QUANTITATIVE DETERMINATION OF THE TEXTURE OF Al-Li ALLOYS

HAL Id: jpa-00226603

https://hal.archives-ouvertes.fr/jpa-00226603

Submitted on 1 Jan 1987

HAL

is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire

destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

QUANTITATIVE DETERMINATION OF THE TEXTURE OF Al-Li ALLOYS

A. Vadon, C. Laruelle, J. Heizmann, P. Jeanmart

To cite this version:

A. Vadon, C. Laruelle, J. Heizmann, P. Jeanmart. QUANTITATIVE DETERMINATION OF THE TEXTURE OF Al-Li ALLOYS. Journal de Physique Colloques, 1987, 48 (C3), pp.C3-621-C3-627.

�10.1051/jphyscol:1987372�. �jpa-00226603�

Colloque C3, supplbment au n09, Tome 48, septembre 1987

QUANTITATIVE DETERMINATION OF THE TEXTURE OF A1-Li ALLOYS

A. VADON, C. LARUELLE, J . J . HEIZMANN and P. JEANMART*

CMS-LMPC, Facult6 des Sciences, I l e du Saulcy, F-57045 Metz Cedex 1 , France

"~Bgedur-Pkchiney, Centre de Recherche e t Developpement,

~ . ~ . 2 7 , F-38340 Voreppe, France

Abstiacr: Al-Li alloys in uncecrystallized conditions present a song texture which influences considerably their mechanical behavior. The Vemr Method has been chosen to analyse the t e m e of Al-Li alloys produced by CEGEDUR-PECHINEY. We first explain why we chose an analysis with a single incomplete {220) pole figure in reflection (maximal tilt angle = 80 degrees). The spectrum of the texture vector is drawn after re-numbering the components to make the otthotropy obvious. We then present some c h a r a c t ~ c textures measured during the schedule of thermomechanical treatment applied to an Al-Li alloy in order to obtain sheets.

Al-Li alloys in unrenystallized conditions present a strong mmue which influences considerably their mechanical behavior. So, for such alloys, the texture is an important parameter. It allows at once to foresee the properties of the alloy and, when measured all along the thermomechdcal processing, to control and adjust the treatments in order to meet the requirement for high and isotropic mechanical popetties.

The Vector Metbod has been chosen to analyse the texture of the AI-Li alloys pmluced by CEGEDUR-PECHINEY. That choice results from two considerations:

the texture of the alloys being strong, the Vector Method 11.21

-

-

considered by the metallurgists as ideal orientation figures. However it is imponant to know the density of desorientation around the ideal orientation. Moreover many models of elastic and plastic behavior use a small number of ideal orientations (100 at the most), the self-consistent model in particular 131.

the Vector Method allows a good analysis with a single incomplete pole figure in r e f l e c t i o n w a t a collection much more easy and saves a lot of recording t h e . The technique using complete pole figures in reflection-transmission is long. It requires careful handling and the linking is often bad because it is made on a few rings only, on which the intensity is not necessarily high. Our studies of residual figures show that very often the residue is maximum in the Linking area.

3. CHOICE OF THE FIGKREL

With Al-Li alloys only 3 figures diffract well (1 11)(100%), {200)(47%), {220)(22%). So we have measured those 3 figures on a particularly well textured sample. We chose an AI-Li 2091 sample, rough from hot-rolling, and, to perfect the analysis, we merely sntdied the surface texture.

The collection and treatment grid is the same for all the measurements and analyses we have performed : 2.5 degrees in tilt, 5. degrees in azimuth. All the figures are measured in reflection, up to the maximum tilt of 80 degrees. Our aim was to obtain a good estimate of the texture with minimum experimental data

-

Plate I shows the 3 pole figures thus obtained.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987372

C3-622 JOURNAL D E PHYSIQUE

4. ANALYSIS POSSIBILITIES AND RESULTS

The (200) pole figure is not suitable since its M.P.D.S. covers the whole figure. On the contrary. the M.P.D.S. of figures {I 11) and (220)

-

* the experimental pole figure used for the analysis

* the spectrum of the texture vector found

* the recalculated pole figures used

-

The texture veaor can be represented in m o different ways

-either by drawing the usual O.D.F. in sections (intensity curves in the Euler space) -or, mom simply, with the spectnun of the texture vector.

We have preferred the second solution because it is simple and more direct. One representation possible

-

However, a beaec representation consists in making the DL,DT frame ( the macroscopic frame linked to the sample) obvious and in making the texture oathotropy -if any- also obvious. To do that, the texture components are numbered in a different way taking into account the following propelties :

1- Two components symmetrical I DT have for parameters (Y,55) and (-Y,k,c).

2- Two components symmetrical I DL have for parameters (Y,h,() and (Y,h,2n<).

3- Two components symmetrical I ON have for parameters (Y,h,() and (-Y,X,n+().

Those 3 properties allow to draw the components of the textwe vector in 4 quadrants. If the figure is otthocropic, the 4 images are symmetrical. So indices of symmetry and otthorcopy can easily be giva.The deviations from the otthceopy are a good test to find a suitable thermomechanical ueaunent.

The best results were obtained with pole figure (220). That may seem strange when we read the intensities of the planes on the A.S.T.M. card. The reasonis that the { 11 1) figures have their maximum intensity on the border, outside the area analysed. So the central information is not as good. On the contrary, figure (220) has all its strong spots in the central analysed area.

The residue is 9.00 for 30 itemtions. The comparison between the experimental figures aad the recalculated figures shows that the iso-intensity curves superpose exactly and that the maxima are well located and of nearly the same intensity.

To check the accuracy of the analysis, we also recalculated the figures that have not been used for the analysis. The recalculated figures are compared with the experimental figures and we verify that they coincide perfectly.

The analysis with { 11 1 )+{220} is less good than the analysis with ( 1 1 1 ) or (220) alone. That result shows clearly that increasing the number of figures taken into account for the d y s i s does not necessarily increase the quality of the analysis. especially if incomplete pole figures are used. Here. { 11 1) being of less good quality, lessens the quality of the analysis.

Fatberine the c o r n o m

The texture components, 2016 of them, are gathered in a small number of strong components in several ways. The easiest way consists in sotting the components according to their intensities and in considering, for a given application, only the components with an intensity higher than a given one. Then, for each component chosen, the volume of the sample ha* the corresponding orientation is calculated. Another way, rq&ing a more complicated program. c6nsias ingathering d e components round strong components by f ithe w l e of the desorientation cone. Thus we can find the oart of the material for which the orientation e

is in&e in&& gidg with dg varying at will. ^"

The typical thermomechanical processing used for thinner sheets is shown on figure 2.

Five sam les have been considered (1 to 5). The first sample was used to choose the figure to be analysed ($4 and $S).Then, only the (220) pole figures were made. The comparison between the pole figures is done with the experimental figures normed by means of the norm of vector Y calculated, since the p d a l norm cannot take into account the missing part which varies from one figure to another. Plate 3 shows the other 4 figws (samples 2 to 5). The f i p s show that the sample, a hot-rolled sheet, presents quite a strong rexnue, which becomes even stronger when the sample is annealed in an air-furnace. The effect on the texture of the subsequent cold-rolling is small. But a wament in a salt bath weakens the texture whereas a tteatment in an air furnace saengthens it considerably.

The figures obtained all show some very strong ideal orientations of the (01 l)<uvw> type. The results of the quantitative analysis are summarized in table 1. All the unrecrystallized samples obviously show the same svong texture.

results of the quantitative analysis

9.2 The texture ggadient

C3-624 JOURNAL DE PHYSIQUE

The pole figures taken as a whole, meiswed on various alloys and various products (2091 38 mm sheet annealed for 12 hours at 135%. 8090 13 mm sheet ) show a v e v strong t e r n gradient in the sheet thickness. More precisely, the analysis shows

* for a similar fibering, a texture close to that of the usual Aluminium alloys, but monger. A good description of that texture is given by the classical strong components of rolling

- { 1 lo)< 1 12> brass component predominant at the core and on the surface

-

-

* in the case of 8091, an intensity gradient of the brass component much weaker for the thin sheets than for the thicker sheets (13 mm or 38 mm).

Those analyses have been correlated with the mechanical propetties noted on the same samples. They are the basis for the modelization of mechanical propdes.

From that study we have been able to draw too useful conclusions :

1- on the method itself, The Vector Method is perfectly suitable for the study of strongly textured materials such as A1-Li alloys. A single incomplete pole figure allows to calculate the texture with a good approximation. The components have been gathered according to the metallurgktd notation {hkl}<uvw> and the volume of each component has been calculated.

2- on the correlations between the various anisotro~ic nrooerties of Al-Li rolled ^sheets. The

quantification of the various anisotropic properties, together with that of the nystallographic and morphological temres, allows to understand better

-

As a conclusion, we can say that obvious relations between the texture and the mechanical properties should result in improving the models and the conditions of the thermomechanical treatments.

BIBLIOGRAPHY

Ill D. RUER. Thesis. METZ University. Fratlee n / A. VADON. Thesis. M E I Z University. France

131P. LIPINSKI. M. BERVEILLER. A. HIHI, Ph. MEYER, Ph. JEANMART

Effect of crystallograhic and morphological textures on the anisotropy of mechanical properties of _{- .} Al-Li alloys. In this volume. -

141 D. RUER, A. VADON, R. BAR0

Advances in X-Ray Analysis. DETJVER University. Vol23 p 349-360

JOURNAL DE PHYSIQUE