ti, Ti-6Al-7Nb and Ti-15Mo-1Bi Alloys

Lin

2004

Mater. Trans.

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The present study compares castability and mechanical performance among alloys of c.p. Ti, Ti-6Al-7Nb and a newly-developed Ti-15Mo-1Bi in regard to their as-cast state. Experimental results indicate that average cast length of Ti-6Al-7Nb appears a little lower than c.p. Ti and Ti-15Mo-1Bi, although the differences are not significant. C.p. Ti has an hcp phase of lath-type morphology with serrated, irregular grain boundaries. Ti-6Al-7Nb is dominated by hexagonal 0 phase with acicular martensitic morphology. In particular, Ti-15Mo-1Bi is comprised of equiaxed, metastable bcc phase. The hardened layer thicknesses of three materials are similar. Ti-15Mo-1Bi has the highest surface microvickers hardness, while c.p. Ti has the lowest. The bulk hardness of c.p. Ti is much lower than the other two alloys which display similar hardness. Notably, Ti-15Mo-1Bi and Ti-6Al-7Nb have similar bending strength which is far higher than c.p. Ti. The bending modulus of Ti-15Mo-1Bi is significantly lower than c.p. Ti and Ti-6Al-7Nb. Ti-15Mo-1Bi also shows a much larger elastic recovery angle than two other materials. Tensile test indicates that Ti-15Mo-1Bi has a similar UTS but much higher YS and elongation along with much lower tensile modulus compared to Ti-6Al-7Nb.

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“…20) As shown in Fig. 3(b), Ti-6Al-7Nb has an acicular martensitic morphology with high-temperature -phase grain boundaries barely visible.…”

mentioning

confidence: 82%

mentioning

confidence: 99%

Comparison among Mechanical Properties of Investment-Cast c.p. Ti, Ti-6Al-7Nb and Ti-15Mo-1Bi Alloys

Lin

2004

Mater. Trans.

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“…The 3D micro-CT reconstructed models of the SLM-built Gyroid TPMS structures were superimposed on their 3D CAD models for both visual and quantifiable comparisons, as shown in that Ti-6Al-4V samples have entirely martensitic α' phase when exposed to cooling rates higher than 525 K/s (Ahmed and Rack, 1998). In the SLM process, the materials processed undergo a very high cooling rate with the order of 10 6 K/s (Thijs et al 2010).…”

Section: Figure 4 Sem Images Of Strut Surface Of the Ti-6al-4v Tmps Cmentioning

confidence: 99%

Ti–6Al–4V triply periodic minimal surface structures for bone implants fabricated via selective laser melting

Yan

Hao

Hussein

et al. 2015

Journal of the Mechanical Behavior of Biomedical Materials

558

236

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Young, Ti-6Al-4V triply periodic minimal surface structures for bone implants fabricated via selective laser melting, Journal of the Mechanical Behavior of Biomedical Materials, http://dx.doi.org/10.1016/j.jmbbm. 2015.06.024 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. C for 4 h, the α' martensite was converted to a mixture of α and β, in which the α phase being the dominant fraction is present as fine laths with the width of 500-800 nm and separated by a small amount of narrow, interphase regions of dark β phase. Also, the microhardness is decreased to 3.71±0.35 GPa due to the coarsening of the microstructure. The 80-95% porosity TPMS lattices exhibit a comparable porosity with trabecular bone, and the modulus is in the range of 0.12-1.25 GPa and thus can be adjusted to the modulus of trabecular bone. At the same range of porosity of 5-10%, the moduli of cortical bone and of the Ti-6Al-4V TPMS lattices are in a similar range. Therefore, the modulus and porosity of Ti-6Al-4V TPMS lattices can be tailored to the levels of human bones and thus reduce or avoid "stress shielding"and increase longevity of implants. Due to the biomorphic designs, and high interconnected porosity and stiffness comparable to human bones, SLM-made Ti-6Al-4V TPMS lattices can be a promising material for load bearing bone implants.

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“…The precipitation of grain boundary a phase is usually observed at a cooling rate less than 683 K/s (410°C/s). [36] Titanium has a low heat conductivity coefficient and, thus, has a relatively low cooling rate during solidification, particularly for the thicker (5.1 mm) section. The appearance of a thin grain boundary a phase layer along the prior-b grain boundaries in the FZ of the 5.1-mm-thick welds suggests that the cooling rate is slightly less than 683 K/s (410°C/s) during cooling after laser welding.…”

Section: B Defectsmentioning

confidence: 99%

“…In contrast, the absence of the grain boundary a phase along the prior-b grain boundaries in the FZ of the 3.2-mmthick welds suggests that the cooling rate after laser welding is greater than 683 K/s (410°C/s). Hence, considering that the critical cooling rate for displacive to diffusional transformation is approximately 683 K/s (410°C/s) in Ti-6Al-4V, [36] the FZ of the 5.1-mm-thick welds most likely consists of more Widmansta¨tten a relative to the 3.2-mm-thick welds, which may be mostly martensitic. Previous work on electron beam welding of Ti-6Al-4V [37] has indicated that increasing the fraction of Widmansta¨tten relative to martensitic a¢ improves the ductility.…”

Section: B Defectsmentioning

confidence: 99%

Effect of Postweld Heat Treatment on Microstructure, Hardness, and Tensile Properties of Laser-Welded Ti-6Al-4V

Kabir

Cao

Gholipour

et al. 2012

Metall Mater Trans A

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The effects of postweld heat treatment (PWHT) on 3.2-mm-and 5.1-mm-thick Ti-6Al-4V butt joints welded using a continuous wave (CW) 4-kW Nd:YAG laser welding machine were investigated in terms of microstructural transformations, welding defects, and hardness, as well as global and local tensile properties. Two postweld heat treatments, i.e., stress-relief annealing (SRA) and solution heat treatment followed by aging (STA), were performed and the weld qualities were compared with the as-welded condition. A digital image correlation technique was used to determine the global tensile behavior for the transverse welding samples. The local tensile properties including yield strength and maximum strain were determined, for the first time, for the laser-welded Ti-6Al-4V. The mechanical properties, including hardness and the global and local tensile properties, were correlated to the microstructure and defects in the as-welded, SRA, and STA conditions.

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Phase transformations during cooling in α+β titanium alloys

Cited by 965 publications

References 7 publications

Comparison among Mechanical Properties of Investment-Cast c.p. Ti, Ti-6Al-7Nb and Ti-15Mo-1Bi Alloys

Comparison among Mechanical Properties of Investment-Cast c.p. Ti, Ti-6Al-7Nb and Ti-15Mo-1Bi Alloys

Ti–6Al–4V triply periodic minimal surface structures for bone implants fabricated via selective laser melting

Effect of Postweld Heat Treatment on Microstructure, Hardness, and Tensile Properties of Laser-Welded Ti-6Al-4V

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