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EBSD Analysis of Friction Stir Welded 7136-T76Aluminum Alloy 

 ARTICLE  in  DIFFUSION AND DEFECT DATA PT.B: SOLID STATE PHENOMENA · JUNE 2013

DOI: 10.4028/www.scientific.net/SSP.203-204.258

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EBSD Analysis of Friction Stir Welded 7136-T76 Aluminum Alloy

KALEMBA Izabela 1,a, MUSZKA Krzysztof 1,b,  WROBEL Miroslaw 1,c

DMEK Sta!islaw 1,", #AMIL$O% &arter ',e 1 A(# U!i)ersity of Scie!ce a!" $ec*!olo+y, Al Mic-iewicza ./, ./0/2 Kra-ow, 3ola!"4

'Mia5i U!i)ersity, O6for", O*io, USAa-ale5ba7a+*e"89l, b58sz-a7a+*e"89l, c5wrobel7a+*e"89l, "+5"y5e-7cyf0-re"89l,

e*a5iltbc758o*ioe"8

Keywords :SW, al85i!85 alloy, EBSD, te6t8re 

Abstract. This research addresses the EBSD analysis of friction stir welded 7136-T76 aluminum

alloy. The objecties of this study were to ealuate the !rain si"e and their sha#e$ character of !rain

 boundaries in the stirred and thermo-mechanically affected "ones$ both on the adancin! and

retreatin! side as well as to inesti!ate chan!es in the crystallo!ra#hic te%ture. &esults of te%ture

analysis indicate the com#le%ity of the friction stir weldin! #rocess. The te%ture !radually wea'enson moin! from the thermo-mechanically affected "one toward the weld center. The stirred "one is

characteri"ed by ery wea' te%ture and is dominated by hi!h an!le boundaries. (n the other hand$

the thermo-mechanically affected "one e%hibits a hi!h fre)uency of low an!le boundaries.

Introduction

*riction stir weldin! +*S, has become a #o#ular joinin! technolo!y used in many branches of

the manufacturin! industry. *S,$ which was inented by The ,eldin! nstitute in /ambrid!e$ is a

solid-state joinin! #rocess that achiees hi!h-)uality$ sound welds with !ood mechanical #ro#erties.

The #rocess is widely used for weldin! li!ht metals$ es#ecially those which are difficult to weld by

traditional fusion weldin!. 0dditionally$ the #rocess offers numerous enironmental adanta!es andcost-reducin! benefits 1$2.

*S, constitutes a thermal and deformation #rocess. Durin! friction stir weldin! material is

mi%ed by a rotatin! #in and under!oes intensie #lastic deformation. t is also heated by friction

 between the shoulder and the welded #lates surface. This induces si!nificant microstructural

chan!es in the weld area and results in the deelo#ment of distinct microstructural "ones4 stirred

"one +S5$ thermo-mechanically affected "one +T05 and heat affected "one +05 1-3. t is

common 'nowled!e that the weld microstructure influences its mechanical #ro#erties. Therefore$

'nowled!e re!ardin! !rain si"e$ state of #reci#itates$ crystallo!ra#hic te%ture and character of !rain

 boundaries is im#ortant. The studies of the te%ture deelo#ment in friction stir welded aluminum

alloys are not numerous. (nly a few inesti!ations dealt with te%ture deelo#ment durin! *S,.

The inesti!ations were carried out on heat-treatable 2%%% and 6%%% aluminum alloys 8$9 and onnon heat-treatable 9%%% series 6. This research addresses the Electron Bac'scattered Diffraction

+EBSD analysis of friction stir welded a!e-hardenable aluminum alloy of 7%%% series.  

Experimental details

The material used in this research was a 7136-T7691 aluminum alloy su##lied by :niersal

0lloy /or#oration. The alloyin! elements of this alloy are followin!4 5n +7.;8<$ ! +1.;;<$ /u

+1.;8<$ 5r +=.18< and also *e$ Si$ Ti$ n$ /r and >i. The 6.39 mm thic' #lates of the alloys were

hot e%truded. Thou!h the alloy was hot e%truded the stron! deformation te%ture was retained due to

the #resence of "irconium which ham#ers the recrystalli"ation #rocess. Thus the te%ture of the

welded #lates was ty#ical for cold rolled metals with a face-centered cubic crystal structure whichdeforms only by sli# +*i!.1. The #lates were friction stir welded in a butt joint confi!uration at the

Edison ,eldin! nstitute in /olumbus$ :S0. The #rocess was carried out at a tool rotation s#eed of

29= r#m and weldin! elocity of 2.1 mm?s with a down-force of 21.7 '> a##lied to the tool. The

Solid State Phenomena Vols. 203-204 (2013) pp 258-261Online available since 2013/Jun/05 at www.scientific.net © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/SSP.203-204.258

 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 149.156.112.56-05/06/13,16:18:09)

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direction of joinin! was #arallel to the e%trusion direction. The *S, tool consisted of a cone%-

scrolled shoulder 17.@ in diameter and a threaded truncated cone #in with dimensions4 u##er

diameter - 1=.3 mm$ lower diameter - 7.7 mm and the len!th - 6.1 mm. 0 schematic of the *S, and

tool desi!n are shown in *i!.2.

*i!. 1. +111 #ole fi!ures for base

material.

*i!. 2. a 0 schematic of the *S, #rocess and tool desi!nA

+ED - e%trusion directionA b Tool.

icrostructure and te%ture characteri"ation was #erformed by means of Electron Bac'scaterred

Diffraction. EBSD #atterns were obtained on the *E SE +*E ns#ect * o#erated at 2= 'C onthe cross-section #er#endicular to the weld direction. The EBSD #atterns were measured with a ste#

of =.9 m and coered the area of 963 m F 2@8 m. The inesti!ated surface was mechanically

!round and electro#olished in a solution of nitric acid?methanol +142 at 12 C and a tem#erature of -

3=G/. The electro#olishin! time was 6= seconds. The weldment re!ions of #articular interest were

the stirred and thermomechanically affected "ones as well as the boundary between them$ both on

the adancin! and retreatin! sides. The HI /hannel 9 software was used for the analysis.

Results and discussion

The *S, weld was fairly homo!eneous and free of defects li'e discontinuities$ crac'in!$ #orosity

etc.. 0 macrostructure of the weld cross-section is shown in the *i!. 3a. *i!ure 3b #resentsorientation ima!e ma#s of tested areas$ which are mar'ed in *i!. 3a.

*i!. 3. a acro!ra#h of cross-section of the *S, weld$ b orientation ima!e ma#s of boundaries

T05?S5 on adancin! and retreatin! sides. The color trian!le shows #oles ali!ned with the

normal direction of the #late.

Solid State Phenomena Vols. 203-204 259

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The ma#s com#rise areas between the stirred "one and the thermo-mechanically affected "one$

res#ectiely on the adancin! +0S and retreatin! sides +&S. The ma#s show indiidual !rains$

which are colored accordin! to their crystallo!ra#hic orientation relatie to the normal direction.

&e!ions of the same crystal orientation are mar'ed with an uni)ue color accordin! to the orientation

code trian!le.

The stirred "one and thermo-mechanically affected "ones differ in si"e and sha#e of !rains +*i!.3b. This is caused by different e%tent of #lastic deformation and tem#erature increase in these

re!ions occurrin! durin! *S,. The stirred "one is characteri"ed by a fine-!rained structure

resultin! #resumably from dynamic recrystallisation occurrin! durin! the *S, #rocess. *i!ure 8

shows !rain si"e distribution in the S5. The diameter

was about 2-8 m. (n the other hand$ the T05

consists of lar!er$ elon!ated !rains$ es#ecially on the

adancin! side. The !rain si"e in the T05 was

ealuated based on orientation ma#s. The sha#e of

!rains de#ends on the location in relation to the weld

center. (n the retreatin! side !rains are a##ro%imately

e)uia%ed. oweer$ on the adancin! side !rains arestron!ly elon!ated in the direction #er#endicular to the

 #late surface. The as#ect ratio for such !rains aera!es

about 3. The close #ro%imity to the S5 is characteri"ed

 by lar!er !rains +on the 0S !rain si"e is 3=-8= m and

as#ect ratio J 3. The elon!ated !rains indicate #artial

recrystalli"ation of this re!ion.

*i!. 9. +111 #ole fi!ures for #articular re!ions of joint4 a adancin! sideA b retreatin! side.

n order to accurately analyse chan!es in te%ture the EBSD was measured in the 6 characteristic

re!ions4 T05$ boundary T05?S5 and S5 on both weld sides. The crystallo!ra#hic te%ture was

characteri"ed in detail by means of #ole fi!ures. *i!ure 9 dis#lays +111 #ole fi!ures for the

 #articular re!ions. Kole fi!ures reeal chan!es in te%ture on the cross-section of *S, weld. The

te%ture wea'ens on moin! from the T05 toward the weld center +both on the adancin! and

retreatin! sides. The area of the S5 is characteri"ed by ery wea' te%ture +ma% intensity does not

e%ceed 3.1 com#arin! to the base material +*i!.1$ whereas in the T05 the si!nificantly stron!er

te%ture was obsered. *or this re!ion ma%. intensity aera!es @.8 on the adancin! side and 9.8 onthe retreatin! side. The te%ture transition occurs on the boundary T05?S5. The chan!es are

located in the ery narrow area. The #ronounced ariation of !rain si"e also occurs in this area. The

 #ole fi!ures calculated from EBSD inesti!ations are fully consistent with the authorsL earlier

studies 7$ where te%ture characteri"ation was #erformed by M-ray diffraction.

The difference in te%ture intensity is obsered on the adancin! and retreatin! sides. The te%ture

is wea'er on the &S com#ared to the 0S. The chan!e in te%ture as well as the ariation of !rain si"e

on the &S occurs on the wider area. The differences between the sides are also isible on orientation

ma#s +*i!. 3b. The T05?S5 boundary on the 0S is shar# and well-defined$ but on the &S it is

more diffuse.

The EBSD analysis also #ermitted the analysis of the !rain boundary character. *i!ure 6 shows

histo!rams of !rain boundary misorientation in s#ecific "ones +T05 and S5 to!ether with the

acHen"ie #lot @ +characteri"in! misorientation an!le distribution for a randomly te%tured cubic

 #olycrystal. The tested "ones differ in !rain boundary misorientation. The T05 is dominated by

low an!le boundaries. Distributions of boundary misorientation are similar on the 0S and the &S.

*i!. 8. rain si"e distribution in the S5.

260 Applied Crystallography XXII

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oweer$ the adancin! side +*i!. 6a e%hibits a hi!her fre)uency of low an!le boundaries +N1=G$

 but the retreatin! side +*i!. 6c was characteri"ed by a hi!her #ro#ortion of low-mid an!le +2-2=G

 boundaries. n the T05 distributions of boundary misorientation are not corres#ond to the

acHen"ie #lot$ su!!estin! that full recrystallisation has not occurred in the "one. The S5 +*i!. 6b

has hi!h fre)uency of hi!h an!le boundaries +22-6=G. The distribution of boundary misorientation

in this case mimics the course of the acHen"ie #lot. This su!!ests that the !rains in the S5 e%hibitnearly random crystallo!ra#hic orientation. Dynamic recrystallisation ta'es #lace in this "one.

*i!. 6. isto!rams of boundary misorientation distributions for a the T05 on the adancin! sideA

 b the S5A c the T05 on the retreatin! side.

Summary

The stirred "one and thermo-mechanically affected "one differ in si"e and sha#e of !rains and

 boundary misorientation distributions. The S5 is characteri"ed by fine-!rained structure and is

dominated by hi!h an!le boundaries. The T05 e%hibits lar!er$ elon!ated !rains and a hi!h

fre)uency of low an!le boundaries.

Te%ture e%amination #roed the com#le%ity of the *S, #rocess. The EBSD reealed ery wea'

te%ture in the stirred "one. This was confirmed by the distribution of boundary misorientation$

which corres#onded to the acHen"ie #lot.

The *S, microstructure deelo#ment was clearly asymmetric. This manifests itself throu!h

differences in !rains and te%ture on the adancin! and retreatin! sides. The adancin! side is

characteri"ed by the well-defined boundary between T05 and S5 and hi!her intensity of #ole

fi!ures com#ared to the retreatin! side.

Acknowledgements

The authors would li'e to than' the Kolish inistry of Science and i!her Education +Kroject

 >o. 11.11.11=.183 for their su##ort of this research.

References

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+2=1=$ #. 1;626  >.T. Humbhar$ S.H. Sahoo$ . Samajdar$ .H. Dey and H. Bhanumurthy4 ater. Desi!n$ Col.

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Applied Crystallography XXII 

10.4028/www.scientific.net/SSP.203-204 

EBSD Analysis of Friction Stir Welded 7136-T76 Aluminum Alloy 

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