CE08 - Matériaux métalliques et inorganiques et procédés associés

Study in Titanium Alloys of Multiaxial Processing – STAMP

Study in Titanium Alloys of Multiaxial Processing (STAMP)

High temperature deformation effects on the globularization of Ti64 alloy: experimental et numerical study.

Development of experimental et numerical modelling andcaracterization methods of workhardened and recovered Ti64 microstructure.

In the aim of improving the industrial forging routes for titanium components, the STAMP project is dedicated to the study of the microstructural evolution during thermomechanical treatments of Ti64 alloys. Based on the industrial Knowledge (i.e. numerical simulation of the process), the microstructure evolution will be experimentally simulated thanks to controlled laboratory devices to reproduce the “incremental” loading of the process: sequence of stages with strain path changes and annealing. The microstructure morphology and the texture will be studied as a function of the complex thermomechanical history and will allow to understand the microstructural evolution promoting or inhibiting the ? phase globularization, mandatory for the specification in static and cyclic service conditions of titanium components

The STAMP project stems from a need of the industry: to control the microstructure so that it is as homogeneous as possible and more particularly here, the kinetics of globularization. Globularization is the process that transforms a lamellar microstructure into an equiaxed microstructure through thermomechanical treatments. The main driving force of this process is the heterogeneous deformation of the lamellae during the hot deformation of the material [Weiss, 1986]. Zherebstov [Zherebstov, 2011] and [Fan, 2018] have shown that the globularization process continues during static heat treatment by the action of recrystallization / restoration mechanisms.
The difficulty in reproducing the industrial process in the laboratory to study the kinetics of globularization and the development of macrozones lies in its multiaxial and incremental character. The MaxStrain module of the Gleeble physical simulation system offers the opportunity to get closer to the industrial process by allowing the realization of automated and instrumented bi-axial and incremental tests. It allows the study of microstructural evolutions during thermomechanical treatments that are closer to the industrial process.

The first part of the project allowed the deployment of the defined program:
- the definition of the industrial problematic and the academic expectations of the project, namely the study in laboratory conditions of the thermomechanical treatments and globularization of TA6V alloys.
- the implementation of thermomechanical tests on the Schenck machine in Mines Saint-Etienne and on the Max Strain module of the Gleeble machine at INSA in Lyon. The thermomechanical conditions are mastered and the deviations from the target path are precisely characterized; Samples are now available for analysis of the effects of globularization.
- the development of macroscopic models of the Gleeble test and microscopic models of the Ti64 deformation to accompany the study of globularization phenomena.
- Finally, the fine characterization of the initial raw microstructures of deformation and post-annealing where appropriate, with a special focus on textures including macrozones.

The prospects of the project are in accordance with the plan initially set:
- to implement the microstructural analyses of the samples thermomechanically treated with the Gleeble machine.
- Adapt the cooling after these tests to better reproduce the conditions of the industrial process;
- to identify microstructurally the conditions allowing to reach the globularization of Ti64 alloy microstructures.
- finalize the microscopic modeling of the Ti64 deformation and issue recommendations in relation to industrial expectations in term of possible modifications of forging ranges.

Saint-Jalme, Margaux Saint, et al. “Microstructure Evolution during Multiaxial Processing of TA6V.” Materials Science Forum, vol. 1016, Trans Tech Publications, Ltd., Jan. 2021, pp. 1211–1217. Crossref, doi:10.4028/www.scientific.net/msf.1016.1211.

In the aim of improving the industrial forging routes for titanium components, the STAMP project is dedicated to the study of the microstructural evolution during thermomechanical treatments of Ti64 alloys. The present project is focused on the ? phase globularization mechanisms: i.e. the fragmentation of the initial ? lamellae into isotropic nodules. This transformation is required, among various reasons, to respect the titanium alloys end-users specifications.

Based on the industrial Knowledge of the forging process (including numerical simulations), the microstructure evolution will be experimentally simulated thanks to controlled laboratory devices to reproduce the “incremental” loading of the process: an opportunity stands, to combine the high temperature compression device for monotonic, isothermal plane strain tests, (ARMINES-SMS) and the new Gleeble MaxStrainTM modulus in MATEIS INSA allowing the reproduction of forging sequences with strain path’s changes and inter-pass annealing. A specific attention will be paid to the thermomechanical conditions temperature and strain rate homogeneity in the second device, thanks to Finite element analysis of the tools and the samples. The microstructure morphology and the texture will be studied, as a function of the complex forging routes; Microstructural analyses will account for the transformation from alpha to beta during the cooling stage after forge, thanks to specific tools developed at the LEM3 (Université de Lorraine) in charge of the task in the project. A finite element model will be developed by INSA MATEIS, to capture the effect on the mechanical properties of the globularized microstructure. This model will be fed and validated respectively by the microstructure analyses the forged samples and the exploitation of the room temperature tensile tests performed on the specimen collected in semi-industrial samples pressed by the company Aubert et Duval. As a prospect of the project this model should be also applied to capture the globularization mechanisms during the forge operation of a former lamellar microstructure.

These results will highlight the microstructure evolution mechanisms allowing (or preventing) the ? phase globularization to proceed in industrial conditions. This transformation is mandatory for the static and cyclic specifications of many aeronautic components. The industrial scale allowing the problematic definition and the evaluation of the investigation results relevancy will be strongly coupled with the laboratory context easing access to microstructure analyses and versatile use of the thermo-mechanical devices.

Project coordination

Christophe DESRAYAUD (ARMINES)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

ARMINES (SMS) : Sciences des Matériaux et des Structures ARMINES
AUBERT & DUVAL
LEM3 Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux
MATEIS Matériaux : Ingénierie et Science

Help of the ANR 440,089 euros
Beginning and duration of the scientific project: October 2018 - 48 Months

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