The effect of artificial aging on the tensile properties of alclad 24S-T and 24S-T aluminum alloy

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Title:
The effect of artificial aging on the tensile properties of alclad 24S-T and 24S-T aluminum alloy
Series Title:
NACA WR
Alternate Title:
NACA wartime reports
Physical Description:
6, 11 p. : ill. ; 28 cm.
Language:
English
Creator:
Kotanchik, Joseph N
Woods, Walter
Zender, George W
Langley Aeronautical Laboratory
United States -- National Advisory Committee for Aeronautics
Publisher:
Langley Memorial Aeronautical Laboratory
Place of Publication:
Langley Field, VA
Publication Date:

Subjects

Subjects / Keywords:
Aluminum alloys -- Testing   ( lcsh )
Aerodynamics -- Research   ( lcsh )
Airplanes -- Structure -- Research   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Summary:
Summary: An experimental study was made to determine the effect of artificial aging on the tensile properties of alclad 24S-T and 24S-T aluminum-alloy sheet material. The results of the tests show that certain combinations of aging time and temperature cause a marked increase in the yield strength and a small increase in the ultimate strength; these increases are accompanied by a very large decrease in elongation. A curve is presented that shows the maximum yield strengths that can be obtained by aging this material at various combinations of time and temperature. The higher values of yield stress are obtained in material aged at relatively longer times and lower temperatures.
Bibliography:
Includes bibliographic reference (p. 6).
Statement of Responsibility:
by Joseph N. Kotanchik, Walter Woods, and George W. Zender.
General Note:
"Originally issued August 1943 as Restricted Bulletin 3H23."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003804957
oclc - 123902924
System ID:
AA00009442:00001


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RBN o. 3H23





NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS


WA RTIMEI REPORT

ORIGINALLY ISSUED
August 1943 as
Restricted Bulletin 3H23


THE EFFECT OF ARTIFICIAL AGING ON THE

TwSILE PROPERTIES OF ALCLAD 24S-T

AND 24S-T ALUMINUM ALLOY


By Joseph N. Kotanchik, Walter
George W. Zender


Langley Memorial Aeronautical
Langley Field, Va.


Woods, and



Laboratory


WASHINGTON

NACA WARTIME REPORTS are reprints of papers originally Issued to provide rapid distribution of
, advance research results to an authorized group requiring them for the war effort. They were pre-
Vonlisly held under a security status but are now unclassified. Some of these reports were not tech-
.alafly edited. All have been reproduced without change in order to expedite general distribution.


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H).TIONAL ADVISORY OO) WITT3E 'FR A3SPOl.\rTICS



P~STFRICT3D EUiLLETIII



THE KFF-CT OF ..PTIFICIA.L .'1.!Ii'3 C" T:E

TSI:S1LES PP ROPFTTIJ: OF ".LCLD 24S-T

:'rI 24S-'" A.L!TI'rF' .!LLOY

B,- Joseph U'. K:ot.,nc:.ik, Waiter Toods,

and 'ecr;e '. en6rer


S T 7, l.'. R 'f


An experimrr.ntal stud:., .'*;. made to deter'.i inC: the effect of arti-
ficial E:ir'g on the tSnsiie properties f) a!l.d 24S-T and 24S-T
alLumiinum-alloy- sheet ,nmterial. 'he rI-cs'lts of the tests show that
certain combinijtionts of agiin: timne and temperal-tiur cause marked
increase int the ;,,leld str..nr-th and ? :msli in.?rease in the ultimate
strength; these in-rertses are accomi[anied U;; a very large decrease
in elongation.

A curve is presented t!h't shows t}.e ini-Xl.nflr yield Strenrths that
can be cbtain.d by rginp: thi.: .u.'terial at v\rious ccTLubiltions of time
and temper..ture. The higher valu-s oj ;,lieid stress are obt.in.ed in
mat *rinl1 aged at rjl.ativel/ ioner.r ti;-es and lower temp:rat:.rars.


I Tj POD'T; GT I!


In the di-sii.n of Fa airplgne, vei-ht -on.trnl is a leading problem.
Ever .,' part of the irm!auie must '..3 oj design-d or :e). o3ted as to elimi-
nato uirecosF -ry vei rt. O".(: of tthe .io'-t i... ti t"it items that cantri-
Lnte to toe -ros- w-'-ig'.t of t'he aiirl.-r.e is the strLutisre. For this
reason, thi air.-lene sti-'iture is :-1i:.:in:., ..iost critically for climina-
tion of' unie-c,"-: ry vrweli.. The .-.rntinri n, :i e a.,in :n.; in methods of
analysis -.re ar important factor for rlnviinf -L'.-out reduction in weight
of The sirplanr, bit thL airplane dr-zi,'n.-; ard bui.ier must, in addition,
utilize oth-r methods for combatinc: th tren'i tcvwrd Ircreased struc-
turel weight. One of ti m.ist dir-'?t m t:-C's is to improve the strength
prop-rties of mattriPis already: availa '- or in c'.irrent production.
This method has the v.ry:' important advantag,- that it -:n be put into use
with a minimum of dulay and inturruption to established methods of
production.












A. number of aircraftt companies ara now considering the use of 24S-T
alu Lnuln eliooy of which thu strength properties have, been improved by
artificial st-ing. This report presents the result: of tensile tests on
alclad 24S-T nnd 24S-T aluminum-alloy sheet material that has been artifi-
cil.lly aged at various cjmnhinations of temperature and time.


A.TSRfT.L FOR ARTIFICIALLY ACED TEST S?ECILSIiS


As th- purpose io these tests is to present the results that can be
obtair.ed bv artifiicirl ing of corriercially obtainabli. material, specimens,
of the. dinenic.ns s!honv in fi'ijre 1, wore rit from sheets selected from
alcl.d 2-S-T and 24S-T aluuainin alloy a, received from the menufacturor.
The stretchin-, and rolling operations prrformx.d on alualir.num r.lloy at the
mills are a2proximntetly' c qivalen.t t. tl:- cold wocric done in giving the sheet
a perrnanRnt elonr.-tinn -.f L percent (reference 1). The extent to which
the strcetFth rroporti.,i of 24-3-T al',-linn. alloy, .:Pn 'e improved by Arti-
ficir.1 in;- is d Fj'pe)d..'rr i..n..: t'h- inmo nt of cold *:ork .perfor,:ed on the
material prior to th... :gin proo ,'r (rcf'Lrrinze 1). It -is therefore neces-
sory th.it the r n ri-.l be of un'iform:n qucli-y rP reg-,rds th'e amount of cold
work p-rformed prior to rfinr- in ori.er that consistent results De obtained
fr-.m thc artificil 'ging..

For th.? t 'ts reported .-rci.i, the cutting of th.e 24S-T and the
elelad 24SE- specine:ri rj.i sinr,'l sheets 'i' itc h '. a11L-terial assured
unif- rmniy of thie zpec-i;i:.,nns as reZ rds the de-ree' of cold work performed
upon them. That the mnsterisl rwa uniform os re.grd'f cold work is in-
di-.- t--d ;by the conr istent trendc: cstbclished by t'hL test data in figures
2 Lnd 3. Th- exten.siv- adoption of the %rtlfici.l Eging process would
nece'ssi r'te thrt clocr: rcr il ti.on b- mair.tained or. the uniformity of and
thb. nmc int of 1ld v.Jrk p- .-rforicod on th:. slxuininr. alloy.


TEST SrJ;"I!.'S

The t..rt sprccim.:ns w:;trc ;tamicd iro. single -;c,-ts of 0.064-inch
alclr.d '-;S-T and 2'1S-T .el n. n.i .n alloy b:y i.:I.ns of a die. In the test
portion of t--- spi i,:,:,, ti,.: sh.:ared ed .-es weru nar,:fully hand filed to
remove the: li-.tl t .rL..d c-~ i.:ft b.- Ihe. stamiping die. One specimen
was mode for each combine ntiton of tiT oaid ,temi.erature investigated.

Artificial rgin': of the s .eci:ens was .;-rformed in an electrically
he.'ted air furnpce, -;nd tlhe spocimerns were cooled in air at rc.on temppra-
ture. Th 3 test sp'..-cimns i"ure p"lc.d in th,! fI'.rnale* which was at
th' d.-sircd temperLture, rnd the Lging time wr-s taken as the entire











period during which eFch sp-cimen was in the furnace. The
results are therefore representative of th-a values obtain-ed
vith material that is artificially aged in th.e same manner.

The data for th2 tensile stress-strain curve were obtained for
each specimen to a value of strain beyond tlat at the 0.2-percent-
offset yild strength. Strains wer.e measured by two Tuckerman optical
strain gages of 2-inch gage length attached to opposite sides of the
test specimen. The olonga'tion at failure was determined by measuring,
after failure, th. increase in length of tue initial 2-inch gage length
of the test spjci.ien to th r.narest J.01 inch.


TfST RESULTS A':nD DIScEISSIO!:


The results of the tensile tests on the artificislly oged test
spuci.ians are given in figCres 2 to 5.

Figure. 2 cho'.'s the variation i.i t'i., ultinct strength, the yield
strength, and the olonr- .:io of' ilrlcd 24S-T mot.rial that is sub-
jected to Ertificiel :-ging for p riods of 2, 4, 0, 7, and 10 hours at
temperatures that vw.rr fro.n !00 to 5300 F.. The important information
contained in this figure is that a substantial increase in field strength
-nd decrease in elonr-.tion occur in t,,e .iEteri.l v:'rn agcd in the
temperature rangp of' 3400 t: 400 F. In this tempr-r'ture ranpe, a
small increase in the ultimate strernth nf the mastri-.l also occurs.

The most desirr'cl result obtained front artificial aging is the
large increase ir yield strength. .Alth:,u h' t-is report presents
only the results of tensile tests, some compression tests 'inve been per-
foraed on arti fcii'lll sged ms:terial and thrse tests indicated that
the compressive yield stren.:th was increas.-d in jesrantiall., the same
way as the t-,sile y;iild strength. Bly takit.n into account the increase
in yi3id strength, the airplane decignr can cff',ft substantial reduc-
tions of weight in certain parts of the airplanee For example, the
full increase in yield strength can be ui lized in the design of com-
pression members so proportioned -ind supported t-hat they will not fail
by instability before the compressiv. yield strength is reached. In
the case of t-nsi n manbers, only n p'rt of -he' increase in yield
strength can b. utilized 1ind.r pr,-.crt dsi-n rquiirments b-cause these
requirements specify : a definite ratio of allowAble yield stress to
ultimate stress, and the altimace strength of the artificially aged
material is not increased in the sare proportion as is the yield strength.

The increase in yield strength ir accompanied by a change in the
elongation in 2 inches from rbouit 13 percent to about 6 percent. This
decreas.- in elon-ation will undoubtedly add to the,, difficulty of












forming the material during fabrication. In many cases, however, the
added Jifficultt: can be avoided by completing the forming operations
prior to artificial aging.

Figure 2 also shows that for any aging time the temperature must
be maintained within a ranre of Lo?. of the eptirarum value in order
that the b-st increa.r of yield .tr.ngth nay be obtained. This
standard of ter.p-'erture maint,.anance is readily cttains.bl? with modern
hrat-tr'-L t ng eqipma.nt.

Th.e vurittin in yield ztrncgth of alclad 24S-T memorial that is
subjected to artif'real aging at corstant tenmperatt'res for var..yng
period of time i: s'owwn i-. f:-ure 3. i' w.ll Le noted on this figure
that for values of tc-mo-.rof.iurc above 3,'0" F there is on nfiug time
which w 11 r- ul- in a lIAXi.a"'m i.cra5ssE ",I *lld stre.th. Foor 'ing
time: 1:ss th'.n cr -rea:tcr th.'-n t.h c'Li -ri'r t'i lower v ILIrS of :-ield
sTreS v.1 11 be, obt:inei. /t tmi" rL t'.ir s n in cx?: s; of 4.'50 i. th.e
aging tir.3 'ncrnver v. rv cr'tical. h:' d&ng-r oi r.d i asin- or over-
aginf of tht mct ri?. v:.'t t. ,, sequent iar;e iec:'r-a~ ni yi eld strength
is q'lit? s rinus. jor t..ic r'.Lr.a: iginrf t. er. F '. :' -s ir. 0xc' -s of
4250 F ere not f:o-sibl- fr ;ircductecn r'h..rc th ci1ru 'ta-r wf t-. work
is chLan ing sri-. .*'nc'r t. it is .ifficult tc. de.ter.nin.: '*,.:- .,xrct tine 't
whien tea material r s-'--es t, a'ins- tqj.p-'rature. At sa9ln te;aperjaturcs
of 40C' F r.d low.r, t-:.o l:".o-tent iovnntere3 exist; n1I 'L.;, '.i er
absolute vlun s nf yield s .r.enth c:.n e obht--:in)d ard th ;rE is a consider-
able range of tia', Qt wr!.i. r'L ri ng may. b' c.r.ni ina-J vl1+ho't eppraciable
loss of yil1d strrrzn:!t by, reason :f small imo.'ntF of 'ndrG.'Tgr.g or
over:,inp.

Figure 4 I.re--.n*ts n curv:s of yiold-strength .raxinmums for various
c-Imbinations of tl:ne san tm! :rstura. Viithin the rEnrce of values
covered by this invt +i.etnon, this curve shows that, as aginb tempera-
ture dearei.ss, tno aginr time required for o- st yi-ld strength increases.
TVi oure !-iso si;ov..: t'"t th.j hri r-.Tr values of vield strength are obtained
at the cm.uinstions .if low':r temburrl1turus Lrd longer aging times shown
on this figure.

F'iure 5 showed the variation of the tpnsile properties of 24S-T
with te.n.crature .c r a constant aping time of 2 hours. 'Then figure 5
is conl..red v.lth figu!e 2, it is ovi.2ent that 243-T material responds
to ar'ificisl r'ging 5n moinnnri simiizr to nlclsd 2-4-2.

The tert spec:imins which were ar-ed for 6 hours at various temper-
atures gre sho.'.m aft*.r fracture in figure 6. The liange in clonrgtion
is clearly scan in th r.'~al l-n:,'hs of th' snecmr.ens. The chorectpr-
istic fr-zt':ret th:t ccctrrud -t the vLi:ioJs te mpervtures for e:ich aging
tim:e- re al-o sho'"n. A.t t~Lm-nrsturc. uelow -the ra;i.e of critizsl aging
tem"perat-res, .s in the 1030 F eno 2u00 F srecuiens on figure 6, the











fracture vwas normal to the direction of the load but was inclined
at 450 to the tLicknezs cf the material. In and beyond the region
of terperatures corr,'sroind ng co the gr Pttest decrease of elongation,
temperatures of 370 F and higher, the fracture changed to one that was
inclined at 300 to the width of the specimen. The surface of the
fracture vas relatively rmooti for the mat-rial aged below the critical
temperatures but it b.::came "er;' rough and irregular in the specimens
aged at the hiIiher terap.eratuires. In the transition range of tempera-
tures, the fracture was pertly of both types us shown by the specim.-ns
marked 300 F and 3530 F in figure 6.


STR3,SS-STPAIN C'.RV 'S


The tensile stress-strain curves for the specimens tested are
shown in figures 7 to 12. Th= 3O.-per.ent-offset field d strength is
indicated on exch ztr-!ss-strain curve by a short intercept line. These
yield strengths were used in preparing figures 2 to 5. The stress-
strain curves show that the 0.oduil~s of el.ksticity is substIntially the
sa:ae for the combineticns of terip.ert;,re andC time innludd in this in-
vestigatinn. It cn Le cbscrvAd, how;.'vr, thut s '.he aging tempera-
ture incr::ases tihe initial rairt of the stress-straili curve tends to de-
velop ,nor, curv'tuire, which indic'ites a tr?nd toward reduction of the
proportional li:it at the higher ?.finr temperatures.


COTCLUIS IO'S


Artificial aging of alclad 24S-T alu;,inu:a-clloy sheet material in
the es-received condition produces a zub'tantiai increase in yield
strength, a sir.ll increase ir. ultihaste stre-'gth, 3nd a large decrease in
elongation.

The artifi-.ial-aiin,; process prodries- esver.tialiy the ceme effect
on 243-T shc-.t latoriail .:is or: alcld 24S-T l.eet in.terial.

At any riven temp raturc there icn in opti'um value of aging time re-
quired to obtain m',ximu.un ,elue :. yield str.ngth. In general, the aging
tim.' required to achieve maxim-u yield stretirti bcoIrs less as the
temperature increases.

The rengrc of aginC t,.-iipez+urcs for which t, substantial increase in
th? yield strength is noted is mall.



Langley RMamorial Arronautical Laboratory,
National Advisory Committee for Aeronautics,
LanGley Field, Va.












REFERENCE

1. MEozley, Paul P. Elevated Temperature Aging of 245 Aluminum Alloy.
Paper presented at the eleventh annual meeting of the Inst. Aero.
Sci., Jan. 1943.








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UNIVERSITY OF FLORIDA
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3 1262 081061V47 8


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UNIVERSITY OF FLORIDA
DOCUMENTS DEPARTMENT
120 MARSTON SCIENCE LIBRARY
P.O. BOX 117011
GAINESVILLE, FL 32611-7011 USA


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