. .

.. .
,,
------- ,.4-,

[ ,,
...

1.

.,,.

. ,,-

D~PbtLUMIN , TTS

USES.

BY R. Beck.
.-11
From 11
Zeit schrift Iur
?,[eta
11land-e,
~ .jpri1, 1924.

October, 1924.

1
-----

-..

llllllllllllllflmiM[llllllllllllll~
~

31176014410303._;
_--.
m ..-
-------NATIONAL ADVISGRY CGMMITTZE FOR AERONAUTICS.

_
..

that duralumin is a,~erman discovoxIy and t!ncrcfoue a present of

German sciencific research to tilemetal industries of all civilized
countries.

The contraiy opinion is occasionally ri~etin tinenews-

papers and.perio?.icals of other ccuntries,

Such ptatements are not

necessarily malicious, but should, nevertheless, n.ot remain unchal1 enged.

For example, the En@i sh periodical- llTheEngineer$ IIof

December 7, 1923, contained the following footil~te to the translation

of a German article on Cluralumin:
o~uralumi.n i-n t-he

Ge

man

o~igina3. fmm

which this article has

been p~epared, but, as this word represents a proprietary article in

this Cou-ntryand as the Geman

alloy co rrespond-ing to it is said.to

be Clefinitely clifferent from the British-made material, we pref m

to

!?-sethe expression .
aluminiurn alloy 1
Thus it appears that the editor prefers to employ the term
!!duralurfl~n[l
only fo T ~~ealloy

CI f

E:nglish

origin a-ridto

desig-nate the

c.erman alloy as li
aluiliniuclalloy. II I here wish to comect

the error

The Yngineerll by statin~ that the word ltduraluminll.

of the editor of II
.
* From 1
zeitschrift fur Metallkund-e j:
April., 1924, pp. l~z-lzi

&
,.,

U.A.C.A.
is

also

Technical Memorandum No. %34

of German origin.

It :!as
patented by the Dfi.
ren Metal YO rks

2E the German Empirej uader the patent rmnbe~ D. 8130, Class 92, on

.- .

before the sale @f ~ie right of

october 8, 1909, and cor.~equelltl.y
mlanufactxme to any Foreign cm.mtry.
The claim that the English du~alu@.rl differs in its composition
from the German dura,lumin, is inconclusive.

The English ma-nu.f

ac-

iriv
entor, Alfred ?;ilrn
of B erlin, as I have pwven

by many analyses.

The process of manufacture ha..s

been patented in nearly all
ilized countries.

CfLV-

~jickers Sons and Maxim, Ltd. , London, obtained the

pat ent rigiltsfor England from the inventor in 191O, and begs..nto
manufacture duxa,lumin in Bimingharn i-n 2-911. This firriceded tine
French rights to the 11
soci& e du Dura.luminli{Duralumin Company) in
Dives.

The American patent vas confiscated during -theVorld War

of
s.nd-the rights of ma-nuf
acture were given to the Aluminum Cofilpail:r
the
America, The International Ahuninu.m Company in Detroit anil.
Baush Machine and TOO1 Company in springf ield~ Mas sa~husetts

pat ents were taken out in Denmark, sweden, NO r~lay,s~-~itzerland,

The war prevented the taking

HOlland., Belgium and Aust ria-HUngary.

,,

out of pateiits in Russia aiidJapan.

Japan is said to have been

making duralurnin for seinetime in Osaka; and Russia in MOSCOW.

Foreign manufacturers, without exception, call tbei~ products l]dur.

alulain.
Tkere is already a coilsiderable l-iterature on duralurfiin,
both in Germany and in other countries.
The process of manufacture was no chance discovery, but the
.,
result of many years of research in a well-equipped labo~atory

N.A.C.A. Technical Meimorandtlm~Jo*224

(Zentralstelle ffirwissenscha.ftlich-technische ~ntersuc~.rngenj for

sc~entif ic ~ esearch.in ~reuoahel
sberg near Berlin, in ~;hich the inventor, Alfred ,:,iilm,
was linesuqezintendmt

o f the metallurgical

secti.
onO
In 1903 linetask was given to this iilstitu.te
by one of its
Factories of Berlin and M:=.
rlsruhe,
founders, the Germa,nWar ~.~.nifj.on
to find an

dtm~iwm

hand firearms.

alloy

suitahle for making ~artridge cases for

The discovery o f duraluini-n?:as.zm.xnounc

ed in 1909

and was patent ed in 1912 under the number DRP2M554.

To what ex-

tent duralumin sa.ti

sfied the requirements will be explained lai eron the retirement of professor Stribeck from the directorship
of the institute in 1903, the metallurgical section was discontinued.

Engineer Alfred Wilm took over all existing patent rights

and the D&ren Meta1 Works obtained, as the successor Of the GerMan
War Munition FactOries, the imaufacturing rights, under the patent
DW244554,

for Germany, Scandinavia, Holland, Belgium and Switzer-

land.
The pate~t, D;..R.
p.244554, reads: 1
A nroce
,
ss foT making aluminum alloys containing ma~nes ium, characterizeil by the fact that
the alloys, after the last heating in tinecourse of manufacture,
are exposed to terrpezatures above 420C (78801)and then left for
E?+

some time to autgmatic

ii?lpl?ovelilent.
II In,tinec@.scr,iptionit is
.-.
stated that the alloys, aft er being 1:.
ea.t
ed, should be allowed to
cool slowly

It Ynen says:

,. .-.

]T,A.C.l=.
Technical Memorandum No. 284
. .

1. That the aluminum alloys, to which the process is applicable, must contain ragnesiuii;
2. That the alloys must undergo a special thermal treatment at
above 420c (788F);
3. That this final heating must follow the last thermal treatment required for shaping;
4. That the final heati,ng rust follow immediatelyafter

cooling

(either in the air or by plunging in water);

5. That the material, after being thus treated, must be allowed
to rest for some time;
60 That moderate shaping is allowable before seasoning,but
more violent shaping is inadmissible, because it impairs the
product;
7. That the tempered material must be only moderately heated.
In the description, attention is also called to the favorable
effect of small additions of heavy metals, like copper, nickel,
titanium and manganese on the strength of the alloys.
The process is applicable to alloys consisting only of aluminum and magnesium.

Such alloys are made in the D~ren Metal Works

and it is by the comparison of their properties with the properties

of pure aluminum that the effect of the small addition of magnesium is most easily perceived, because, in this case, the effect of
no other components, like copper and manganese, has to be taken
into account.

It would, however, take us beyond the limits of the

;.r

*.
..

,
5

X.A. C.A. Technical IJexomndum No. 284

present article to discuss all these alloys and I will therefore

ccp.f
ine myself to the imoSt iqo rtar-lt
du~a,llxminal 10 ys for indust Yial
,..
purposes, which contain copper and manganese, in ad.dition to aluminum and magnesium.
I
properties.
The w.etal wozker would prefer to errplo
y as few al ioys as possible, but the problem of finding a universal. alloy, combining al-l
the desired properties, must remain unsolved.

In orde~ to meet the

various requirements, he mnst make several duralumim alloys, differing but slightly in their content of copper and manganese and all
having the same content of 0. 5% of magnesium.

The copper content

varies between 3,5 and 4,E@ and the manganese content between 0.25
and 1%

BO th copper and manzanese add strength, W t rnanganese in-

creases the hardness and decreases the cap,acityfor bending and

shaping, so that the amount of wangane se which can be advantageously
added to duralumin alloys is necessarily small.

This is unf ortuna,te,

since manganese is the component which gives Wxa.lumin its relatively

high resistivity to the action of the weather and of sea mater.
These alloys, when cast in sand, exhibit no better properties
than the older, zinc-containing, aluminu-m al 10YS commonly used for
castings=
a.

They can not b e tempered and, for this reason, duralumin

is--not prepar cd-i-nthe form of castin,gsEven chill-mold castings, which have a finer t exture than sand
castings, are scarcely affected by heating and cooling.

Only in

very thin sheets, which have no practical use, does tempering pro-

:T,
A.c.:A. Technical ~emo~andum No. 284
2Uce any noticeable effect.

If tempering is desired, the metal must

o.. 03 given, while hot, a thorough prelimin~.ry forging, rolling, or

pressing.

The mo~e thoroughly this is done, tine.grea.ter

will be

the gain in strength from the final heating md

cooling.

Many forgings, smaged pieces an-dhot-pressed sections require

no supplementary cold treatment.

On the other hand, sheetsand

strips, which often need to be thin, and tubing and wires must be
rolled or-drawn cold, after being worked hot.

These products can

therefore be previously tempered, if they have the proper thickness.

Since an increase in strength and hardness is possible at

the cost of ductility, the metal sheets, strips, wires and tubes
are subjected to moderate compression or tension after tempering,
if a greater strength and nardness is desired than can be obtained
by tempering alone.
In referring to the patent description, I stated that the ma
terial could either be cooled rapidly, by plunging it into a liquid,
or allowed to cool slowly in the air.

The first method yields a

stronger metal and should be employed, unless the metal is very

thin, so that it cools quickly in the air and would be greatly distorted by plunging into a liquid=

It should be remembered that the

breaking strength of the air-cooled. metal is from 3 to 4 kg (6.6

millimeter than that of the liquid.
.= \_ to 8*8 lb.) less per square
cooled metai.
Heating for the purpose of-tempering is best accomplished, in
a salt bath.

It may, however, be done in a muffle furnace, but the

I
N.A. C.A. Technical Memorandum

NO.

284

salt batin affozds the best guaranty of untform heating.

The 1 ength

:Jf the heating depends on the t-tiickness~f th-eobject to be ten~ >equire aocmt 15 minutes and thick-walled obpered. Thifi sh~;t
jects about twice ~.slong.
(932F) .
will

The patent mentions

The be s-t%efi?pera-ture
is about 500C
a ie~ering

he~~

of

qaooc

(7fj80~)

exnlain lat er why this lo~vertemperature was given.

The strength, haTdne ss and ductility are the same, wh etlnerthe

tempering is d-oneon hard-rolled or annealed obj ects.

obj ect can be annealed- and retempered inilefinitely.

A tempered
The tempered

metal always exhibits the same chazacteri stits, nrovided the degrees of heating and cooling were the same.
The three abo-re-mentioned alloys, sold u-nd.erthe designations
681B 1/3 , 681B and ~, have, in the rolled and annealed condition,
breaking strengths of 22-24 kg/mmz (31292-341-36 lb. /sq. in-), with
12-15% elongation and a hardness of 60 to 65 by the Brinnell balltest.

These are noteworthy characteristics in comparison with pure

aluminum which, in the annealed condi tioil,has a breaking strength

of only 10-11 kg/rm2 (14224-15646 lb. /sq.in. ), with 35% elongation
and a hardness of about 28 by the Brinnell test.
coldroll ed pure alur,?irumhas a stren.gthof about 16.5 kg/mm2
(2346,9lb-/sq. in.) at its limit of elasticity, 20.5 kg/mm2 (29158
lb. /sq. in.) breaking

streng~.1>

S6%

elorgption and a hardness of 55.

- The three above-mentioned alloys, aftertempering and seasoning,

have the strength cha.racteris~ics exhibited in the following table:

};,A.
C.A..Technical Memoraridum NO 284.
Strength Characteristics of Duralumin made According to
the Gerr,anpatent NO. 244554.

Delivery

Elastic
I
limit + 20~ ~
remaining
el.ongatioil
kg/mm 2
lb./sq.in

condition

Tempered
681 B 1/3
Cold+pzessed
HaWbiess 1/2
Tempered

681 B

per cent

38 to 41
54049-58316
40 to 44
I 56894-62583

18 to 21
14

Cold-pressed
Hardness 1/2

27 to 29
38403-41248
33 to 35
46938-49782

41 to 44
58316-62583
44 to 47
62583-66850

grosssection
d-ecrease*
Per cent

Impact
I Brinnell I
tkst
b~ll test
cm-kg/cmz
for
in.-lb./i2.2
hardness

18 to 30
mean 26
12 to 28
mean 22
15 to 30
mean 24
11 to 27
mean 19

140 to 158
784.0-884.8
13-5to 145
644.0-812.0
132 to 149
739.2-834.4
105 $0 116
588.0-649.6
.
100 to 115
560-0-644-0
. .
88-tioloo
492.8-560.0

Temperedz

681 B 1/3

kg/mm2
lb./sq.in.

38 to 42
54049-59739
43 to 46
61161-65428

Cold-pressed
Hardness 1/2

Alby

Elongation
t=:ll.3~

26 to 28
36981-39826
32 to 3.4
45515-48360

681 B

24 tO 27
34136-38403
30 to 32
42671-45515

Breaking
strength*

14 to 28
mean 22
.18to..23.
mean 18

. ..

115
122
118
125

18 to 20
12 to i5
17 to 19
10 to 14
Modulus of
elasticity
kg/ cm 2
lb./sq.in.
65!3000 to 7200009245275-10240920
II to
If
11
II -.

710000 to 74000010098685-10525390
1!
II to
n
n
--

120

II
II

128

II

II

* The higher values were obtained with thin samples.

16

*O

to
-to
.-

l
If

II
11

...

----

--

~he upper lines give th-~ strength chara.cte~i s-ticsof the sim-oly
tempered metal, mhile the lower lines show how these characteristics
,..
are increased by a sim:.1
cold.
compression, which we designate with
:1 h~rd-ne

ss

i/~

I! .

~h~-.e

are equal to the stren@h

characteristics of

good ingot iron.

Strength aildhardr.ess cm

be considerably increased at the ex-

pense of elongation, the strength of alloy 681 B, e.g. , to about

50 kg/mm2 (71118 lb./sc~.in,) at the limit of elasticity and 60 kg./
mm (85341 lb./sq.in. ) breaking strength, witinabout 3~~elongation
and a hardness of 153.
Before the announcement of the D R P 244554 in 1909, neithez
scientists nor practicians ever imagined that ailoys containing
OV er 90~ alu-mi
iflUITJ,

idtln

would ever be produced.

such remarkable strength character stits,

The higke s~strength characteristics up

to that time had Iikeri se been obtained- oya process originated by

the 1
zentralstelle ffirvi csenschafil.ich-technische Untersuchungen!l
at lJeubabels-~&rgand protected by patent DRP 170085.
teristics were:

These charac-

after tempering, about 28 kg/mm2 (39826

lb. /sq. in.)

brealiing strength with 204 elongation; after rolling, 32-34 kg/gm2

(45515-48360 lb./sq.in.) brealcing strength with 4-5% elongation.
The process made known by the DRP 244554 patent is a discovery of
extraordinary importance for metallurgy and, though it is now
>uL-

known that magn~sium can be replacedby other metals, the fact re

mains that, in order to obtain such good results, we still haVe to
employ the processes first made known by the above-mentioned pat-

Wlt .

I doubt whether it w~.11 e.rer

oePO ssible to d: spense with

,-~heseprocesses in the production of hi gh--~radeall.1~.lirll~m

alloys

We are not vet sufficien-tlyacquainted with the struttural

changes which occur in metals l.with
the
pictures furnish only

sllght

clues.

lapse of time.

Microscopic

I will S:%PIY SMW

ycu tod-ay,

by means of two examples> the course of hardei~ing duzinq the process of tempering.
The experiments, forming the basis of Fig. 1, were perfozmed
with rolled samples of alloy 681 B, which mere cold-rolled, after
being heated to a,bou-~
300C (572F) .
hardness before heating.

The samples all had the same

They were first heated ,in an oil bath,

then in a paraffin. bath and, lastly~ in a sa-itba th.

.

were in each bath for about 20 mi~nutes.

The samples

They vere not liquid-

cooled, since the object of the experime-ntswas simply to determine

the effect of heat.

Invmed
M tely afteT the cooling of the small

samples, the resulting ha~dne ss was t-eterminetlby th~e e ballt ests

and, after seasoning for 15 days, the tests weze repeated.

The

hardness increased between 100 and 180 C (212 and 356F) and then
i- ..

decreased to about 300C (572T) . Between 300 and 350C (662F)

....
there was no considerable increase nor decrease in hardness. The
best annealing temperature for the tested alloy lies within these
limits.

up to 350C (662F) tileimmediately determined hardness

--

..
N.A.C,A.

Teuhn.ical M&floTa,ndLu.m

No. 284

11

was exactly the smrneas after

~b.er
e wa,
s i-a.pid
iilcrease ii~hardness ?nd the difference between the
hardness, as determined immediately and then after five days, rem,j.ned nearly constnnt up to 520Cc (968 Fj , which gave nearly the
r;nxi.m&Ll
hard-ness. At 420C (788F) tl~emetal had tilesame harclness
as before heating.
Up to 360 C (680F) there was a.d-ecrease in hardness similar
to that observed in o-thermetals anclalloys, but at this point the
small addition of magnesium caused a reversal of the hardness curve.
~leating above this point greatly iil~reas~~ the hardness and strength,
with still fu~ther increases duri-ng -tF.e
five days of seasoni-ng.
FiS. 2 shol;sthe course of the hardening for the different time
intervals. The axis of the ordinates gives -thehardness aecozding
to the Brinnell method.

Theaxis of the abscissas gives the season-

ing time in hours and da-]s. The hardening proceed-s rapidly for the
first four hours.
to 108.

During the first 24 hours i t i-ncyeases from 76

It reaches 112 at the e~]dof the second day and continues

to increase slightlj~up to the end of the fifth day.

If it is de-

sired to obtain a uniform product with the maximu-rnstrength character sties, no manipulation requiring much change in form must be
undertaken before the seasoilingis completed.
~..

The strength curve-is simik.r to the hartlne~s curve.

In urgent
..4,
cases it is not necessary to wait five days, since the seasoning is
nearly complete at the end of two daysz
ceptional, however.

such cases shoulclbe ex-

.,.,

1.2
.

,.,

Dura~umin is p~oduced in the form of sheets, strips, washers,

~~ds, tubes, wires and caties;pressed, rolled.and dravvn sections;
fcrged and pressed pieces; rivets, nails and pins; machine screws
and

wood screws.
In addition to the strength characteristics given in the fore-

going table, duralumin has the following physical properties.

The

specific grav~.ty of the alloys under consideration is about 2.8.

Its coefficieilt of linea~ expansion is 0.000026.

Its heat conduc-

t ivity is a~out 35$ of that of pu~e copp&.

The malleability of duralumin is good.

The best forgi-ng tem-

perature is about 470C (878F). A simple practical method for

determining this teinperature is the glowing of paper or sawdust
brought into contact vith the metal,

Dllral-uminhas no critical tem-

perature, like malleable brass containing less than 60% coppers

The forging inay therefore be long continued without risk.

Swaging

requir,esmore operations ihailiron or brass, because dux~.lumin is

shaped with difficulty.

The heating is done best in a small muf-

fle furnace, but can be done in a forge fire of cokeb

stamping, drawing and bending of the tempered duralumin in the
cold condition are possible within certain limits, but are diffi.~=
cult in compari s~fi--
With soft steel and brass.
avoided.

SharP edges Ust be

The radius of bend should not be less than thrice the

thickness of the sheet,

The malleability of duralumin e.t 300-350 C (5?2-662F) is ~oo?.,

Ikis kind of -norking necessitates, however, an,Gtln
er teqperiilg of the
iici shed articles.

Large cons~l.mers
of dural-~min therefore have

t.he~r owi~ salt l?atlnsfor this purpa se.

Iiea-tingthe tempered duralumin above 18Cl
C (35GF) decreases
the strength.
about 50~.

At 3G0-350 C (572-~62F) the strength is diminished

.:.

A st:arpsupervision of the workmen, to preveilt their

misuse of the soldering lamp iilsheet-metal work, and frequent instruction of tne superintendents and workmen, on the unfavorable
effect of l?eating, is desirable.
Duralumi n can ~e

i.:{e~d

ed

and

so

Id-eTcd.

Even in the ~ost favor-

able case, however, the meld is only about half as strong as the
rest of the metal.

~heductility
of the seam is small ar.dva?iable.
.

In the nei~~~orhood of the sea:m~which is produced at a temperature

of about 650C (l?02~), the~e is a region in which the metal had a
ternperatureof 300-350C (5726620P) , and was therefore annealed=
A duralumin wei.dhas the structure of a casting and can not
be strengthened by subsequent hammering and tempering.

The welding

o r soldering of duralumi n should therefore be avoided and unions

should be made with rivets or screws (Compare 1
Zeitschrift ffir
Metalllaand-e,
11923, vol. 15, p.286) .
RiVet5 are made from a special alloy having a shearing strength
,,.
.
of 26-28 kg/mmz (36981-39825 ib./sq*in. )- Rivets for parts coming
in contact wi th sea water~ like seaplane

bulls

and floats, must

have, as nearly as possible, the same composition a.s the neighbor

T,!..
C.A. Technical Memorandum NO. 284
3 rig metal,

1.
~

In oN. erto prevent *>Aedeterioration of the zivet head.~

-Ijhzaughgalvanic actiorl.
,
The ciiemical charac-tezisk?.
cs of ~.ll~aiumim.
e.iffer from those of
p~re a,lw.mi-num.ThiS SUbjICCtdoes nOt Y howeVe~, collle.
~~ thin the
,?cqe
Ii.

of tb.epresent arti~le.

I t is not ewmr-~hytha.t duraluminj un-

ke pure aluminum, is not readily affected oy mercury.

The r~sist~nce of d-ura,luminto the corrosive action of sea wa-

ter is relatively good.

it is better than that of any other known

light metal.. iron in comhin..ation

with dura,lumin protects the latter from the action of sea water=

Detai2.ed sxperiinents, Wade by

the B erli-nMunicipal Departtient for H ygi =Li.

and Economic Res e~.rch,

d=monstratecl that duralumin is not injurious to health and is there

fore suitable for the manufacture of cooking ut ensils.
The resistance of &~ralu~il~.n
to atmospheric action is goodThrough experiments cove~:i-nga period of abou t five years, it was
found that specimens in the form of rods of 10 mm ( .39 in. ) diameter,
flat ~ars of 5 (.197) and 2 mm (.078? in. ) thickness and mires of
ty
5 a-rid
2 nm diameter suffereclno loss in strength and d-uctili

They hung the year round-on the roof of one of OUT factory buildings
exposed to al?- sorts of weather.
The strength and ducti lity of duralum.in are. favorably affected
...

the freezing.,
poini of waterby temperatures.b elol~i
creases l.~ith
decreasing termperawre.

The strength in-

In an experimerit at -190 C1

(-310F), the strength was found to have increased from 42 kg/mrn2

to 53 kg/mm2 (59739 to 75585 lb=/sq. in. ) and the elongation from 22
.

~!;
A. C.A. Tech.
nicL.lMemoranchm

?To.

284

Lo2s?.. The shock strength.reifi~

ined unait ered.
t~nt in aircra,ft constriction.
1 have made a series of f~tigue tests wi-tin
du~~.lumin and will
p~~olishthe results duriilg -tIhe
summer in the ll~eit:;ch.rifi
f~-c~Ietall.
kund e.r! I will only mention here that,duraluain grove,
better results
thail soft steel, pho s-p.hor-bronze(CWgz sn2s ),

a..ndJ
tombakll

(Cu72 zn~e).
Uses.
-.
..
In the spring of 1914, the navy and$ subsequently, the militaxy
administration stipulated the ex~l-usiveuse of d~rs.lu.tnin
in the construction of ~heairshi~s ordered of the ,zep-oelin
Company at FTiedrich shafen,
alumin.

Thus a new

a,ind

very large market was -provided for dur-

The whole framevrorkof the airships vas made of duralumin

in the form of thin

bracing strips.

~,ncl
angular sections and- still thinner

During the war we supplied ihe material for more

than 80 airships, over 750metric tons (1653465 lb. ) in one year.

when, during the course of the war, the building of airs~.ips
for the army and navy m.s reduced, metal ai rpl.anes came into use
and the demand for duralurfiinfor this purpose inc~eased greatly d-uring the last year of the war.

A g~eat deal of duralumin is still

-tEedevelopment of
used in building airpl,anes. Ur.fortu.nate?.y,
German air-planecoilstruction is restricted ~y the Treaty of Versailles
to the production of commercial ~irplanes of a certain size and speed,
thus reducing the demand- for mateyials.
There is am increasing demand- for duxaluuin for the connecting-

H.A.C.A.

Technical Memorandum ITO.284

xods of automobile internal comhtistio-n

it has tb.
e fo1.
lo,~jir.g
aiivantageg:

5. A greater clinbiilgcapacity on mountains;

6. Rapid dispersion of supe~fIuous heat;
-)
1.

Less pressure on the bea rings and co:nseq-r.

ent le ssening of
friction;

8.

Wre.ater ease in

9.

Greater

starting

engine;

elasticity of engine;

7.0. Smootlner functioning of ergine, with less vibration, and,

conseq-~ea~ly,
1?-*Longer life cf both engine [m<.vehicle.
Duralumin is a,lsoused. for other eagine -!~artsand in the construction of automobile cb-assis a-rid
bodies.

The Zeppelin Boat Yard

extensively in the hul.l.s

at Staaken, near pot sclam,u ses dur~.lu.mi-n
of boats and also iilthe body of a mall

moto~ car.

Du ra.1.umi
n is

employed in ce-ntrifuf;almachines, opti cal instruments, el.

ectrica.l
and orthopedic appliances, compressors, magnetos, life-savi-ng appa--~~~ratus,- jewelry, etc. -

The previously nentioned obj ect, which led. to the M scovery

of duralurnin, namely, the production of a.suitable alloy fGr the
manufacture of cartridge cases, was only partially successful.

., ,

,,, ..,,

,,. .

..--

The

.. -.,...
-ly
..

N.A.c.A..Technical l~emoranduiiNo. 284

German War Munition Factories in Karlsrihe made duralumin cartrid~e

M.

cases which were capable of being fired and which stGod the test of
a ten-de-ncy,
however, to turn through at the
Stori-ng. They sb.owed.
base.

Since this seriol.~s

defect is due to the low melting point

of duralumin (650C or 1202 F) which can not be raised$ the prospects for duralumin cartridge cases are small.
I prophesy a great future foz the aluminum alloys made ac coYding to theGerman paten-t 244554,

but

this future lies in other

fields, which can only be concluered.

by pati en-tand persevering wozk.
Rivets.l~ade from
Aluminum-A11OSW.
.
At the request of the Bureau of Aeronautics of the ~.~e~ican
Navy, the properties of rivets made from aluminum alloys were thoroughly tested (See

j?OU?Y.dLIy

Trade

Journal., 1923, Tel. 28, p. 333)

con-ipositions:
The analyses of the samples skewed the f-ollo~-~ing
.

Percentage Composition of Rivets.

2

e,.

0.89

,,, *. Or
. traces.

Metal

0-28

Fe

0.52

0-52

0.54

Mg

0.00

O.00*

0.14

Al

Rest

Rest

,,.

It is, therefore, not necessary to employ very soft rivets of

nearly pure aluminum, since good results were obtained even with
cold-drawn and annealed wire made from an alloy containing 3~oof

~.-A.d.A.

!J?echnical~Jemorand.umJTO.284

18

i;.

copper,

20~ zinc

n mire.
and.77% aluminum, or wi th dure.l.-dmi

~ivets

]Iia,de
from these al-l.oys
are better tha-nth-osemade fzom pure aluminum wire, since they have a Sreater sheariilgstrei~gth. After being
in

use

many

months, they have shwn

no tears nor other defects.

Rivets made from cold-:trawnl~i

re, corm-o
sed of 3$ W-, 20$ Zn
and 77% Al, a-nil
he~,ted to 250C (W2F)

have the greatest shearing

strength of 270 kg/cm2 (7840 Ib.,lsg..

in. )z while values of 200-220 kd
cm (2845-3129 lb ./sq.in. ) :]e~e
obtained with rivets made from hotdra~,~nduralumin ~~ire.

The first-mentioned ril-etsare preferable>

because they may be used at any length of time after the thermal
treatment and do not require retempering.

puralu.min rivets shoulcl

be used as quickly as PO ssible aft er tempering and-aTe comiS~.rati-~elY

difficult to tighten=

Tb-is difficulty may be remedied by e-mployiilg

a some~~llatsofter aIIOY (2-25$ GU, o%

u%

96c75% Al, OW%

~n)

which xeq.uiresa thertn~l treatm e-ntsimilar to that required by duralu.min.

Translation by iwight 1.1Miner,

National Advisory Comiilitt
ee
foz Aeronautics.

$STs-.

Fig. 1

N.A. C.A. Technical liemorandum No. 284

,.,

OF

392

212

572

752

932
c

110
105

100

95 ~
0
90

&$... -..
-----,,<:+
g
,..../

85
--l-.

80

,~: #Q
~;,..,,
;p+
.~;~$ i
// ,,@ ./
~
. ,,,/,~, :c

.:f~~
.* ,/.

75
70 l---+--+--+-+---+
65

100

j-+-=
200

Oc

300

400

500

Fig. 1 Brinell kardness. Breaking streilgth 40.4 kg/mm2

(57463 lb./sq.in.) Elongation 10.1 %. Ccurse of
heat curve of an aluminum alloy containing magnesium. Thermal effect without cool.imz i.nIicuids.
Br aking st~en th of cold-rolled shee-i:u=34.3k2,/
mm~ (48787 lb. 7 sq.in. ) Minim~l.mtempe::irg te;:perzture.
Elongation 2.9 ~ Curve C-C.-Cf 33.2 % JJ.O.52 % IIK
4.28 ~ CU,l.07 $ Mn treated according to-pa,ten~ Dfi
244554

N.A. C.A. Techriical Memorandum No. 284

115.

Fig. 2

i,1

.~.

110
100

95
90
85 /
on

70
65
024

Fig. 2

+
1924

48

72
hours
Seasoning period

96

120

Effect of seasoning. Brinell ha~dness. Alloy containing 4.5 fO CM and 0.57 % Mg, Effect of seasoning
period on hardness of tei:lperedduralumin.

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