An Investigation of the Development of Coarse Grains During β Annealing of Hot-Forged Ti-6Al-4V

Levkulich, N. C.; Semiatin, S. L.; Payton, E.J.; Srivatsa, Shesh; Pilchak, Adam L.

doi:10.1007/s11661-021-06158-z

Cited by 9 publications

(2 citation statements)

References 20 publications

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“…If barrelling cannot be avoided by careful design of experiments, Ômodeling the testÕ is necessary, leading to the circularity in constitutive data discussed above. To account for non-uniform deformation and barrelling, a number of authors have proposed correction methods for r e ð Þ data obtained from hot upsetting-these were recently reviewed by the authors in connection with a dilatometer study on hot compression of ZrNb alloys (Ref 18 26) for plane strain transverse hot compression of Ti64 cylinders. In this analysis, friction and heat transfer parameters were chosen to match the load-displacement data, but the authors also state that the flow stress data were Ôextrapolated to high strain and tunedÕ to fit the load-displacement data.…”

Section: Barrelling and Flow Stress Correction Proceduresmentioning

confidence: 99%

Finite Element Modeling of Hot Compression Testing of Titanium Alloys

Jedrasiak

Shercliff

Mishra

et al. 2022

J. of Materi Eng and Perform

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This paper presents experimental results and finite element analysis of hot upsetting of titanium alloys Ti64 and Ti407 using a dilatometer in loading mode. All samples showed barrelling, as a consequence of an inhomogeneous temperature distribution and friction. The FE analysis is a full thermomechanical model of the test calibrated using multiple thermocouples. At each nominal temperature and strain rate, the true flow stress–strain response is inferred using the difference between the initially assumed constitutive response input to the FE analysis, $$\sigma =f\left(T,\dot{\varepsilon },\varepsilon \right)$$ σ = f T , ε ˙ , ε , and the predicted response of the model. The analysis applies new procedures for: (1) modeling the thermal gradient; (2) finding the flow stress correction due to the inhomogeneity, using literature data as the input to the FE analysis; and (3) smoothing the constitutive data, fitting empirical $$\sigma =f\left(T,\dot{\varepsilon }\right)$$ σ = f T , ε ˙ surfaces at multiple discrete strains. The extracted true constitutive data confirm the moderate strain-softening behavior in Ti64 alloy, and the FE model predicts the distribution of local deformation conditions, for application in interpretation of microstructure and texture evolution. This highlights the difference between nominal and actual test conditions, showing that the discrepancy varies systematically with test conditions, with the central strain and strain rate being magnified significantly, by factors of order 2–3.

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Section: Barrelling and Flow Stress Correction Proceduresmentioning

confidence: 99%

Finite Element Modeling of Hot Compression Testing of Titanium Alloys

Jedrasiak

Shercliff

Mishra

et al. 2022

J. of Materi Eng and Perform

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“…Under certain circumstances, improper selection of forging variables may result in the formation of a deleterious, coarse-b-grain structure during subsequent b annealing in Ti-6Al-4V. [11] The present work was designed therefore to meet two principal objectives: (1) To establish the level of deformation heating during high rate deformation processing of Ti-6Al-4V and (2) to determine how such heating transients affect the evolution of the a and b phases. To meet these objectives, instrumented, hot-compression tests were performed at various temperatures in a screw press, and the resulting microstructures were measured and interpreted in terms of the associated temperature transients.…”

Section: High-integrity Structural Components Arementioning

confidence: 99%

Effect of Deformation Heating on Microstructure Evolution During Hot Forging of Ti-6Al-4V

Kulakov

Rahimi

Semiatin

2021

Metall Mater Trans A

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The effect of deformation heating on microstructure evolution during hot forging of Ti-6Al-4V was established. For this purpose, right-circular cylinders of Ti-6Al-4V with an equiaxed-α preform microstructure were preheated to a temperature between 1148 K (875 °C) and 1223 K (950 °C), and compressed to a 60-pct. height reduction in a screw press, yielding average true strain rates of ~ 5 to 20 s−1. Thermocouple measurements and corroborating finite-element-method (FEM) simulations quantified substantial deformation-heating-induced temperature increases. For all preheat temperatures, the heating transient led to an exposure above the equilibriumβ transus temperature. Despite such temperature excursions, the volume fraction of equiaxed primary α in each forged billet was only slightly lower than that in the corresponding preheated condition. The source of such observations was rationalized on the basis of the (hypothesized) solute-concentration fields that develop during the heating and cooling transients experienced in high-rate deformation processing.

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